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HOOL HOOL—ELEMENTS OF STRUCTURES 188 pages, 6 X 9, illustrated HOOL—REINFORCED CONCRETE CONSTRUCTION Volume I—Fundamental Principles 245 pages, 6 X Q, illustrated Volume II—Retaining Walls and Buildings 666 pages, 6 X 9, illustrated Volume IlI—Bridges and Culverts 688 pages, 6 X 9, illustrated HOOL AND WHITNEY—Concretete Drsianers’ MANUAL 327 pages, 6 X 9, illustrated HOOL AND JOHNSON—ConcretTE ENGINEERS’ HAND- BOOK 800 pages, 6 X 9, illustrated HOOL AND JOHNSON—Hanppsoox or Buiupine Con- STRUCTION Two volumes. 1474 pages, 6 X 9, illustrated HOOL AND KINNE—Founpations, ABUTMENTS AND Foorinaes 413 pages, 6 X Q, illustrated HOOL’ AND KINNE—Structurat MEMBERS AND Con- NECTIONS 611 pages, 6 X 9, illustrated HOOL AND KINNE-—Srresses IN FRAMED STRUCTURES 620 pages, 6 X 9, illustrated HOOL AND KINNE—STEeEEL Aanp TIMBER STRUCTURES 695 pages, 6 X 9, illustrated HOOL AND KINNE—ReEtnrorcep CoNcRETE AND Ma- SONRY STRUCTURES 722 pages, 6 X 9, illustrated HOOL AND KINNE—Movas.e anp Lona-sepan STEEL BRIDGES 450 pages, 6 X 9, illustrated HOOL AND PULVER—Concrete PRAcTICcE | oe wes = ‘< 30: oie whips “4 Aes: a a oF ‘UUdT, ‘O[IAYSVN 7B UOUEY}IVg UIUSyLV oY} Jo vor[dor ojo1NU0D poolOsUIEYy (a901d s1.4U0LJ) CONCRETE PRACTICE A TEXTBOOK FOR VOCATIONAL AND TRADE SCHOOLS BY GEORGE A. HOOL, 8.B. Professor of Structural Engineering, The University of Wisconsin University Extension Division AND HARRY E. PULVER, B.S., C.E. Associate Professor of Structural Engineering, The University of Wisconsin University Extension Division First EpIrion McGRAW-HILL BOOK COMPANY, Inc. NEW YORK: 370 SEVENTH AVENUE LONDON: 6 & 8 BOUVERIE ST., E. C. 4 1926 CONS TA GSI Were. 726 CopyRiGuT, 1926, BY THE McGraw-Hitut Book Company, Ino. PRINTED IN THE UNITED STATES OF AMERICA ee ) e 06 66 eeseos89d a eooee igs » eo @ e 6 08 aee ce asoee ‘ - eee es, ® o® a? e . eeeoe A Ets o%%% e s Sy55°% 5y%%e98 Cd 2 aeaed e°. e 5 @ e es od 28 °) 6 es “9 $s “se os #08 e 2 eeved @ Ss eeeee : oe 8 © eet 8Ve e ~ s r) Lah hae °o.%se eos ax? a M4 e we eusve o* eeu 2 6 ) ~ weve es ) my ~ THE MAPLE PRESS COMPANY, YORK, PA. PREFACE The authors have attempted to present in this book such material as will be suitable to the needs of students in vocational courses and it is hoped that this material will also be of value to many men engaged in concrete work. Attention is called to the exercises and problems accompanying practically all of the jobs throughout the text. It is thought that these will be of assistance in teaching the subjects treated in this book. Laboratory and field equipment and the time available will usually not permit all of the jobs in the text to be assigned the student. The authors have included a large variety of jobs so that the instructor can select and use those which will be suitable. G. A. Hoot. H. E. PULveEr. Mapison, WISCONSIN November, 1926. 189990 vil CONTENTS PREPAC GAS cla Section I. FUNDAMENTAL CONSIDERATIONS Composition and Knowledge of Concrete . Cementing Materials. ...... Portland Cement. ae Me gare Manufacture of Portland Gren parte Noe; Properties of Portland Cement. eet, Portland, Cement Mortars ........ Fine Aggregates . Coarse Aggregates . i Ae Water for Concrete Mixes... . Properties of Concrete. A Effects of Various Substances on Copcrate. Section IJ. Prororrionine, Mrxina, AND PLaciIna CONCRETE Job 1. General Theory of Concrete Proportioning ..... . teeny Job 2. Proportioning Concrete by Arbitrary Proportions ..... . Job 3. Proportioning Concrete with Reference to Voids. Job 4. Proportioning Concrete by Sieve Analyses of the Angregstes and the Maximum Density Curve. Ai NaN es . Proportioning Concrete by the Surface Area Method. ; . Proportioning Concrete by the Use of the Tables in the 1924 Report of the Joint Committee ...... Job 7. Proportioning Concrete by the Water-cement Hatio | Sian Test. : Job 8. Proportioning Coitarets iss a W avercemenré Hato. ‘Slump: and Fineness Modulus of Aggregate... .... Job 9. Illustrative Example of Proportioning Concrete by che Water, cement Ratio, Slump, and Fineness Modulus of Aggregate . Job 10. Consistency of Concrete ..... Job 11. Measuring Concrete Materials . cee BSS dX Job 12. Computing Quantities of Materials for Concrete 2 ont Os Joo 1a, tana) Mixing of Conerete...°.. .. .. Sh AAS eto tea! Job 14. Machine Mixing of Concrete .... . Job 15. Concreting Plant... ; : Job 16. Transportation of Concrete. . Nak etek seis Job 17, Depositing Concrete in Forms. ....... ix Job Job o> 1 43 Job 52. : Job 53. CONTENTS . Bonding New Concrete to Old . ... 3... > ss. ee 170 g. Passing No. 50 sieve. ..9:........... eee 82 g. Passing No. 100 sieve...) .. 2... «a0. 2 4 ee 12'¢. Plot a sieve analysis curve for this sand on a sheet of cross-section paper, plotting percentages passing as ordinates (vertically) and sieve openings as abscissae (horizontally). Does this sand pass the specifications for the grading of a fine aggregate given in this article? Compute the fineness modulus of this sand. COARSE AGGREGATES The coarse aggregates commonly used in concrete are river and bank gravels, crushed limestone, granite, trap rock, blast fur- FUNDAMENTAL CONSIDERATIONS 13 nace slag, and cinders. The gravels frequently contain dirt, silt, and sand, and often require washing and screening before being usable. In general, a bank-run gravel should not be used in concrete unless it has been thoroughly tested and found to be satisfactory. It is usually necessary to wash a bank-run gravel and then screen out either its fine or its coarse material. When available, a good gravel is a very economical coarse aggregate for concrete. Crushed limestone, granite, and trap rock are all good for a concrete aggregate. A good, crushed-rock concrete is frequently a little stronger than a gravel concrete of the same proportions. Rocks such as shales, most of the sandstones, and very soft limestones are unsuitable as a coarse aggregate. Cin- ders of good quality have been used as coarse aggregates where light weight rather than strength is desirable. Blast-furnace slag, with a low sulphur content, may make an excellent concrete aggregate, but, because of its porosity, it should not be used in thin sections which may be subjected to water action. Visual inspection of a supply of coarse aggregate will give a good idea as to the mineral constituents, uniformity of supply, and approximate grading of the particular aggregate. The presence of dirt, clay and silt in the coarse aggregate may also be detected. In general, any crushed stone or gravel is suitable for concrete work that is durable and strong enough, so that the strength of the concrete is not limited by the strength of the aggregate. Desirable properties are density, hardness, toughness, strength, durability, grading, and cleanliness. The best coarse aggregate for concrete work, as to grading, is one that has a comparatively large fineness modulus and a small percentage of voids. For massive concrete work, the maximum size of the particles may be 2.5 or 3 in., while in reinforced concrete work the maximum size may be 0.75, 1, or 1.50in. ‘The coarse aggregate must not be so large that it will not work freely around the reinforcement and into the crevices and corners of the molds and forms without extra tamping and rodding. Of the igneous rocks, granite and trap are suitable materials for coarse aggregate. Of the sedimentary rocks, compact calcium and magnesium limestone make excellent coarse aggregates. A very soft limestone, or a limestone containing a large percentage 14 CONCRETE PRACTICE of clay, will probably not prove to be a good material for concrete. Most of the sandstones do not make good aggregates, because of their tendency to disintegrate. Some sandstones, in which the cementing material is lime carbonate, have been successfully used as coarse aggregates. Gravel which is clean and of a good mineral quality is a very satisfactory concrete material. Crushed rocks or gravels containing particles of clay, shale, or mica, or having thin, elongated, laminated, or friable pieces do not make good concrete aggregates. The percentage of voids in common crushed stone and gravel varies from about 30 to 55 per cent, depending to some extent on Fercentage Passing Sieve =S x= Water Cernent RaH0 Water - gallons per bag of cement 300 ae 450 $25 6.00 675 750 825 900 975 /050 Fria. 3.—Relation between the compressive strength of concrete and the water 50 60 70 80 .90 100 110 120 130 140 150 0 cement ratio. 14,000 proportioning, mixing, placing, or curing, the number 7 in the formula should be replaced by 9. This strength formula then becomes: FUNDAMENTAL CONSIDERATIONS 19 The curves in Fig.°3 show the relation between the unit 28-day compressive strengths and the water-cement ratios by volume, plotted according to the above formulas. Other formulas, which will give practically the same results for water-cement ratios varying from 0.6 to 1.6 (unit compressive strengths varying from 4500 to 600 lb. per sq. in.), are: Ss = _™ = 1700 for good working conditions and 2 ay) S = oe — 1700 for poor working conditions If desired, gallons of water per sack of cement may be used instead of the water-cement ratio. Then, letting g.s. equal the gallons of water per sack of cement, these formulas may be written: S = a — 1700 for good working conditions or 27,700 esis 1.700 and S= 7 — 1700 for poor working conditions or 24,400 eS 431700 For concrete mixes of equal workability, as measured by the slump test (see Appendix 7), there appears to be a relation between the amount of cement in the mix, the water-cement ratio necessary, the resultant compressive strength of the concrete, the maximum size of the aggregate, and the grading of the aggregate expressed in terms of the fineness modulus. This relation is shown graphically by the curves of Fig. 4. In general, the amount of cement and workability (slump) of the mix remaining the same, aggregates having greater fineness moduli and larger maximum sizes will require lesser amounts of mixing 20 CONCRETE PRACTICE water per sack of cement (lesser water-cement ratios), and thus give concretes of greater compressive strengths. be Slump - 3 fo 4-in. Be 8 AN b&b © Re eee es ae {ee Leaee 0) fA i) Roe Oe ee Pa eS ee ~ | Stump 6 40 Pin | | | | | BERR EL. N KR s Ce aoa fo Sa ae es ee ad ee ee Wy us) Real M/x.— Volumes of Mixed Aggregate for each Volurne of Cement S 50 54 58 62 66 70 46 50 54 58 62 66 7.0 72 Fineness Modulus of Aggregate Fig. 4.—Relation of size and grading of aggregate and quantity of cement to strength of concrete. This diagram is based on the relation between strength and quantity of mixing water shown by Curve B in Fig. 3. ; With good curing conditions, there seems to be a fairly definite relation between the unit 7-day and 28-day unit compressive strengths of the concrete. This relation is shown by the formula: Seg = S; + 30S; FUNDAMENTAL CONSIDERATIONS 21 wm oy ee ATE aver % Pel / aha bel > 7A ae ee = QUE ah = Be neavicial Re ees | EN peal ae < PEEL a SaMRnee S “mbaes & Sunngee wv el. ia ~ a a ze i Q : PEE : G @ —_ 528 /000 Af | 74 Sac aetee og aA eee Cee ee ee 0 /000 2000 3000 4000 5000 57= Compressive Strength at 7 days Fic. 5.—Compressive strength of concrete—seven and twenty-eight day strength relation. Revert fe me, | | ray Period of Curing, in years Fic. 6.—Strength-age curve for concrete. 22 CONCRETE PRACTICE where Ses = unit 28-day compressive strength and S; = unit 7-day compressive strength The curve in Fig. 5 shows the relation between the 7- and 28-day unit compressive strengths. The unit compressive strength of concrete increases with age, about as shown by the curve in Fig. 6. Of course, variations in the qualities of the materials used and in the curing conditions will affect the compressive strength, and may give values which are more or less than those shown by the latter part of the curve. Weight per Cubic Foot.—The weight per cubic foot of good sand and crushed stone or gravel concrete varies from about 135 to 160 lb. per cu. ft., with an average value of about 145 lb. per cu. ft. for plain concrete. Concrete made from cinders, slag, and other light aggregates will have a lighter unit weight than the values given. Expansion and Contraction.—Concrete will frequently shrink a little when hardening in air, and may keep the same volume or expand a little when hardening in water. The coefficient of expansion for concrete is about 0.000006 per °F., and this coeffi- cient varies but little for the different mixes and aggregates com- monly used. The fact that a good crushed stone or gravel concrete has about the same coefficient of expansion as steel means that temperature changes will not cause the separation of the concrete and steel in reinforced concrete work. Absorption.—The absorption of water by plain concrete may be comparatively small or great, depending on the density of the mix, richness of the mix, kind of aggregates used, and the thoroughness and care used in proportioning, mixing, placing, and curing. In general, the same factors that tend to make a concrete mix waterproof will also tend to make it non-absorptive. Abrasion.—The abrasive resistance of plain concrete depends primarily upon the abrasive resistance of the mortar, which in turn depends upon the ability of the cement to hold the sand grains together, and upon the abrasive resistance of the sand grains themselves. When the surface of the concrete is worn away, so that the coarse aggregate is exposed, the abrasive FUNDAMENTAL CONSIDERATIONS 23 resistance then depends partly upon the abrasive resistance of the coarse aggregate. Exercises.—Using both curves of Fig. 3, find the unit ultimate 28-day compressive strengths for a mix having a water-cement ratio of 0.90. Fora water-cement ratio of 1.05. For a water-cement ratio of 1.20. If the unit ultimate compressive strength of the concrete was 1770 lb. per sq. in. at an age of 7 days, what would be its probable strength at an age of 28 days? If the unit ultimate 28-day compressive strength of concrete was 2400 lb. per sq. in., what would be its probable unit strength at 6 months? (Sug- gestion: Use curve showing relation of strength to age.) How many inches wouid a concrete wall 80 ft. long expand, when the temperature increases from 45 to 90°F.? EFFECTS OF VARIOUS SUBSTANCES ON CONCRETE Tne effects of various substances on concrete may be divided into two classes: (1) the effect of various substances mixed with the concrete; and (2) the effect of various elements on the concrete. Effect of Mixing Various Substances in Concrete. Azr.—dAir is the most common impurity present, as evidenced by air voids in the concrete. Most of the air may be removed by thoroughly ‘compacting the concrete in the forms. Clay and Silt.—A little finely divided clean clay or silt tends to make concrete (especially the leaner mixes) more water tight and more easy to work. An excess of clay or silt (say more than 10 per cent) may cause a decided loss of strength. Loam and Dirt.—These materials, if organic matter is not present, have about the same effect as clay and silt. As organic matter is usually present in loam and dirt, these materials should be excluded from concrete mixes. Organic Matter.—All organic matter should be excluded from concrete mixes, because as small an amount as 149 of 1 per cent may be very injurious. Lime.—Unhydrated lime (quick lime) should never be added to a concrete mix, as its expansion when hydrating will probably cause expansion and disintegration of the concrete. ‘Thoroughly hydrated lime has about the same effect as clay, and is preferable to clay. 24 CONCRETE PRACTICE Mica.—A very small amount of mica mixed in concrete will cause a decided loss of strength. Sugar.—The presence of a small percentage of sugar mixed with the concrete reduces the strength and soundness of the concrete. Grease and Oil.—These materials have a bad effect on the quali- ties of concrete, when mixed with the concrete materials. Sea Water.—It is not thought advisable to use sea water as mixing water, when making concrete, though recent tests have not shown a very great loss in strength. Salt Water.—Waters, containing more than a few per cent of common salt in solution, may cause a decided loss in strength, and, consequently, salt should not be added to the mixing water. Acid and Alkali Waters.—Mixing waters containing much acid or alkali frequently reduce the strength and soundness of the concrete. Effect of Various Elements on Hardened Concrete. /Fire.— Good concrete is little affected by fire up toa temperature of about 1200°F. (as hot as an ordinary fire). The action of fire is to cause a change in a thin layer of the outer surface of the concrete, and this layer then serves to protect the remainder of the concrete. Aggregates, which will burn or disintegrate under temperatures less than 1700°F., should not be used in concrete which may be subjected to fire. A fire hot enough to cause disintegration of the aggregates will, of course, cause a failure of the concrete. In some cases, the expansion and contraction, due to the application of fire and streams of water, may cause trouble. In general, concrete has better fire-resisting qualities than ordinary building stone, brick, tile, or terra cotta. Frost.—In general, freezing has little effect on good, well- hardened concrete. Freezing and thawing of wet and com- paratively porous concrete frequently cause disintegration and spalling of the exposed surfaces. | Sea Water.—Sea water appears to have little effect.on good, dense, concrete, well made from materials of excellent qualities. Poor concrete, when exposed to sea water, often shows a swelling, cracking, and crumbling of the surfaces. Alkali.—The effect of alkali water is practically the same as that of sea water. FUNDAMENTAL CONSIDERATIONS 25 Oils and Greases.—The effect of various oils and greases is given in Appendix 10. Acids.—In general, good, thoroughly hardened concrete is affected only by such acids as would seriously injure other materials. Miscellaneous Liquids.—The effect of various liquids often found in different manufacturing processes is given in Appendix 10. Exercises.—What is the general effect of the following materials on the surface of good, thoroughly hardened concrete, and what surface treat- ment is recommended (see Appendix 10). Heavy oils? Gasoline? Olive oil? Cider vinegar? ‘Tanning liquors? SECTION II PROPORTIONING, MIXING, AND PLACING CONCRETE JOB 1. GENERAL THEORY OF CONCRETE PROPORTIONING Fairly recent investigations have shown that the strength of concrete depends primarily on the water-cement ratio (ratio of volume of water to volume of cement) of the mix, provided the mix is of a workable consistency. Increasing the amount of cement, or decreasing the amount of water, decreases the water- cement ratio and increases the strength, and vice versa (see Fig. 3). The least amount of water that will give a workable mix will also give the strongest concrete. Both the economy and the workability of the mix are influenced by the grading and size of the aggregate. An increase in the fineness modulus (see page 9) and maximum size of the aggre- gate will usually be advantageous. For example, it has been found that, with a fixed amount of cement and water (constant water-cement ratio), the same quantity of a given aggregate will always be required to give a mix of a desired workability. The same workability may be obtained by using a greater quantity of an aggregate having a larger fineness modulus and larger maxi- mum size. Likewise, the same workability may be obtained by using a lesser quantity of an aggregate having a smaller fineness modulus and smaller maximum size. Hence, for a mix having a definite strength (water-cement ratio) and a certain workability, the most economical aggregate to use is one having the largest permissible fineness modulus and maximum size. By largest permissible maximum size is meant that the aggregate must not be so large as to restrict a free flow of the concretein the formsand around the reinforcement. By largest permissible fineness modulus is meant that the aggregate must not have an excess of large particles so as to make the mix harsh. The amount of the 26 PROPORTIONING, MIXING, AND PLACING CONCRETE 27 fine aggregate in the mix should not be less than half of the amount of the coarse aggregate. The required consistency or workability of the mix will vary for different jobs. For example, a much drier mix can be used for massive concrete work, such as large retaining walls or bridge abutments, than for a thin wall or a reinforced concrete floor. The water-tightness of a concrete mix may be increased by the careful grading of the aggregates and the correct proportioning of the materials, so as to make the resultant mix more dense and to reduce the size and number of the voids. Only materials of good quality should be used for concrete mixes. ‘The portland cement should be one which has passed the standard specifications and tests. Water and aggregates of good quality should be selected as explained in Section I. From the above statements, the following general rules for proportioning concrete may be deduced: 1. Use portland cement, water, and aggregates of good quality. 2. Base the strength on the water-cement ratio. 3. Base the required workability of the mix on the particular job, using as dry a mix as practicable. 4, Add mixed aggregate to the cement and water, to give the desired workability of mix. 5. For economy, grade and combine the fine and coarse aggre- gates, so that the greatest proportion of mixed aggregate can be used and yet have a mix of the desired workability. For years, different investigators have tried to find a general rule for proportioning concrete by which its qualities and prop- erties could be determined in advance. While no such general rule has been found and accepted by all concrete engineers, much worth-while knowledge has been obtained in regard to the proportioning of concrete mixes. This knowledge, intelligently applied, greatly reduces the amount of work required to produce a concrete mix having the desired qualities. The effects on the qualities of the concrete mix, due to varying the water-cement ratio and the amounts and grading of the aggregates, have been fairly well determined. The effects caused by using aggregates of different types and kinds need to be more fully investigated. To quote the Bureau of Standards: ‘‘No type of aggregate such as granite, gravel, or limestone can be said 28 CONCRETE PRACTICE to be generally superior to all other types. There are good and poor aggregates of each type.” Consequently, the best and safest way of determining the cor- rect proportions for a concrete mix using any one kind of aggre- gate is, first, to test the materials to be used, then carefully select the proportions according to the best information available, and lastly to check the qualities of the mix selected by strength and other tests. The methods of proportioning concrete given in the following articles have been used at various times and places. Propor- tioning with reference to the water-cement ratio, consistency, and fineness modulus of the aggregate is the method recom- mended. JOB 2. PROPORTIONING CONCRETE BY ARBITRARY PROPORTIONS This method is the oldest and most commonly used method in this country. The materials are measured by volume, with 1 cu. ft. as the common unit of measurement. One sack of cement is taken as 1 cu. ft., and the fine and coarse aggregates are usually measured by volume in a loose condition, just as they are thrown into a wheelbarrow or measuring hopper. Enough mixing water is used to give the mix the desired consistency, which is frequently much wetter than necessary for the best results. Proportioning concrete by volume, by the method of arbitrary proportions, is proportioning by a rule-of-thumb method which is not justified either by science or good practice. The following are some of the commonly used mixes: 1:1:2 A very rich mixture used where great strength and water-tightness are required. 1:1:3 A rich mixture not so strong as the preceding, but used for the same purposes. 1:2:4 A good mixture, used very often for reinforced concrete. Often assumed to have a compressive strength of 2000 lb. per sq. in. at an age of 28 days. 1:2:5 A medium mixture used for plain concrete floors, retain- ing walls, abutments, etc. 1:3:6 A lean mixture used for massive concrete under steady loads of not great intensity. PROPORTIONING, MIXING, AND PLACING CONCRETE 29 1:4:8 A very lean mixture used only for massive concrete, which supports practically no load except its own weight. Sometimes the proportions of the mix are given as one part by volume of portland cement, to a number of parts by volume of combined fine and coarse aggregates. Some of these mixes frequently used are as follows: 1:5 About the equivalent of the 1:2:4 mix previously given. 1:6 About the equivalent of the 1:2:5 mix previously given. This 1:6 mix is often substituted for a 1:2:4 mix, but con- tains less cement per unit volume of concrete and has less strength than the 1:2:4 mix. 1:9 A very lean mix, equivalent to the 1:4:8 mix previously given. This 1:9 mix is often substituted for a 1:3:6 mix. A 1:2:4 mix by volume is about the equivalent of a 1:5 mix by volume, because most of the fine aggregate in the 1:2:4 mix goes to fill the voids in the coarse aggregate, and the resulting volume of the mixed aggregate is not 6, but about 4.75. The weight per cubic foot of a combined aggregate is invariably more than that of either the fine or the coarse aggregates taken separately. If the proportions were given by weight, then a 1:2:4 mix would be the equivalent of a 1:6 mix, because 1 lb. of cement. plus 2 lb. of sand plus 4 lb. of stone is about the same as 1 lb. of cement plus 6 lb. of mixed sand and stone (exactly the same if 2 Ib. of sand are mixed with 4 lb. of stone to give the combined aggregate). Exercises.—What “standard” mix by volume is commonly used for reinforced concrete work? | What mix by volume is commonly used for basement walls? Show that a 1 : 9 mix by volume of cement to combined aggregate is not the same as a 1:3:6 mix by volume of cement to fine aggregate to coarse aggregate. If a numerical problem is desired, assume the weights of cement, and fine and coarse aggregates to be 100 Ib. per cu. ft., and the weight of the combined aggregate to be 125 lb. per cu. ft. JOB 3. PROPORTIONING CONCRETE WITH REFERENCE TO VOIDS The object of this method of proportioning is to secure a con- crete mix having a minimum percentage of voids, the idea being that, with other things equal, the densest mix (mix with the least 30 CONCRETE PRACTICE voids) will make the strongest and best concrete. It is doubtful if this method of proportioning is of much practical value unless checked by strength and other tests. There are several variations of this method of proportioning of which the following three methods are the most common: | One variation is to use just enough mortar to fill the voids in the coarse aggregate. Due to the bulking effect, however, about 10 per cent more mortar is required. Coarse aggregates having a low percentage of voids permit a saving of cement and sand. The strength of the mix is to be increased or decreased by varying the amount of cement in the mortar. Another variation is to mix the fine and coarse aggregates in such proportions that the resulting voids will be a minimum, and then to add the cement and water. The strength of the mix is. to be governed by the amount of cement added. A third variation (and possibly the best one) is to try several trial mixes of cement, water, and fine and coarse aggregates to find a mix that will be the most dense (have the least voids). It is assumed that this mix will be the strongest and most impervious. JOB 4. PROPORTIONING CONCRETE BY SIEVE ANALYSES OF THE AGGREGATES AND THE MAXIMUM DENSITY CURVE In this method of concrete proportioning, it is assumed that the densest mix can be secured by making sieve analyses of the aggregates (both fine and coarse); and then combining these aggregates and the cement with the aid of the maximum density curve. ‘This method may be considered a variation of the void method, in which the proportions of the densest mix are secured by the help of the sieve analyses and the maximum density curve. After the sieve analyses of the aggregates have been made, the results are plotted on cross-section paper, and a curve drawn for each aggregate. Percentages passing sieves are plotted to a vertical scale (ordinates), and diameters of sieve openings are plotted to a horizontal scale (abscissae). Then a maximum density or ‘‘ideal’”’ curve is drawn. ‘This curve consists of a straight line and a portion of an elliptic curve. The straight line is drawn from the intersection of the maximum size of coarse aggregate line, with the 100 per cent line tangent to the elliptical curve. The abscissae of this point of tangency is PROPORTIONING, MIXING, AND PLACING CONCRETE 31 equal to one-tenth of the maximum size of the coarse aggregate, and the ordinate (or height of the tangent point) is equal to 35.7 per cent for crushed stone and sand, 33.4 per cent for gravel and sand, and 36.1 per cent for crushed stone and screenings. When a fixed proportion of cement in respect to the total aggre- gate is used, various combinations of the fine and coarse aggre- 100 = E 9 Paeamme mh... Sa a A Pee ee ay | oo) Te a ees ee eee | eee et wl) Se sae aa ee oe ee: eee eee | ey tt caine aeenmere cae iE ey Ee ee pel oe J 2 Ane eee: tts ttt ete t+ tot ¢ ll ASS a2) eee eee: i el 2 a a2 oh oS TES a ee eo a ee de ee PSSA PRS es Es a eae ioe meeeeea io te ee eee er ie) 010 H 920 030 050 060 0.70 080 0.90 1.00 Bye cece of Particle in Inches. Fic. 7.—Maximum density and combined aggregate curves. gates are tried, and the curves of the trial mixes are plotted until a mix is found, whose curve agrees fairly well with the maximum density or “‘ideal” curve. Sometimes itis necessary to screen the coarse aggregate into two or more sizes, in order to obtain the densest and best mixture. For a good working concrete, the portion of the trial curve over _ the smaller sieve diameters should not fall below the ‘ideal’ curve, as it is better to have a slight excess of fine material in the mix. In regard to the portion of the trial curve over the larger 32 CONCRETE PRACTICE sieve openings, it is immaterial whether the trial curve is a little above or a little below the ‘‘ideal”’ curve. This method of proportioning is not thought to be of great practical value in designing concrete mixes for strength, because it has been found, in many instances, that trial mixes, whose curves did not closely approach the ‘‘ideal”’ curve, often were as strong as the trial mix whose curve agreed the closest with the ‘deal’? curve. For years, however, this method appeared to have been the best method found, and, when checked by strength tests, usually gave good results. For designing impervious mixes, this method of obtaining the best proportions is very good, because the densest mix is nearly always the most water-tight mix. JOB 5. PROPORTIONING CONCRETE BY THE SURFACE AREA METHOD This method for finding the proportions for a concrete mix is based on the assumptions that the strength of concrete depends upon the amount of cement used in relation to the surface area of the aggregate, and upon the consistency of the mix. The general method of procedure for proportioning concrete by this method is as follows: 1. Make sieve analyses of the aggregates. 2. Find the average number of particles per unit weight of the ageregate passing one sieve and held on another. 3. From the results of (2), and the specific gravity of the particles, compute the average volume of each size of particle. 4. Compute the surface areas from the average volumes of the various sizes and shapes of the particles. (Grains of sand and gravel are assumed as spherical, while particles of broken stone are assumed to be one-third cubes and two-thirds parallelopipeds. ) 5. Determine the total surface area of the aggregates. 6. Base the quantity of cement on the total surface area. 7. Base the quantity of water on the quantity of cement and the total surface area of the aggregates. 8. Make strength tests on the mortar or concrete as deter- mined in (7). 9. Increase or decrease the cement and water content of the mix until a mix is found that gives the required strength. The PROPORTIONING, MIXING, AND PLACING CONCRETE 33 correct water-cement ratio must always be maintained, or else the results will not be satisfactory. The work required for this method of proportioning can be simplified in the laboratory by the use of curves and tables, showing the relations between surface areas and unit weights of particles of various shapes and sizes and specific gravities, water-cement ratios, and the relations between strength and cement content and surface areas, ete. Results of tests do not appear to prove the correctness of the assumptions made for this method of proportioning, but tend to show that the surface area and consistency of mix are only two of several factors affecting the properties of the concrete. JOB 6. PROPORTIONING CONCRETE BY THE USE OF THE TABLES IN THE 1924 REPORT OF THE JOINT COMMITTEE If instructions are carefully followed, the tables given in Appendix 6 (taken from the 1924 Report of the Joint Committee) may be used to obtain the proportions of a concrete mix which will have a required compressive strength at an age of 28 days. These tables naturally cannot take into consideration all of the different types and kinds of aggregates and, consequently, there may be some aggregates for which the tabulated proportions will not give the desired strength results. Therefore, whenever time permits, control tests should be made to check the proportions selected from the tables. When using these tables, it is assumed that good portland cement, clean mixing water, and clean and structurally sound aggregates are to be used in the concrete. The tables include possible variations in the size and grading of the aggregates, and in the consistency of the mix, as shown by the slump test. The tables in Appendix 6 are to be used: 1. To furnish a guide in the selection of mixtures to be used in preliminary investigations of the strength of concrete from given materials. 2. To indicate proportions which may be expected to produce concrete of a given strength under average conditions where control tests are not made. The method of procedure in selecting proportions from these tables is as follows: 34 CONCRETE PRACTICE 1. Decide on the unit compressive strength to be required of the mix. (This is usually stated by the designing engineer or architect. ) 2. Select the consistency of mix to be used on this particular job. (This is usually stated by the designing engineer or architect. ) 3. Obtain representative samples of the fine and coarse aggre- gates, and determine their maximum and minimum sizes by mak- ing sieve analyses, using the sieves given in the tables. Apply the rules given on the first page of Appendix 6 when determining the size of a given aggregate to be used in connection with the tables. 4, Select the required mix from the tables, interpolating for strengths, aggregate sizes, and consistencies when necessary. The proportions listed in the tables are by volumes of cement (based on 94 lb. equaling 1 cu. ft.) to volumes of fine and coarse ageregates compacted by rodding in the measuring box, as specified in the Standard Method of Test for Unit Weight of Aggregate for Concrete (Appendix 2). In laboratory work, it is advisable to find the weights per cubic foot of the aggregates (as directed in Appendix 2) and then change the proportions by volume to proportions by weight. Exercises.—Given a sand which passes a No. 4 sieve and has 16 per cent retained on a No. 8 sieve, and a crushed stone which passes a 1 %-in. sieve, has 18 per cent retained on a 1-in. sieve, has 19 per cent passing a 3¢-in. sieve, and has 4 per cent passing a No. 4 sieve. a. Select proportions for a mix to give a 28-day compressive strength of 2500 lb. per sq. in. with a consistency of mix to have a slump of 6 in. b. Select proportions for a mix to give a 28-day compressive strength of 2750 lb. per sq. in. with a consistency of mix to have a slump of 8 in. If the unit weights of the cement, sand, and crushed stone in the preceding question are 94, 110, and 100 lb. per cu. ft., respectively, compute the proportions by weight for the mixes selected for parts (a) and (0). Given a sand having 3 per cent retained on a 3-in. sieve and 22 per cent retained on a No. 4 sieve, and a gravel having 2 per cent retained on a 1 }-in. sieve, 30 per cent passing a 34-in. sieve, and 12 per cent passing a 3¢-in. sieve. a. Select proportions for a mix to give a 28-day compressive strength of 2000 Ib. per sq. in. with a slump of 8 in. b. Select proportions for a mix to give a 28-day compressive sthenieth of 3000 lb. per sq. in. with a slump of 4 in. eS a PROPORTIONING, MIXING, AND PLACING CONCRETE 35 JOB 7. PROPORTIONING CONCRETE BY THE WATER-CEMENT RATIO AND SLUMP TEST In proportioning concrete by this method, the water-cement ratio is used to determine the compressive strength of the con- crete, and the slump test to determine the workability or con- sistency. There are three rules to be observed: 1. Use the exact amount of water with each sack of cement to produce the desired compressive strength. If there is water present in the aggregates, this water must be included when determining the amount of water used for the mix. 2. Use enough mixed aggregate with the cement and water to give a concrete mix of the consistency needed for the particular work in question. This consistency should be specified by the slump in inches. | 3. If the amount of work warrants, mix the fine and coarse aggregates so that as large a proportion of mixed aggregate as is practical may be used with the cement and water, and yet have a mix of the desired consistency. In general, to avoid the possi- bility of a harsh mix, the weight of fine aggregate in the combined or mixed aggregate should not be more than the weight of the coarse aggregate, or less than half the weight of the coarse aggre- gate. In the mixed aggregate, the fine aggregate shall be that passing (finer than) a No. 4 sieve, and the coarse aggregate that retained on (coarser than) a No. 4 sieve. For work in the field or laboratory, where the proportioning of the mix is accurately controlled, the gallons of water required per sack of cement for a desired 28-day unit compressive strength may be found from Curve A (Fig. 3), on page 18, or by the formula: 27,700 Gallons of water per sack of cement = S + 1700 where S is the 28-day unit compressive strength. Sometimes the gallons of water per sack of cement found by Curve A or the above formula are reduced by 14 gal. per sack of cement to allow for slight errors in measuring the water. For practical work, where it is more difficult accurately to control the proportioning of the mix, the values recommended for 36 CONCRETE PRACTICE use are those given by Curve B, (Fig. 3), page 18, or by the formula: 24,400 S + 1700 These proportions of water to cement have been based on the results of a great many tests, and, consequently, may be expected to give the desired results in nearly every case. The tests, however, have not taken into consideration every kind and type of aggregate which may be used in concrete, and there may be some aggregates for which the values given in the tables will not apply. When there is any doubt, control tests should be made as a check on the compressive strength and other qualities of the mix. For field work, 1 U.S. gal. of water may be considered as 231 cu. in., or 8.35 lb. One cu. ft. of water weighs 62.35 lb., and contains about 7.5 (7.48) U.S. gallons. The amount of water or moisture contained in the aggregates must be found and considered when determining the number of gallons of water required per sack of cement. The aggregates should be stored and handled on the job, so that the moisture content of the aggregates will not be subject to frequent or unnecessary changes as they come to the mixer. ‘The amount of moisture in an aggregate is rarely less than 2 per cent by weight, is usually between 3 and 4 per cent, and often is as much as 6 or 8 per cent directly after a rain. The absorption of various aggregates, expressed as a percentage of their dry weight, will average 1.0 per cent for average sand, 1.0 per cent for gravel and crushed limestone, 0.5 per cent for trap rock and granite, from 5 to 10 per cent for porous sandstone, and up to 25 per cent for very light and porous aggregate. The amount of moisture contained in an aggregate may be found by first weighing and drying a 10- or 20-lb. sample to a constant weight, and then weighing again. The difference between the two weights gives the amount of moisture contained in the sample. The percentage of moisture should preferably be expressed in terms of the dry weight of the aggregate. The consistency of the mix should be determined by the slump test (Appendix 7). The following maximum values of the slump in inches should not be exceeded: Gallons of water per sack of cement = PROPORTIONING, MIXING, AND PLACING CONCRETE 37 sa a a a Maximum Kind of concrete slump, inches Ste ie cc rr Plain concrete: Mass concrete (foundations, basement walls, thick floors, eM ee) oe ak ee ea Sh Oe ee been. 3 Comparatively thin sections (basement floors)............ 6 Hand-finished roads and pavements..................... 3 Machine-finished roads and pavements....... - 1 teen eee? STII ast yes ce be ds ve ca cabs eusce. 2 Reinforced concrete: Columns and thin, vertical sections (thin walls and parti- Gata ike Sie gc Sie cgcecea ee cawa’ 6 Heavy vertical and horizontal sections (thick walls, thick eM OE Se aa wie wie Sed wns Ghled eb oodh ame os 3 Thin, confined, horizontal sections.....................5. 8 Muusoors and shallow beams...........0 6.06.0. eee ee 6 For an illustration of this method of proportioning, suppose that it is desired to find the proportions of cement, water, and mixed aggregate for a concrete mix to have a 28-day compressive strength of 2000 lb. per sq. in., and a slump of 6 in. From Curve A (Fig. 3) page 18, it is seen that 7.5 gal. of water per sack of cement are needed. Deducting 0.25 gal. per sack of cement for possible errors in mixing, the amount of water to be used on the job will be 7.50 — 0.25 or 7.25 gal. per sack of cement. Assume that a suitable mixed aggregate (maximum size 114 in.), as mixed on the job, contains 2 parts of fine aggregate to 3 parts of coarse aggregate by volume, and weighs 115 lb. per cu. ft. Also assume that under average working conditions, the average moisture content of the mixed aggregate is 3.0 per cent, and the absorption is 1.0 per cent. Then the net moisture available for use in the mix is 3.0 — 1.0 or 2 per cent of the dry weight of the aggregate. The dry weight of the mixed aggregate. will be 115 — 115 X 0.03 = 111.5 lb. per cu. ft. A 1:4 mix will be tried. The amount of water in the mixed aggregate will be 4 X 111.5 X 0.02 = 8.92 lb., or 1.1 gal. Suppose that the 1:4 mix by volume with 7.25 — 1.1 or 6.15 gal. of water per sack of cement is tested for slump, and that the slump is found to be 7 in., indicating that more aggregate can be used. Assume, then, a 1:4.5 mix. The amount of water to be added will be ' 4.5 X 111.5 X 0.02 025 — ( 3.35 Suppose that this mix gives aslump of 6}4 in. and is satisfactory. = 6.05 gal. of water per sack of cement. 38 CONCRETE PRACTICE The field proportions of the mix will be: 1 sack of cement to 6 gal. of water to 4.5 cu. ft. of mixed aggregates, mixed in the proportions of 2 parts of fine aggregate to 3 parts of coarse aggregate by volume. ‘This field mix may be reasonably expected to give a concrete with a 28-day unit compres- sive strength of 2000 lb. per sq. in., and at the same time permit an excess of 0.25 gal. of water per sack of cement in any one batch. Exercises.—State the three rules or principles governing the proportioning of concrete by the above method. JOB 8. PROPORTIONING CONCRETE BY THE WATER-CEMENT RATIO, SLUMP, AND FINENESS MODULUS OF AGGREGATE This method of concrete proportioning is based on fairly definite relations between the strength and water-cement ratio, and between the consistency (workability of the mix as measured by the slump test) and the grading of the aggregates as denoted by the fineness modulus. The compressive strength is deter- mined by the water-cement ratio, the workability or consistency by the slump, and the economy by the grading of the aggregate as evidenced by the sieve analysis and fineness modulus. The fineness modulus, a term used to denote the effective grad- - Ing of the aggregate, is equal to one-one hundredth of the sum of the percentages of the aggregate retained on (coarser than) the following square mesh sieves: Nos. 100, 50, 30, 16, 8, 4, and 3 in., 34 in., and 114 in. Each sieve has a clear opening just double that of the preceding sieve. The sieve openings and the method of making the sieve analysis should conform to the specifications of Appendix 38. The coarser the aggregate, the higher the fineness modulus. Tests have shown that mixtures of fine and coarse aggregates, having the same fineness modulus and the same amounts of cement and water, produced concretes of equal workability or consistency and of equal strength, provided the concrete mix was plastic, and that the aggregates were not too coarse for the amount of cement used. The tests also showed that, for any given mix of cement and aggregate, as the coarseness of the aggregate (fineness modulus) increased, the amount of water required for a given workability decreased. In other words, larger quantities of coarser aggregates may be mixed with a given amount of cement and water, and yet have a mix of the same workability or slump. There is a limit, however, to the maximum fineness modulus (or coarseness of aggregate) which may be used for any given mix, PROPORTIONING, MIXING, AND PLACING CONCRETE 39 as an aggregate which contains too many coarser particles will cause the mix to be harsh and to deviate from the strength rela- tion given by the water-cement ratio. The following table gives the approximate maximum permissible values of fineness modulus for aggregates of varying sizes and for different mixes: Maximum Practica VALUES OF FINENESS Mopu.us Volumetric ratio of cement to aggregate = real mix poet 1:1 ja | 1:3 | 1:4 | 1:5 | 1:6 | 1:7 | 1:9 aggregate Maximum values of fineness modulus Mortars: Oy 16 Sena ee TOL 200.0) 42.00+) 2515. 12.05.) .1.95° 1.85 aT ces as Seu oes o 3 10.) 2.90 | 2.75 12.66 | 2,55) 2.45 (ne Be 4.75 | 4.20 | 8.90 | 3.60 | 3.45 | 3.30 | 3.20 | 3.05 Concretes: O-— 3...... Deer Oo ) 4-70 | 4.404) 4.201) 4205-|.3:95 | 3.385 PO owas ihGO,0n (5245 |:5,10 | 4:80 |) 4.60 | 4.45 |-4:35 | 4.25 eo 7 GepOneo.o0) 5.50 (95:20, ).5.00 1.4.85 |} 4:75°) 4.65 oe tS eet eee eee Seu ou | 0:90) 5.60 | 5.40 | 5.25 115.15 |. 5.00 O-1\%....... peooe asi) | 6.30 1 6.00 1 5.80 | 5/65.) 6:55 | 5.40 oy AE eee aoe 0 16-70 | 6340) 6220 1 6.05 |-5.95 |.5.:80 Os Smee, Sevusereoo | {elo 6.85 |-6760 + 6.50 | 6.40 | 6.25 ly, Half sieves not used in computing fineness modulus. For mizes other than those given in the table, use the values for the next leaner mix. For maximum sizes of aggregate other than those given in the table, use the values for the next smaller size, This table is based on the requirements of sand and gravel aggregate in ordinary uses of concrete in reinforced concrete structures. The values given in the table should be reduced by 0.25 for crushed stone, slag, or screenings, and also for concrete work of comparatively thin sections. For concrete work, the practical limits of the fineness modulus for fine aggregates are from 2 to 4; for coarse aggregates, from 5.50 to 8; and for mixed aggregates, from 4 to 7, depending upon the maximum size of the aggregate in question and the propor- tions and consistency of the mix. Fig. 4, on page 20, shows the relation in graphical form. 40 CONCRETE PRACTICE The size of an aggregate may be determined by the following rules: 1. Use ihe sieves listed in Appendix 3. 2. Not less than 15 per cent of an aggregate shall be retained on the sieve next smaller than that considered as the maximum size. The minimum size of a fine aggregate is usually considered as 0. 3. Not more than 15 per cent of a coarse aggregate shall be finer than the sieve considered as the minimum size (but more than 15 per cent shall be finer than the sieve which is next larger than that considered as the minimum size). The proportions of a real mix are by volume of cement (1 sack of 94 lb. assumed as 1 cu. ft.) to volume of dry, rodded, mixed aggregate. The proportions of a field mix are by volume of cement to volumes of aggregates as found and measured in the field. Consequently, the proportions of the two mixes may differ considerably. When the fineness moduli for the fine and coarse aggregates are known, the proportions in which to combine these aggregates to give a mixed aggregate having a desired fineness modulus (less than that of the coarse aggregate) may be found by the formula: Me —™M ‘=e Me — Mf where m, m-, and my are the fineness moduli of the mixed, coarse, and fine aggregates, respectively. 7; is the ratio of volume of fine aggregate to the sum of the volumes of fine and coarse aggregates measured separately. : 3 In a 1:3:5 mix, i, = 3 ak 0.375. This formula may be used to find the fineness modulus of the mixed aggregate when the proportions and fineness moduli of the fine and coarse aggregates are known. For convenience, the formula should be expressed in the following form: 3 m = rsmMms +- ¢ oe rs)Me Note that (1 — ry) is the ratio of the volume of the coarse aggregate to the sum of the volumes of the fine and coarse aggregates measured separately. ; | PROPORTIONING, MIXING, AND PLACING CONCRETE 41 When fine and coarse aggregates are mixed together in certain definite volumetric proportions, the volume of the mixed aggre- gate will be less than the sum of the volumes of the fine and the coarse aggregates measured separately, because a large part of the fine aggregate will tend to fill the spaces or voids in the coarse aggregate. The ratio of the volume of the mixed aggregate to the sum of the volumes of the fine and the coarse aggregates is given by the following formula: rywr + (1 — ry). "a _ m where wy, W., and wm are the unit weights of the dry fine, coarse, and mixed aggregates, respectively. ?m 18 the ratio of the volume of dry mixed aggregate to the sum of the volumes of the dry fine and dry coarse aggregates measured separately. | r; 1s the same as before. This ratio, 7m, 1s sometimes called the shrinkage factor, and is used in computing the proportions of the fine and the coarse aggregates in the real mix. The following method of procedure is suggested for finding the correct proportions, by this method, for a concrete mix to have a given compressive strength and slump. 1. Secure representative samples of the aggregates and make any preliminary tests necessary to determine their cleanliness and quality, such as tests for silt and organic impurities. 2. Determine the moisture content of the aggregates. 3. Make sieve analyses of the aggregates and determine their fineness moduli and limiting sizes. 4. Knowing the required strength and slump, determine the real mix and the fineness modulus of the mixed aggregate for this mix from the curves of Fig. 4, page 20. 5. Compute the ratios of volumes of fine and coarse aggregates to give the required fineness modulus of the mixed aggregate in the real mix. 6. Find the unit weights of the fine and coarse aggregates as they will be used in the field. 7. Find the unit weights of the dry fine and the coarse aggre- gates according to the method of Appendix 2. 42 CONCRETE PRACTICE 8. Mix the dry fine and dry coarse aggregates in the propor- tions found-in Rule 5 above, and find the unit weight of the dry mixed aggregate according to the method of Appendix 2. 9. Compute the ratio of the volume of dry mixed aggregate to the sum of the separate volumes of the dry fine and dry coarse aggregates. 10. Compute the volumetric proportions of the cement, dry fine aggregate, and the dry coarse aggregate in the real mix. 11. Determine the volumetric proportions of the field mix. 12. Determine the amount of water required per sack of cement from the proper curve of Fig. 3, page 18, and compute the net amount of water per sack of cement to be added to the field mix. 13. Mix a small batch of concrete in the required proportions for the field mix and determine the slump. If the slump found does not agree with that assumed, the mix must be repropor- tioned. To increase the slump a little, decrease the proportions of the aggregates slightly (say from 3 to 5 per cent), and vice versa. 14. Observe if the batch made for the slump test is too harsh or not for the work in question. If the concrete is too harsh, the mix must be reproportioned using a lesser fineness modulus for the mixed aggregate. 15. If time permits, make and test some cylinders made from a field mix as a check on the strength. Note that in the above procedure the strength of the concrete, and the gallons of water required per sack of cement, are based on Curve B of Fig. 3, page 18. If conditions in the field are such that Curve A of Fig. 3 may be used, the same procedure of deter- mining the proportions of the mix applies, if the following pre- liminary rule is observed: “Find the corresponding strength on Curve B for the same water-cement ratio, and then design the mix for this strength using the curves of Fig. 4.” : For example, the required proportions of a mix, to give a compressive strength of 2500 lb. per sq. in. under Curve A condi- tions, would be the same as the proportions needed to give a strength of 2000 lb. per sq. in. under Curve B conditions, PROPORTIONING, MIXING, AND PLACING CONCRETE 483 Ezxercises.—If the size of the mixed sand and crushed stone aggregate in a concrete mix is 0:1} in., about what would be the maximum permissible value of the fineness modulus for a 1:4.4 real mix? What is the ratio of the volume of fine aggregate to the sum of the volumes of the fine and coarse aggregates measured separately, when the fineness moduli of the mixed, fine, and coarse aggregates are 5.20, 3.10, and 6.45, respectively? What would be the fineness modulus of a mixed aggregate containing 40 per cent of fine aggregate, if the fineness moduli of the fine and coarse aggregates are 2.95 and 6.70, respectively? If a mixed aggregate contains 43 per cent of fine aggregate and the unit dry weights of the fine, coarse, and mixed aggregates are 107, 98, and 121 lb. per cu. ft., respectively, what would be the shrinkage factor or ratio of the vol- ume of the dry mixed aggregate to the sum of the volumes of the dry fine and dry coarse aggregates measured separately? __ If field conditions were such that the compressive strength of the concrete could be based on Curve A of Fig. 3, page 18, and the mix was to be designed for a compressive strength of 3000 lb. per sq. in., what strength value should be selected if the curves of Fig. 4 are to be used when designing the mix? JOB 9. ILLUSTRATIVE EXAMPLE OF PROPORTIONING CONCRETE BY THE WATER-CEMENT RATIO, SLUMP, AND FINENESS MODULUS OF THE AGGREGATE It was desired to proportion a concrete field mix to have a slump of about 7 in., and to give a 28-day compressive strength of 2000 lb. per sq. in. The job was comparatively large and field conditions were such that the proportioning of the aggregates could be (and were) accurately controlled, so that the use of Curve A of Fig. 3, page 18, was justified for determining the relation between the strength and water-cement ratio. ~The method of procedure given in Job 8 was followed. Corresponding strength of mix from Curve B of Fig. 3 was - found to be 1550 lb. per sq. in. 1. Representative samples of the fine and coarse aggregates were secured, and the aggregates tested and found satisfactory in regard to silt and organic matter. 2. The moisture was determined and found to be 3.5 per cent for the sand, and 2 per cent for the crushed limestone by weight. The percentage of absorption was assumed as 1 per cent for both sand and crushed limestone. 3. Sieve analyses of the dry aggregates were made, and the following results obtained; 44 CONCRETE PRACTICE RESULTS OF SIEVE ANALYSES Sieves Aggregate 100 | 50 | 30 | 16 | 8 | 4 34 | 134 Percentages coarser than each sieve SAT) eet Gs te eat oe te oy 97.\ ‘78 |. 57). 380i eisteeo 0 0 0 SEONG Ate Soy Tae oe is 100 | 100 | 100 | 100 | 100 | 97 | 68 | 82 3 Fineness modulus of sand = 2.80, size Oto 4. 3 Fineness modulus of stone = 7, size 4 to 14. 4. From the curves of Fig. 4, page 20, a slump of 7 in., a Curve B strength of 1550 lb. per sq. in., and a maximum size of aggregate of 14% in., gave a real mix of 1:5.5 with a fineness modulus of 5.65. 5. Ratio of volume of fine aggregate to sum of volumes of fine and coarse aggregates measured separately was found to be: Me = «1 oD, 00 gee tT ney 1 2 80 Similar ratio for coarse aggregate = 1—0.32 = 0.68. 6. The unit weights of the aggregates as measured in the field were found to be: = 0.32 Sand, damp and loose = 91.5 Ib, per eueae 91.5 lb. damp, loose sand = 88.3 lb. when dry Stone damp and loose = 98 lb. per cu. ft. 98 lb. damp, loose stone = 96 lb. when dry 7. The unit weight of the dry, rodded aggregates were: Sand = 109 lb. per cu. ft. Stone = 103 lb. per cu. ft. 8. The unit weight of the dry rodded mixed aggregate, in the proportion of 32 per cent sand and 68 per cent stone, was 121 lb. per cu. ft. 9. Ratio of volume of dry, mixed aggregate to sum of separate volumes of dry fine and dry coarse aggregates was: pp ES + (1 ry) we 0.32 X% 108 0 be ae ae Wm ve 121 foes) md OU ee O aro Searcy pom mr ik (shrinkage factor) PROPORTIONING, MIXING, AND PLACING CONCRETE 45 10. Volumetric proportions of cement and dry fine and dry coarse aggregates in real mix of 1:5.5 were: fee 5.5 X 0.382 5.5 X 0.68 mes00. ©. 0.865 11. Volumetric proportions of the field mix were: 109 X 2.03 103 X 4.32 a ess.a! 96 say a 1:2.50:4.65 mix. 12. Net amount of water, per sack of cement, to be added to the mix was found as follows: This net amount of water equals the amount required for strength (water-cement ratio) minus the amount in the aggregate plus the amount absorbed by the aggregate. Amount required for strength = 7.5 gal. per sack of cement. Amount contained in aggregates = 1:2.03:4.32 = 1:2.51:4.64 = amount in sand plus amount in stone = 2.50 X 88.3 X 0.035 + 4.65 X 96 X 0.02. = 7.73 + 8.93 = 16.66 lb. = 2 gal. per sack of cement. Amount absorbed by aggregates = amount absorbed by sand plus amount absorbed by stone = 2.50 X 88.3 X 0.01 + 4.65 X 96 X 0.01 = 2.21 + 4.47 = 6.68 lb. = 0.80 gal. per sack of cement. Net quantity of water to be added to mix = 7.50 — 2 + 8.80 = 6.30 gal. per sack of cement. 13. A small batch of concrete in the given proportions was mixed and, when tested, gave a slump of 714 in., which was satisfactory. 14. The mix did not appear to be too harsh for the work in question. 15. Strength tests were made, which gave a unit compressive strength of 1085 lb. per sq. in. at an age of 7 days. The time did not permit the making of the 28-day strength tests. The proportioning of the mix was considered as satisfactory. Exercises.—Using the same aggregates and making similar assumptions, design a concrete mix to have a slump of from 3 to 4 in., and to give a 46 CONCRETE PRACTICE 28-day compressive strength of 2000 lb. per sq. in. Assume that the working conditions in the field may not be very good so that Curve B of Fig. 3 applies. JOB 10. CONSISTENCY OF CONCRETE The consistency of the concrete should be such that the mix will be plastic and workable. The concrete should work readily into the corners and angles of the forms and around the reinforce- ment without excessive rodding, tamping, or spading. For 4 % i : Proper consistency for rrass CONCTEPE, 90 & yA ANN asertrn Lighwa Daremenee ere Ha YTS Xh\ Sy VFM OY 80 SN : \\_ tb 7is range of consistency should OTS iy \| 4¢ used for cast products remrorce: DB 1 y coricrere, erc;thin (ernmlers regiuive 70|> ‘ the greater arri0urr of wares [4 TR a eae With this consistency abour < : ipa the strenari? lost ti Nee Ll | Se Ba ea ThI$ COrSISTEn. made corncrere ow With thesloppy’concrere sore = times used i Toad work and 177 building constructor, two-thirds to three-fourths of the possible strength of the concrete 15 lost: Percent of Maxirnum Stren. 70 80 90 100 10 120 130 140 150 [60 170 180 190 0 Water Used- Figures are percent of Quantity Giving Maximum Strength. Fia. 8.— Effect of quantity of mixing water on strength of concrete. (Abrams.) different kinds of work, different consistencies will be needed. A comparatively dry mix would be suitable for heavy foundations, while a much wetter mix would be needed for reinforced concrete columns and thin wall partitions. The mix should not be so wet that free water will collect on the surface. The rule in the field should be to use as little water as possible and yet have a workable concrete mix. A comparatively slight increase in the amount of water will invariably cause a decided decrease in the compressive strength of the concrete. On some jobs where very wet mixes are used, the resulting compressive strength of the concrete may not be more than 50 per cent of PROPORTIONING, MIXING, AND PLACING CONCRETE 47 what it would have been if the amount of mixing water had been restricted to the minimum amount needed for workability. Professor Abrams has shown conclusively the effect of varying the amount of mixing water in a concrete mix with the propor- tions of cement and aggregate remaining the same. ‘The results of his investigations are shown in a graphical form in Fig. 8. The ‘‘slump test”’ is recommended by the Joint Committee in their 1924 Report for measuring the consistency or flowability of a concrete mix (see Appendix 7). In this test, the tendency of the concrete to ‘‘slump,” or reduce its height due to gravity action, is measured. ‘The original height of the molded specimen (12 in.), minus the height (in inches) after subsidence, gives the slump in inches. An increase in the amount of mixing water will increase the slump, and vice versa. If a certain quantity of water is required for a consistency giving a slump of 14 to 1 in., an addi- tion of 10 per cent more water will give a slump of 8 to 4 in., 25 per cent of 6 to 7 in., and 50 per cent of about 10 in. The following specifications for consistency are taken practi- cally verbatim from the 1924 Report of the Joint Committee: The quantity of water used shall be the minimum necessary to produce concrete of a workability required by the engineer. The consistency of the concrete shall be measured by the slump test described in the Tenta- tive Method of Test for Consistency of Portland Cement Concrete (Serial Designation—D138-25T) of the American Society for Testing Materials (Appendix 7). The slump for the different types of concrete shall not be greater than those authorized by the table which follows, unless authorized by the engineer. The consistency shall be checked from time to time during the progress of the work. WoRKABILITY OF CONCRETE Maximum Type of concrete Sa aie: Ul centre Se a ee 3 Reinforced concrete: a. Thin, vertical sections and columns............... 6 RISD CSS TSS ie ee c. Thin, confined horizontal sections................. 8 Roads and pavements: Fo eta Ye CLCYORTN O's SS RS ir 3 PRIME STREP IVIOUICULS 55% 2 -9> ops ose cas anne ae os 8 ae 1 eerie MIO OT INIA: © sii o ace bee wine ooo oo aes wee eee et 2 48 CONCRETE PRACTICE Exercises—Why should a wetter mix be used for thin concrete sections as reinforced concrete columns than for heavy concrete sections as massive foundations? Briefly describe the method used in the slump test to determine the consistency of a mix of concrete. JOB 11. MEASURING CONCRETE MATERIALS There are two ways of measuring concrete materials in use at the present time: by volume, and by weight. The common way of measuring concrete materials by volume is to measure the cement by the sack (assuming that one sack of 94 lb. of cement equals | cu. ft.), and the fine and coarse aggregates loose, as they are thrown into the wheelbarrows or hopper of the mixer. Usually no correction is made for the water content of the aggregate, or the bulking effect of water in the fine aggregate. ‘The consistency of the mix is left to the judgment of the mixer operator. Batches made by this method will usually vary greatly as to their volu- metric proportions and consistency. If the aggregates are dry and are carefully measured in measur- ing boxes or hoppers, the proportioning will be more satisfactory. When the fine aggregate (sand) contains some moisture, the bulk- ing effect of this moisture in the sand must be allowed for. If allowance is not made, this bulking effect may cause an error as large as 25 or 30 per cent, when measuring the sand. A variation of 2 per cent, for example, in the moisture content, may cause a variation of about 10 per cent in the volume of the sand. It is very difficult to correct for this bulking effect, when the sand comes to the mixer with a varying moisture content. The consistency of the mix may be controlled by slump tests made on the job. The water tank of the mixer should be so devised that the correct amount of water may be added to each batch. An automatic attachment (which can be set and locked) on the water tank of a mixer of large capacity is essential. The best way of measuring concrete materials by volume in the field is to measure cement by the sack, the coarse aggregate loose, by the use of a measuring box or hopper, and the fine aggregate and water together, by the inundation method. It has been shown by tests that the bulking effect of water in fine aggregate is practically negligible, or very small, when the fine aggregate is 4 : : PROPORTIONING, MIXING, AND PLACING CONCRETE 49 completely inundated by water. Therefore, if the volume of the fine aggregate is measured when it is covered by water, very uni- form results will be obtained. After the correct amount of water has been determined for any mix, this water may be placed in a water-tight hopper and the fine aggregate then added. Concrete materials may be measured very easily and accurately by weight by using hoppers with automatic scales. A correction must be made for the water content of the aggregates, not so much for the effect in the quantity of aggregates used as for the effect of this water content in the water-cement ratio of the batch. The water content of a batch should never vary more than }4 gal. (about 2 lb.) per sack of cement in any particular batch. All methods of measuring concrete materials have their advan- tages and disadvantages, when used on the job, and no method yet discovered is ‘‘foolproof.”’ Probably the methods of measur- ing the concrete materials by weight and by volume, with the sand inundated, are the two best methods yet devised for large jobs, especially when the consistency is checked rather frequently by the slump test. The moisture contained in the aggregates is the most troublesome factor in the correct measurement of con- crete materials. Exercises—Name some advantages and disadvantages of measuring concrete materials by: 1. Volume with cement by the sack, fine and coarse aggregates loose in barrows or hoppers, and water in a tank on the mixer. 2. Volume with cement by the sack, coarse aggregate in a measuring box or hopper, and water and fine aggregate together with fine aggregate inundated. 3. Weight with cement by the sack or pound, and with the fine and coarse aggregates and water in hoppers having automatic scales. Given, concrete materials with the following unit weights: cement, 94 Ib. per cu. ft., sand, 108 lb. per cu. ft., and crushed stone, 97 lb. per cu. ft.: (1) Find the proportions by weight of a 1:2:4 mix by volume; and (2) find the proportions by volume of a 1:2:4 mix by weight. JOB12. COMPUTING QUANTITIES OF MATERIALS FOR CONCRETE The present specifications (1924 Report of the Joint Committee) state that the unit of measurement for concrete mixes shall be 1 cu. ft., and that 94 Ib. of cement (one sack or bag or 14 bbl.) shall be considered as 1 cu. ft. 50 CONCRETE PRACTICE The following approximate rule may be used in computing the quantities of materials required for 1 cu. yd. of concrete. The proportion of cement, c, is taken as unity. Sacks of cement per cubic yard of concrete 42 ae c+st+q Cubic yards of fine aggregate per cubic yard of concrete aly os ee CTs 24 Cubic yards of coarse aggregate per cubic yard of concrete Ey Te lbo.xX 9 0X9 e+s-+g Pa When c, s, and g are the proportions by volume of cement, fine aggregate, and coarse aggregate, respectively. If the proportions by volume are for cement and mixed (com- bined) aggregate, take the volume of the mixed aggregate equal to the volume of the concrete, and base the volume of cement on the volume of the mixed aggregate; that is, in a 1:6 mix by volume of cement to mixed aggregate, 1 cu. yd. of mixed aggre- gate and 27 or 4.5 sacks of cement will be required for 1 cu. yd. of concrete. This rule will give slightly excessive quantities on large jobs, because of the bulking effect of cement and water when they are added to the mixed aggregate. In volumetric proportioning, the amount of water is usually given as gallons of water per sack of cement. The water may be measured in a tank calibrated to read to the nearest tenth or quarter of a gallon. Sometimes the water tank is graduated to read in cubic feet. A U.S. gallon of water contains 231 cu. in., and there are approximately 7.5 gal. per cu. ft. The computations required, when proportioning concrete materials by weight, are quite easy and simple. For example, in a 1:3:6 mix by weight, there would be 1 Ib. of cement for every 3 lb. of fine aggregate and every 6 lb. of coarse aggregate. In order to change cubic feet of concrete to pounds of concrete, multiply the number of cubic feet by 145 (the approximate weight per cubic foot of good concrete). The rule which follows may be used when computing weights of material per cubic yard of concrete (assuming a cubic yard of PROPORTIONING, MIXING, AND PLACING CONCRETE 51 concrete to weigh 40001b.). The proportion of cement, c’, is taken as unity, and c’, s’, and g’ are the proportions by weight of cement, fine aggregate, and coarse aggregate, respectively. Sacks of cement per cubic yard of concrete =e 42.5 et Tons of fine aggregate per cubic yard of concrete Bui oe 2s’ en eS. fete g «§©=©6 621.25 Tons of coarse aggregate per cu. yd. of concrete 29’ = ct x q’ e+e’ +a’ 21.25 To reduce sacks of cement to pounds, multiply by 94. The water is usually weighed when proportioning by weight, and the amount of water may be given as pounds of water per pound of cement or pounds of water per sack of cement. One U.S. gallon of water may be considered as weighing 8.35 lb. =G! = Exercises—Compute quantities of water (gallons), cement (sacks), sand (cubic yards), and gravel (cubic yards) for a job requiring 173 cu. yd. of concrete of a 1:1.9:3.3 mix by volume with a water-cement ratio of 1.10. Compute quantities of water (pounds), cement (sacks), sand (tons), and stone (tons), for a job containing 124 cu. yd. of concrete of a 1:2.7:4 mix by weight with a water-cement ratio of 1.20. JOB 13. HAND MIXING OF CONCRETE The mixing of concrete by hand will give good results, if care- fully and thoroughly done. This method of mixing is not economical except for very small jobs, where only a few batches are needed. The batches in hand mixing should be small, prefer- ably less than 1 cu. yd., and of such size that all the concrete in any one batch can be placed in less than 14 hr. (before initial set occurs). The tools used in hand mixing are a water-tight metal or wooden platform, two shovels, measuring boxes for materials, and pails for measuring water. If the batch is small and only one man is available for mixing, an ordinary mortar box and a hoe can be used in place of the platform and shovels. The mixing plat- form should be about 7 X 12 ft. or larger in size, and should be 52 CONCRETE PRACTICE made of tongued and grooved plank, 2 in. thick, tightly and securely nailed on 2- X 4-in. joists spaced about 2 or 3 ft. apart. The platform should have a 2- X 2-in. strip nailed around the (a) Measuring box of one cubic foot (b) Measuring box of four cubic feet capacity. capacity. Inside dimensions are: length, 36 in.; width, 16 in.; and height, 12 in: Fic. 9.—Measuring boxes. The measuring boxes have neither top nor bottom, and may easily be made of one-inch planed lumber. Fic. 10.—Convenient portable mixing platform. The platform should be made of 2-inch planks planed on one side, preferably of tongue-and-grooved material. The finished platform should be watertight and kept as nearly level as possible while mixing, to prevent the loss of water, which would carry off cement from the mixture. The platform should be equipped with skids or run- ners, so that it may be easily dragged to any desired location. alse) © 6b 6 6 és ¢ © 6 © ©) 0's 0 6 wie & 6 6 9 0 6.0 0 es Sw fe os eee Oe he me 8 wh ete 6 ae 6 [Miter stata ate eis Sitaels & ela 6s se « fo 6s 16 6-0 6 © 0 6 0 <'s © cle ee Ce oe 0 8 6 68 eo 8 ws 6 0, 6 eo jo OR 8b Gg 6 68 & 6 6 0 0 6 8 eee ee oe WHEREOF., The parties hereto have set their hands the date herein named. PATIDEON CG see tener eee ecls evils: seed , 192 5p Tae Paarl aaley 5 bil ae Meare or Nr me Re , County. Party of the First Part aes County Highway Commissioner i : y ee oT int sok 7 yt cea a Cin apa ae ge Soe ee eee ae. Ape oe eer dapat. ee Gad Fas ages eRe ae ee PN ER PO Ee 4 Sins Engineer """""" County Highway Committee I es a , 192.., for the ME TET eh oe Tk a ee WISCONSIN HIGHWAY COMMISSION Sn ea Party of the Second Part = By Pon A Behe Oe Caethlitese 3G CURSO Sysco ses (GNie OCIS ANC pCERC ORC Ta SUI St Te Jae Se ie ine VU A ea a a a} State Highway Engineer (Give Title or Position) 120 CONCRETE PRACTICE CONTRACTOR’S BOND eevee ere ene eee rece ee Hho PDO eR eC Oe wee eo oe RAIL 6 5 6 6 6 1t 6 0 0 we 6 8 0 6b 6 ©) 6) 9) © ©) miele Opler) 6) 66) et Sse) ene Noe MRI rete Oe as Suret. areheld and: firmly bound Unto)cssei ene County, Wisconsin, in the penal BUDA, OF ois econ. Soc Syapie @ © 88 kis ae Sie een ea See te ep ois Gerdes eer Dollars ($......), lawful money of the United States, to be paid to said County, for which sum of money, well and truly to be paid, we bind ourselves, our heirs successors, executors, and administrators, jointly oe severally, firmly by these presents. Sealed with our seals and dated this........ day , 192. The condition of this obligation is such, that vf the said bounden principal shall, in all things, well and truly perform all the terms and conditions of the within and foregoing con- tract COMED Vae eee performed, and within the time therein mentioned, and shall pay to each and every person or party entitled thereto all the claims for work or labor performed or materials furnished for or in or about or under such contract as provided in Section 289.16 of the Statutes, and shall have paid and discharged all liabilities for injuries which have been incurred in the said construction, under the operation of Sections102.01 to 102.34 of the Statutes, inclusive, and all acts amendatory thereto, then this obligation is void; otherwise it shall be and remain in full force and virtue. STATE OF WISCONSIN, om oe eee) 6 6 ow le 6 sible) © Ok ew) (elle alia Bae ee Ce 2 2 County Ol Acai asic bee en nner take ies eae Principal ESSA rece OAL te Raa eed ke PI es hesrgat fn og eT iS) er A ae Ae te se notes being first duly sworn, on oathsays that heis worth. thesum of ...560605. 65 68 Weve coves or 0d Allah | © ieee Daye ss. Jo bau re eae) ee Surety Dollars in property within this state, over and above all debts, liabilities and exemp- tions. BY. ooo accia ts avs sabe ee ee ee Subscribed and sworn to beforemethis:.,. 0 9 © 2.22... serene Ody Olwcaenic ome ee eee, en eee , 192 In Presence: of, .10: 2 'ss.bus eee eee ee 218 ele @ (0 (e188 6 "0 © © 50 (ev wc. 0 © Sis 6 + mm Notary Public. STATE OF WISCONSIN, Countyi0fse eo ee Le. eee Cee being first duly sworn, on oath says that he is. wortl (hersum Olsss. 6 eee eerie Dollars in property within this state, over and above all debts, liabilities, and exemp- tions. Subscribed and sworn to before me this.... Coeeeer eee re sneeereececeer eee Notary Public. NOTE—When executed by personal sureties make foregoing deposition. e098 Oe we ee 8 Oe ew Bo es se) 6 oes ae @ a bl ene’ ewe 22 0 0 0 «6 8 ew im © 6 fe 19 We hw © 6 @ So lee hte ea) eee) eer ees NOTE—When executed by a Surety Company, attach to the bond certificates from the Insurance Department that Com- pany is authorized to transact business in the State, and that agent is duly licensed at the time; also a valid power of attorney of person or persons executing bond for the Company. The foregoing bond is hereby approved #0 8 0 60 6p 0. & © OOS) w Oe wees lel sw es" wi) eee el ie re rt District Attorney Exercises—What is the object of including the items B, C, D, and £ in the standard form of proposal? Prepare a form of proposal for a concrete sidewalk based on a lump sum for the job, with possible additions and deductions at certain prices per square foot. JOB 35. SPECIFICATIONS The specifications of a construction contract refer to the details of the relations and obligations of the owner, engineer, and contractor, and to the details of the work and method of construction. The first part is called the general specifications CONTRACTS, SPECIFICATIONS, AND PLANS 121 or general conditions of the contract, and the latter part is called the detailed or technical specifications. General specifications include the following subdivisions. 1. Definition. 2. Rights of owner in.regard to inspection and supervision, right of access to work, changes, alterations, extra work, dis- crepancies, omissions, etc. 3. Engineer’s or architect’s authority in regard to the work. 4. Method of making estimates and payments for regular and extra work. 5. Contractor’s responsibilities in regard to himself and workmen, compliance with laws, protection against damages and claims for labor and materials, assignments, subcontracts, time of completion, rate of progress, liquidated damages, pro- tection of work, defective work, delays, construction plants, sanitation, etc. Detailed or technical specifications include clauses specifying the kinds and quantities of the materials and the methods of doing the work. For example, technical specifications for a concrete sidewalk would include clauses in regard to the excava- tion, foundation, drainage, forms, kind and quality of the cement, sand, and stone, proportions of mix, consistency of mix, method of mixing concrete, method of placing concrete, method of finish- ing the surface, protection from weather, disposal of surplus material, and cleaning up. If not stated in another part of the contract, the length, breadth, and thickness of the walk should be given. When writing technical specifications, the first requisite is clearness. ‘The words, phrases, sentences, and paragraphs should be so selected and arranged that there can be no uncertainty as to the meaning of the specifications. The-use of ambiguous words and terms should be avoided. Specifications should be brief, but clearness should not be sacrificed for brevity. Indefinite, indeterminate, ambiguous, and arbitrary specifica- tions are to be avoided, as well as specifications which are unfair to the contractor or owner. Whenever practical, it is advisable to specify stock articles and sizes, as such are invariably cheaper than special articles 122 CONCRETE PRACTICE and sizes. Special brands preferably should not be specified, unless the bidder is given a chance to suggest other suitable brands. A specification writer should be careful not to use parts of published specifications unless he is sure that these parts apply to the work contemplated. A study of published specifications is wise, but the blind copying of parts of these specifications for other work should be avoided. In determining the requirements for certain materials, it is often satisfactory to require them to pass certain well-known standard specifications and tests. For example, the portland cement used should be such as will pass the requirements of the A. 8. T. M. Standard Specifications for Portland Cement. In regard to writing specifications for methods of doing work, it is usually more satisfactory to leave the choice of methods to the contractor and then hold him responsible for the satisfactory performance of the work. If the method is specified and the work then turns out unsatisfactorily after the contractor has followed this method, he (the contractor) may escape the respons- ibility for the poor work. When writing specifications always examine each paragraph and clause to see if it represents good practice, if it applies to the work for which it is written, and if it is consistent and agrees in general with the other paragraphs and clauses with which it is to be used. Exercises—What are general specifications? What things do they include? What are detailed specifications? What do they include? Why is it sometimes not advisable to specify methods of doing work? JOB 36. STANDARD SPECIFICATIONS FOR A REINFORCED CON- CRETE HIGHWAY BRIDGE The following specifications are general specifications for all highway bridge work, and detailed specifications for concrete in forms prepared and used by the Wisconsin Highway Commission. Note that the general specifications have, on the first page, blank spaces, which are to be filled in with the name and general description of the job in question, and with a list of the plans included in the contract. : CONTRACTS, SPECIFICATIONS, AND PLANS 123 In the detailed specifications for Concrete in Forms there are several clauses which may not be needed for certain jobs. For example, if all concrete was to be of Class A, clauses relating to Classes B, C and D would not be needed. Also, if a deck girder bridge were to be built, clauses relating to slab bridges and arches would not be required. WISCONSIN HIGHWAY COMMISSION being a part of contract annexed hereto. ihewore to be done under the contract shall be... 2... 20. cece cee ect cece ceccceveve See ere eee id see) Siew 66 6 ie 86 «a Sl 6 wet eC HHO Ae Rw KT Kee OO eK Ree CESS CCC eK BOC Cee eC Ree eH a ee ee eee Se ee Bae se sd we Se 6's 2 6 8 6 4 hw 6 eC ee CORO HCH SMO OME eee eMC HO KTH MKB ee KC MO Meee Ee CaS Siete eee eee ee eee ee SWE e) (pe (Cees — 26 eaters bis Oe ees a KO ee CU Dee ee He Ce nse Gee ea eewe res eer evnevacese ae wae ale) sé) ie) pe 6,05 1018 6 oe 6 66 6 Ce se wo Ce OCS TENS SORE CHM KS TeV EO CP e Se eraeecnsreveeve The plans mentioned in the contract are as contained in drawings prepared by the Wis- consin Highway Commission, and annexed hereto marked................00ce0eeeeeeee i ey sree eee eee ees es eee eee e eee eee eee eee sere reser eres eee eee eee eee eee eee eee eee ee eee eens Si i ee 2 GENERAL PROVISIONS 1. Work.—It is understood that the work to be done includes everything which might reasonably be considered necessary for a complete and work- manlike job in accordance with the plans and specifications in every detail. _ The Engineer will furnish and set survey stakes, or other marks at random distances from the center line of the contemplated roadway and furnish the contractor with a grade sheet showing the horizontal and vertical distances from said stakes or marks to the center of the roadway. The Contractor shall make such measurements, and set such stakes as may be necessary to begin work. He shall furnish all material, tools, machinery, labor and other means of construction to complete the work, including all excavation for foundations. He shall remove the structure existing at the site, or structure replaced by bridge mentioned in the contract, and pile the resulting material neatly on the bank. The excavations for foundations shall be according to the dimensions shown on plans and shall be carried to such depth as is necessary to secure good foundation free from all danger of damage from settlement, frost, or scour even though necessary to exceed the depth shown, but there shall be no variation in depth without a written order as herein- after provided. All excavated material and other obstructions to the stream bed at any point between the ends of the wings of the abutments shall be removed and the channel left clear and unobstructed. This includes the removal of any dirt in the banks of the stream necessary to give clear open- ing. Material suitable for back filling shall be placed in the fill back of the abutments. All foundation excavations in front of abutments and piers shall be refilled, all rubbish removed, and the bridge left in a neat condition. 124 CONCRETE PRACTICE The Contractor shall notify the Engineer a reasonable length of time (not less than five days) in advance of the time when he expects to begin work. He shall give his personal attention to the work and shall not sublet the same without the consent of the Engineer. It is understood that good appearance and proper finish shall be considered as essential to the proper execution of the work. Until acceptance of the bridge, it shall be under the charge and care of the Contractor, and he shall take every necessary precaution against injury or damage to the bridge, or to any part thereof, by the action of the elements, or from any other cause whatsoever, whether arising from the execution or from the non-execution of the work. 'The Contractor shall rebuild, repair, restore and make good at his own expense, all injuries or damages to any portion of the bridge occasioned by any cause before its completion and acceptance. 2. Time of Completion.—It is understood that the Contractor shall begin work at a reasonable length of time in advance of the time named for com- pletion, and prosecute the work with reasonable dispatch until the work is finished. If the Engineer believes that the work is unnecessarily delayed, he shall notify the Contractor and his sureties to the effect, in writing. If the Contractor, or his sureties, does not then, within ten days, take such meas- ures as will insure the satisfactory completion of the work, the Supervisors shall then have the right to order the Contractor to cease all work. The Contractor shall immediately respect such notice, stop all work, and cease to have any right on the ground. The Supervisors shall then take such means as may be necessary to complete the work. If the cost shall then be greater than the contract price, the Contractor shall pay such difference to the Supervisors, and his bond shall be security for his payment. 3. Contractor’s Liability—The Contractor shall be liable for all accidents and damages that may accrue to persons or property during the prosecution of the work, by reason of negligence or carelessness of himself, his agents, or his employees. The work shall be conducted in conformity with all state or municipal laws and ordinances applying to the work, and precautions shall be taken to guard against accidents and loss of life. Before beginning work, the Contractor shall furnish the Supervisors with satisfactory evidence that he will be able to discharge all obligations result- ing on the work, through the operation of Sections 102.01 to 102.34 of the Wisconsin Statutes through authorized liability insurance, or that he has been exempted as provided in Section 102.28. 4. Instructions to Foreman.—The foreman, or other person in charge of any particular portion of the work, shall receive and obey the instructions of the Engineer, relating to that particular part of the work, in case the Contractor is not present. Any foreman or workman employed by the Contractor on the work, who, in the opinion of the Engineer, does not perform his work in the proper manner, or who shall be disrespectful, intemperate, disorderly, or otherwise objectionable, shall at the written request of the Engineer, be forthwith discharged from the work, CONTRACTS, SPECIFICATIONS, AND PLANS 125 5. Imperfect Work.—Any work or material which shall be imperfect, insufficient, or damaged by any cause whatsoever, shall, when pointed out by the Engineer or his authorized representative, be remedied immediately and made to conform with the plans and specifications. Any omission by the Engineer, or his authorized representative, to disapprove of, or reject, any such defective work or material, shall not be construed as an acceptance of the work, or as releasing the Contractor from remedying any defective work or material so as to conform to the plans and specifications. 6. Bond.—In order to guarantee the faithful performance of the contract, and the payment of all lawful claims for labor performed and material furnished in and about the work done thereunder, the Contractor shall, before beginning work, and not later than fifteen days after the acceptance of this proposal, file a good and sufficient bond with the party of the first part, in the amount of the contract. The said bond shall be in compliance with the provisions of Section 289.16 of the Statute. 7. Maintenance of Travel.—Unless the contrary is specified, such pro- vision to maintain travel during construction, as may be deemed necessary shall be made by the party of the first part. Where the road is required to be kept open to travel by the Contractor, the same shall be maintained in a safe condition and the Contractor shall be responsible under his bond for all accidents that may occur thereon due to the unsafe condition of the road. The Contractor shall be permitted to post such signs as may be approved by the Engineer warning the public of the probable increased danger due to construction. Until the work is accepted the Contractor shall take all necessary precautions and place proper guards for the prevention of accidents, and shall between sundown and sunrise maintain suitable and sufficient lights as warning signals. . Where the road is kept closed to travel, the Contractor shall erect and maintain a suitable barrier at each end of the work, and shall post such detour signs to direct the traveling public around the work as may be directed by the Engineer. 8. Changes.—The Supervisors shall have the right to make such changes in the plans and additions thereto as may be necessary or desirable, and such changes shall not invalidate the contract. All such changes shall be ordered in writing by the Supervisors, and approved by the Engineer. Should such changes be productive of increased cost to the Contractor, a fair and equi- table sum, to be agreed upon in writing before such changed work shall have started, shall be added to the contract price, and in like manner deductions shall be made. 9. Inspector.—The Supervisors shall have the right, if they so desire, to maintain an inspector on the work, who shall have access to all its parts. Inspectors shall be authorized to inspect all work done and materials furnished. Such inspection may extend to all or any part of the work and to the preparation or manufacture of the materials to be used. An inspector may be stationed on the bridge to report to the Engineer as to the progress of the work and the manner in which it is being performed. Also to report whenever it appears that the materials furnished and the work performed 126 CONCRETE PRACTICE by the Contractor fail to fulfill the requirements of the specifications and contract, and to call the attention of the Contractor to any such failure or other infringement. Such inspection, however, shall not relieve the Con- tractor from any obligation to perform all the work strictly in accordance with the requirements of the specifications. In case of any dispute arising between the Contractor and the inspector as to materials furnished or the manner of performing the work, the inspector shall have authority to reject materials or suspend the work until the question at issue can be referred to and decided by the Engineer. The inspector shall perform such other duties as are assigned to him. He shall not be authorized to revoke, alter, enlarge or release any require- ments of these specifications, nor to approve or accept any portion of the work, nor to issue instructions contrary to the plans and specifications. The inspector shall, in no case, act as foreman or perform other duties for the Contractor, nor interfere with the management of the work by the latter. Any advice which the inspector may give the Contractor shall in nowise be construed as binding the Engineer in any way, or releasing the Contractor from fulfilling all the terms of the contract. 10. Definitions.—The terms “Contractor,” “County,” ‘Supervisors ”’ and “‘Engineer” whenever used in connection with this contract shall be under- stood to have the meanings hereinafter stated. Contractor.—The person or persons entering into this contract as party of the second part acting directly or through a duly authorized representative. County.—The governmental unit or units entering into this contract, whether it be a County, City, Village or Town. Supervisors.—The duly authorized representatives of the said govern- mental unit or units in this contract. Engineer.—The State Highway Engineer of Wisconsin or his authorized representative. 11. Referee.—It is mutually agreed by both parties to this contract that the Engineer shall act as referee in all disputes arising under the terms of the contract, between the parties thereto, and his decision shall be final and binding on both alike. 12. Estimates——When provided in the contract, the Supervisors shall make advances to the Contractor at the intervals named. The amounts shall be certified by the Engineer to the Supervisors, and shall equal the value of the work done less 15 per centum. The granting of any such estimates shall not be construed as total or partial acceptance of any part of the work. 13. Payment.—Upon the completion of the work, according to the con- tract, plans, specifications, and agreements as determined thereunder by the Engineer, the said Engineer shall make to the party of the first part a certified statement setting forth the work done by the Contractor, and the amount due him therefor. The obtaining of the certificate of the Engineer, as to the work done and the price therefor, shall be a Condition precedent to the right of the Contractor to be paid the sums due him under the terms of the contract. The Contractor shall pay all claims for work and labor performed and materials furnished in the execution of this contract provided in Section 289.16 of the Statutes. CONTRACTS, SPECIFICATIONS, AND PLANS 127 CONCRETE IN FORMS 206. Work.—It is understood that the work to be done includes everything which might reasonably be considered necessary for a complete and work- manlike job in accordance with the plans and specifications in every detail. The contractor shall perform all excavation and place concrete of the class indicated on the plans, or ordered by the engineer, for culverts, abutments, wing walls, end walls, catch basins, bridges, and other structures as directed by the engineer. All concrete placed in the work shall conform to the requirements for concrete of the class specified. All concrete and other masonry shall be built to the dimensions and contours shown on plans, with all reinforcement shown thereon. The engineer shall have the right to order the removal of any masonry not so built. The excavations for foundations shall be according to the dimensions shown on plans and shall be carried to such depth as is necessary to secure good foundation free from all danger of damage from settlement, frost or scour even though necessary to exceed the depth shown, but there shall be no variation in depth without a written order as hereinafter provided. All excavated material and other obstructions to the stream bed at any point between the ends of the wings of the abutments shall be removed and the channel left clear and unobstructed. This includes the removal of any dirt in the banks of the stream necessary to give clear opening. Material suitable for back filling shall be placed in the fill back of the abutments. All foundation excavations in front of abutments and piers shall be refilled, all rubbish removed, and the bridge left in a neat condition. 207. Material.—Concrete shall consist of approved Portland cement, fine aggregate of sand, and coarse aggregate of broken stone or gravel, mixed in the proportions specified for the various classes given below. On request samples of all these ingredients shall be submitted to and approved by the engineer. 208. Classification.—The proportions of concrete mixtures to be used in various parts of work shall be as specified on the detailed plans. The pro- portions shall be measured by volume, one sack of cement, weighing ninety- four (94) pounds net, to be considered one (1) cubic foot. In general, proportions shall be as follows: Class A.—Unless otherwise specified, Class A concrete shall contain one and one-half (114) barrels of cement per cubic yard of concrete. Proportions which will be satisfactory with well-graded aggregates are, approximately, one (1) part cement to two (2) parts fine aggregate to four (4) parts coarse aggregate. The following shall be the standard tolerances for grading of coarse aggre- gate. For the sizes two (2) inch to one-fourth (14) inch, twenty-five per cent (25%) to seventy-five per cent (75 %) of the total material shall pass a one (1) inch screen, not more than thirty per cent (30%) and not less than ten per cent (10%) of the total shall pass a one-half (14) inch screen, and not more than three per cent (3%) shall pass a one-fourth (14) inch screen. A tolerance of five per cent (5%) shall be allowed in the size of all screens. 128 CONCRETE PRACTICE Class B.—Unless otherwise specified, Class B concrete shall contain one and one-quarter (114) barrels of cement per cubic yard of concrete. Proportions which will be satisfactory with well-graded aggregates are, approximately, one (1) part cement to two and one-half (214) parts fine aggregate to five (5) parts coarse aggregate. The following shall be the standard tolerances for grading of coarse aggregate. For the sizes three and one-half (314) inch to one-fourth (14) inch, twenty-five per cent (25 %) to seventy-five per cent (75 %) of the total material shall pass a one and one-half (114) inch screen, not more than twenty-five per cent (25 %) and not less than ten per cent (10 %) of the total shall pass a one (1) inch screen, and not more than three per cent (3 %) shall pass a one-fourth (14) inch screen. A tolerance of five per cent (5%) shall be allowed in the size of all screens. Class C.—Unless otherwise specified, Class C concrete shall contain one and five hundredths (1.05) barrels of cement per cubic yard of concrete. Proportions which will be satisfactory with well-graded aggregate are, approximately, one (1) part cement to three (3) parts fine aggregate to six (6) parts coarse aggregate. The coarse aggregate shall be graded as stated under Class B. Class D.—Unless otherwise specified, Class D concrete shall contain one and six-tenths (1.6) barrels of cement per cubic yard of concrete. Propor- tions which will be satisfactory with well-graded aggregates are, approxi- mately, one (1) part cement to two (2) parts fine aggregate to three and one-half (314) parts coarse aggregate. The following shall be the standard tolerance for grading of coarse aggre- gate. For the sizes one (1) inch to one-fourth (14) inch, twenty-five per cent (25%) to seventy-five per cent (75%) of the total material shall pass a one-half (14) inch screen, and not more than three per cent (3 %) shall pass a one-fourth (14) inch screen. A tolerance of five per cent (5%) shall be allowed in the size of all screens. By order of the engineer, the proportions of fine and coarse aggregate specified in the above classification may be varied slightly in order that a dense concrete with the specified content of cement may be obtained. If the engineer shall order, in writing, proportions differing in cement content from those specified, any suitable change thus necessitated and agreed upon in advance shall be made in the contract price. If the contractor shall use cement in excess of one hundred five (105) per cent of the specified amount in any day’s run, he shall receive no pay for the excess cement, if the contractor is furnishing cement, and if the state is furnishing it, the cost of the extra cement shall be deducted from the con- tractor’s estimates. . It is further specified that the price bid per cubic yard of concrete is to exclude the cost of the cement, and that a separate and distinct bid is required on the cost per barrel of cement in place in the work. The con- tractor, when the State does not furnish cement, in making his bid on cement, shall state, in addition to his price per barrel in place, the price per barrel of cement, f. o. b. destination which he used in figuring his bid, said price to be CONTRACTS, SPECIFICATIONS, AND PLANS 129 exclusive of discounts. He shall also name the destination. In case the price per barrel of cement at said destination is more or less than the price used in the bid, due to changed price at the mill or changed railway freights, the said increase or decrease in price shall be added to or subtracted from the price bid on cement. If cement is furnished to the contractor by the Commission, said contrac- tor is not to include the price of cement (stated in the proposal) in his bid. In other words, he is to name a price per barrel for handling the cement only. 209. Portland Cement.—All Portland cement used shall meet the require- ments of the standard specifications and tests for Portland cement adopted by the American Society for Testing Materials, and known as Serial Designa- tion C 9-21, together with all subsequent amendments thereto, and also an additional specification that when the cement is mixed in the proportion of one part cement to three parts standard Ottawa sand by weight, and cured one day in moist air, and two days in water, the average tensile strength of not less than three of these briquettes shall be equal to or higher than 150 pounds per square inch. ‘The average tensile strength of standard mortar at seven days shall be higher than the strength at three days. All cement shall be properly protected against dampness and no cement shall be used which has become caked. Before the contractor shall be entitled to payment for the work, he shall present satisfactory evidence to the engineer that the full amount of cement required by the proportions specified for the work has been used. 210. Fine Aggregate.—Fine aggregate shall consist of natural sand or screenings from hard, tough, durable crushed rock or gravel, composed preferably, of quartz grains, graded from fine to coarse, with the coarse particles predominating. Fine aggregate when dry shall pass a one-quarter (14) inch round opening; between twenty-five (25) and seventy-five (75) per cent shall pass a sieve, having twenty (20) meshes per linear inch; not more than twenty-five (25) per cent shall pass a sieve having fifty (50) meshes per linear inch; and not more than five (5) per cent shall pass a sieve having one hundred (100) meshes per linear inch. Fine aggregate shall not contain organic or other deleterious matter, not more than three (3) per cent, by weight, of silt. Routine field tests may be made on the fine aggregate as delivered. In case the laboratory test shows that it contains more than three per cent (3 %) silt by weight, the entire lot of fine aggregate represented by the sample shall be rejected. The percentage of silt, by volume, in the sand, may be determined from the colorimetric test, or, more accurately, in the following manner: Select two glass bottles, jars, or graduates which have uniform bore over a depth of eight (8) inches or more. The minimum diameter should not be less than one and one-half (114) inches. Select two representative samples of the material under test, each sufficient to fill a vessel to a depth of two and one-half (214) inches. Add enough water to make the total depth of the mixture of sand 1 The twelfth paragraph under Clause 208 of “Concrete in Forms”’ shall not apply to bridge contracts. All bids for bridge work shall be a lump sum proposal as set forth in “Instructions to Bidders.”’ 130 CONCRETE PRACTICE and water five (5) inches after shaking. Cover the top with hand or cork and shake vigorously for at least thirty (30) seconds. Hold the vessel in upright position, and tap its side with the finger to level the top of the sand. Allow to stand for one (1) hour. Then read the depth of silt to the nearest one-hundredth (14909) inch, and measure the total depth of sand and silt, making four measurements at different points around the container. By dividing the depth of the silt by the total depth of sand and silt, and multi- plying by 100, the percentage of silt by volume is found. If the average percentage of silt in the two bottles exceeds six (6), make a second determi- nation of the percentage of silt after the vessel and contents have stood for six (6) hours. In case the average result obtained after the sample has stood six (6) hours is still above six (6) per cent, the engineer may reject or at his discretion send a twenty (20) pound sample of the material to the laboratory for test. The presence of organic matter in the fine aggegate may be detected by the colorimetric test, which may be made as follows: Fill a graduated, wide- mouthed nursing bottle to the four and one-half (414) ounce mark with the sand under test. Add a three (3) per cent solution of sodium hydroxide, until the level of the liquid reaches the seven (7) ounce mark after the mixture has been shaken. After thorough shaking, allow the mixture to stand eighteen (18) to twenty-four (24) hours, and observe the color of the clear, supernatant liquid. If clear or of light straw color, the sand is free from harmful proportions of organic impurities. If the color of the liquid is dark amber to black, the sand shall not be used before it has been subjected to the standard mortar strength tests. Fine aggregate shall be of such quality that a mixture composed of one (1) part Portland cement and three (3) parts of fine aggregate by weight when made into briquettes shall show an average tensile strength at seven (7) and twenty-eight (28) days equal to or greater than the average tensile strength of briquettes composed of one (1) part of the same cement and three (3) parts standard Ottawa sand by weight. The percentage of water used in making briquettes of cement and fine- aggregate shall be such as to produce a mixture of the same consistency as that of Ottawa sand briquettes of standard consistency. The word “sand,” if used on plans or elsewhere, in specifying concrete proportions, shall be understood to be the fine aggregate as herein defined. _ The right is reserved by the State to forbid the use of fine aggregate from any plant when the character of the material in such plant, or the mode of operation in such plant is such as to make improbable the furnishing of reasonably uniform fine aggregate, free from clay, silt or loam. — 211. Coarse Aggregate.—Coarse aggregate shall consist of clean, hard, tough, durable crushed rock or pebbles, having reasonably uniform gradation of material passing a screen having two (2) inch openings and retained on a screen having one-quarter (14) inch round openings. When the material is tested with laboratory screens it shall meet the following requirements: CONTRACTS, SPECIFICATIONS, AND PLANS 131 Retained on a 2-inch (round openings) screen....... 0.00% Retained on a 1-inch (round openings) screen....... 30 to 70% Retained on a 14-inch (round openings) screen....... 70 to 85% Retained on a }4-inch (round openings) screen....... 100.0% A tolerance of five (5) per cent shall be allowed for wear in size of openings of all screens. Unless approved by the Engineer, no broken stone aggregate shall be used which has a French coefficient of wear less than six (6). The right is reserved to reject for cause any and all stone or gravel delivered on the work. Coarse aggregate consisting of crushed stone shall be of uniform character quarried from strata of approximately equal hardness, and the right is reserved by the State to forbid the use of crushed stone aggregates from any quarry when the character of the stone in the breast being operated and the mode of operation in blasting and handling is such as to make improbable the furnishing of uniform and graded crushed stone aggregate free from clay, silt or loam. The word ‘“‘stone,” if used on plans or elsewhere in specifying concrete proportions shall be understood to be coarse aggregate as herein defined. The right is reserved by the State to forbid the use of gravel pebble aggre- gate from any plant where the character of the material in such plant, or the mode of operation in such plant, is such as to make improbable the furnishing of hard and reasonably uniform well graded pebble aggregate, free from clay, silt or loam. 212. Water.—All water used in concrete shall be subject to the approval of the engineer and shall be reasonably clear, free from oil, acid, alkali or vegetable substances and shall be neither brackish nor salty. 213. Mixing.—The concrete shall be mixed in the quantities required for immediate use and any which has developed initial set, or which does not reach the forms within thirty (30) minutes after the water has been added shall not be used. Unless hand mixing is specially permitted by the engineer, the mixing shall be done in a batch mixer of approved type which will insure the uniform distribution of the materials throughout the mass so that the mixture is uniform in color and smooth in appearance. ‘The mixing shall continue for a minimum time of one (1) minute after all the materials are assembled in the drum, during which time the drum shall revolve at the speed for which it was designed, but shall make not less than fourteen (14) nor more than twenty (20) revolutions per minute. Where a fraction of a sack of cement is used the method of weighing or measuring shall be approved by the engineer. 214. Hand Mixing.—When hand mixing is permitted it shall be done on a watertight platform. The fine aggregate and cement shall first be mixed until a uniform color is attained and then spread over the mixing board in a thin layer. 132 CONCRETE PRACTICE The coarse aggregate which shall have been previously drenched, shall then be spread over the fine aggregate and cement in a uniform layer and the whole mass turned after the water isadded. After the water has been added the mass shall be turned at least four (4) times and more if necessary to make the mix uniform in color and smooth in appearance. Hand mixed batches shall not exceed one-half (14) cubic yard in volume. 215. Retempering.—All mortar and concrete shall be used while fresh before the initial set has begun. No retempering of mortar or concrete shall be allowed. 216. Consistency.—The consistency of the mix of the concrete shall be such that the mortar clings to the coarse aggregate. It shall not be suffi- ciently soft to flow rapidly or segregate. When the concrete is allowed to drop directly from the discharge chute of the mixer, the center of the pile of concrete shall flatten, but the edges shall stand up and not flow. The water shall be accurately measured and gauged and shall be automatically dis- charged into the drum with the aggregates. Quantity of water to be used shall be determined by the engineer and shall not be varied without his consent. 217. Depositing Concrete.—Concrete shall be so deposited that the aggre- gates are not separated. Dropping the concrete any considerable distance, depositing large quantities at any point and running or working it along forms, or any other practice tending to cause separation of the aggregates will not be allowed. Throughout the placing of the concrete in the forms, the mass shall be puddled or spaded sufficiently to insure perfect contact and bond with the reinforcing bars, and perfect contact with the surfaces of the forms. Smooth, finished surfaces shall be obtained by working the finer materials against the forms. Faces which show in the finished work shall be true to form intended and shall be wholly free from swells, ridges, holes, cavities, mortar shortages and so forth. Wherever practicable, concrete shall be deposited continuously for each monolithic section of the work. All floors and other thin work shall be placed full thickness. All slab and deck girder spans shall be placed ee sas: to the top of the wheelguard in a single operation as outlined below, and the contractor shall, before beginning this part of the work, have sufficient material of all classes on the ground, adequate equipment, and the necessary labor force available to finish the work. On through girder and slab spans the forms for the railing shall be assembled sufficiently so that they can be set in place without delay. Concrete in the railings shall be poured the day after the concrete in the floor has been placed. Slab spans shall be placed in longitudinal strips. Concrete shall first be placed in the middle of the span and carried in both directions full height uniformly towards the ends of the span. Pouring shall commence at the curb and continue across the roadway. The width of strips shall be such that the concrete in any one strip shall not take its initial set before the strip adjacent is poured. In case the mixer is disabled, a vertical joint shall be CONTRACTS, SPECIFICATIONS, AND PLANS 133 made parallel to the center line of roadway and enough concrete shall be mixed by hand to complete the strip. Deck girder spans shall be placed in longitudinal sections. Concrete shall first be placed in the middle of the span and carried in both directions full height uniformly towards the end of the span. Pouring shall commence at one curb and continue across the roadway. The width of sections shall extend between points midway between girders. In case the mixer is disabled, a vertical joint shall be made parallel to the center line of roadway and enough concrete shall be mixed by hand to complete the section. This joint is to be placed at the edge of one of the sections. To prevent a honey- combed bottom surface of the girders and before any concrete is deposited, not less than a three (3) sack batch of 1:2 cement grout shall be placed in the center of the girder. Concrete in walls shall be placed in continuous horizontal layers extending from end to end of the wall. Whenever Stops are made, the top surface shall be leveled off in a horizontal plane and grooved in the center with a 4” 4” timber whose top face is flush with the concrete surface. The 4”X 4" timber shall be removed as soon as the concrete has taken its initial set. When new concrete is placed on concrete which has a complete or partial set, the surface shall be thoroughly cleaned and scraped to remove all rubbish, badly cured concrete, laitance or other material detrimental to the finished work. The old surface shall then receive a coat of neat cement paste applied immediately in advance of the first batch. Bridge floors shall be built true to the dimensions shown on the plans, and the curbs shall be cast in the same operation as the balance of the floor. The curb forms shall be built to correct alignment and the contour of the top of the floor shall be determined by a strike board cut accurately so that the finished floor will conform to the dimensions shown on the plans. The top surface shall be floated to an even surface. Curbs shall be finished with a metal trowel and brushed. Corners shall be rounded with an edging tool. - Face of curbs shall be bricked. Sidewalks shall be metal trowled and brushed. Arch rings shall preferably be placed entire or, where this is not practi- cable, in monolithic rings with vertical joints parallel with the center line of the roadway, and each day’s work shall finish with one of these rings com- plete. Special care shall be observed to obtain good connection of spandrel walls to arch rings. Whenever concrete is desposited in freezing weather, special precautions shall be taken to avoid the use of materials containing frost, and thoroughly effective means shall be used to prevent the wet mixture from chilling or freezing. The water should be boiling and the aggregate heated to a temperature of not less than one hundred fifty (150) degrees Fahrenheit before the ingredients are placed in the mixer. The concrete shall be placed in the forms immediately after mixing. The entire work shall be covered in such a way as to retain the heat and prevent freezing of concrete in the wall. The use of salt to prevent freezing 134 CONCRETE PRACTICE ; shall not be allowed, and all concrete placed in freezing weather shall beat the contractor’s risk. Concrete may be deposited through water only by special authority from engineer, and that in writing. When so deposited it shall be by means of one or more tremies or chutes. ‘The lower ends shall be placed on the bottom of the foundation and the tremie kept filled, concrete escaping from the bottom because of a slight raising of the tremie. The surface of the concrete shall be kept level, and the work having once been started, shall be carried on continuously until that portion of the foundation to be deposited in water is completed. When the work is continued, the water shall be exhausted and the surface cleaned as hereinbefore described. The contractor shall have sufficient material on hand and labor available to guarantee that this can be done. The tremie shall be charged in such a way that the cement is not washed out of the concrete, and whenever the charge is lost, it shall be recharged in the same manner before placing is continued. In all cases where concrete is deposited through water, as hereinbefore described, the same shall be a Class A eee No concrete shall be poured unless an in- spector is present. 218. Forms.—All forms shall be built tight and substantial, so as to retain the finer parts of the concrete mixture, and to hold rigidly to place until the concrete has set. Forms which have sagged, bulged, or become warped or distorted in any way shall immediately be removed and the concrete affected thereby replaced with fresh concrete. The engineer shall have the right to require forms to be held in place by means of rods and waling strips. All lumber used for surface forms shall be of anevensurface. Where the concrete will be exposed to view, the forms must be built of selected lumber, sized and dressed, and free from defects which will show in the finished work. All joints shall be neatly fitted; triangular chamfer strips shall be carefully fitted with mitred corners. The forms for all concrete girders, railings, and arch spandrels shall be built with especial care from selected lumber, which shall have been carefully cut, planed and fitted in a planing mill, in such a way that the finished concrete work shall be of the exact dimensions shown on the plans. These forms shall be set up entire, firmly braced and inspected by the engineer before any concrete is placed in this part of the work. In framing centering for arches, allowance shall be made for settlement of centering, deflection of the arch after removal of centering and permanent camber. Centers shall be framed for a rise of arch 34 ¢ of an inch for each 10 feet in span greater than the rise marked on the drawings. The centers shall be so designed as to be rigid in place and free from all sagging and bulging. No concrete shall be poured until the engineer has inspected the centering and passed on its sufficiency. Effective means shall be used to prevent the adhesion of the concrete to the forms. The inside surfaces of all forms for girders, railings, or arch spandrels, or any other ornamental work, shall be well covered with shellac or a light oil one day before the concrete is placed. . CONTRACTS, SPECIFICATIONS, AND PLANS 135 Before concrete is placed, the forms shall be thoroughly wet and cleaned of all accumulations of rubbish. Care shall be observed to insure that the forms are cleaned in advance of pouring, from all dirt, or concrete which may have spattered and dried on the inside of the forms. In structures six (6) feet in span and under, the year of construction is to be stamped into the concrete on one end face of one wing wall or end wall in such a position as to be readily accessible for inspection. 219. Removal of Forms.—In order to make possible the obtaining of a satisfactory surface finish, forms, on ornamental work, railings, parapets, and vertical surfaces that do not carry loads and which will be exposed in the finished work shall be removed in not less than four (4) nor more than forty- eight (48) hours, depending upon weather conditions. Forms under slabs, beams, girders, and arches shall remain in place at least twenty-one (21) days in warm weather, and in cold weather at the discretion of the engineer. Forms shall always be removed from columns before removing shoring from -beneath beams and girders, in order to determine the conditions of column concrete. The removal of forms before the concrete has sufficiently set shall not relieve the contractor of responsibility for the safety of the work. As soon as the forms are removed all rough places, holes, and porous spots shall be filled, and all bolts, wires, or other appliances used to hold the forms and which pass through the concrete shall be cut off or pushed back with nail set one-half (14) inch below the surface and the ends covered with cement mortar of the same mix as used in the body of the work. As soon as the forms are removed from the base rail, coping or other ornamental work, the construction joints shall be opened and the edges beveled back sufficiently to prevent breakage at the junction points; the concrete shall be beveled back not to’ exceed an eighth of an inch both sides of all expansion joints in ornamental work. On spans carrying baluster railing, the centering shall be removed before the top rail of the railing is placed. 220. Surface Finishing.—The contractor shall build the forms, and place the concrete, in such a way that a smooth, even surface will be presented on removal of the forms, and the work of finishing thereby reduced to a minimum. . All concrete surfaces shall be well spaded by forcing a flat blade spade vertically down between the concrete and the form, and then by pulling the top of the spade away from the form so that the mortar will in all cases flow to the face of the forms. The rubbed finish shall be made by carefully rubbing the surface with a fine carborundum brick, immediately after removing the forms. The first step in this process is to moisten the surface with water, immediately follow- ing with the fine carborundum brick, rubbing in a circular motion. Only light pressure should be applied and the rubbing continued until all the air holes and small depressions are filled, and an excess of mulch is on the surface. The mulch should then be brushed out smooth with a long bristle paint brush. 136 CONCRETE PRACTICE After the concrete has been rubbed smooth and has set for a period of from five (5) to eight (8) days, it shall then be again rubbed, using a carborundum brick. Rubbing shall be continued until a smooth surface free from lumber marks and irregularities is obtained. In using carborundum brick, the surface to be rubbed may be moistened with water to facilitate the rubbing; the fine material loosened by the brick may be used to fill the pores in the concrete. On warm days when the sun is quite strong, rubbed surfaces should be covered with canvas to keep the sun from drying out the surface too rapidly, thus causing checking. Before final acceptance all dust left on finished surfaces by the action of brick shall be removed by rubbing with canvas, when the surface is perfectly dry. 221. Concrete Balusters.—The concrete in concrete balusters shall consist of a mixture of one part of cement, one-half of which is white cement, and two parts fine aggregate. The fine aggregate shall conform to the specifications for fine aggregate in. concrete pavements. The aggregate shall first be very thoroughly mixed in a dry state by shovel- ing on a tight board for not less than ten (10) minutes. The water shall then be added to produce a concrete of the consistency specified elsewhere in these specifications. After placing in the forms, the concrete shall be tamped with unusual care in order to insure that no voids remain and that the air pockets on the surface of the balusters are reduced to a minimum. After brushing, the balusters shall be carefully stored, sheltered from rain, sun or other damage, and cured under a damp canvas for a period of at least six (6) days. At the time the concrete baluster has reached the proper degree of set (approximately ten (10) days after pouring) it shall be carefully rubbed to a smooth, even finish with a fine-grained carborundum brick. All balusters shall be manufactured by skillful, experienced workmen, and no imperfect cracked or damaged balusters will be accepted. 222. Curing Concrete.—Careful attention shall be given by the contractor to the proper curing of the concrete. Handrails, floors and troweled sur- faces shall be protected from the sun, and in drying weather the whole structure shall be kept wet for a period of one (1) week. Concrete floor slabs may be covered with damp sand as soon as the concrete has taken its initial set and then kept wet for one (1) week. Other precautions to insure thor- ough curing of the concrete shall be taken by the contractor as directed by the engineer. The roadway shall be kept closed to traffic for three. (3) weeks or if in the opinion of the engineer the weather conditions make it advisable, the roadway may be opened to traffic in a shorter or longer period of time, provided the closed period shall never be less than two (2) weeks after the concrete is deposited. 223. Foundation for Concrete.—Where concrete is to rest on any exca- vated surface other than rock, special care shall be taken not to disturb the bottom of the excavation, and the final removal of material to grade shall not CONTRACTS, SPECIFICATIONS, AND PLANS 137 be made until just before the concrete is laid, except in concrete foundations for pavement. The excavation lines and bases of structures shown on the plans shall be considered only as approximate and they may be ordered in writing by the engineer to be placed at any elevation or of any dimension that will give a satisfactory foundation. Any additional concrete that may be required by the engineer below or beyond the line shown on the plans shall be paid for at the contract price. No structure shall be commenced without the engineer’s approval. All rock or hard pan foundation surfaces shall be freed from loose pieces, cut to firm surfaces, and cleaned to the satisfaction of the engineer before laying concrete. All seams shall be cleaned out and filled with con- crete or mortar, and payment for such concrete used in filling shall be made at the contract price for the class of concrete used. 224. Measurement and Payment.—The quantity of concrete to be paid for shall be the number of cubic yards under the various classes measured in place in the finished structure placed in accordance with the plans, or as ordered by the engineer. No payment will be made for any concrete outside of these limits nor for any concrete whose replacing is rendered necessary owing to lack of proper care, and the price paid per cubic yard shall include all materials, forms, labor and other incidental expenses necessary to satis- factorily complete the work as specified in the foregoing paragraph. Unless otherwise stipulated all excavation required for placing concrete shall be included in the price bid for concrete. Exercise.—If a reinforced concrete slab bridge was to be built of Class A concrete in Wisconsin during July and August, what clauses in the detailed specifications for Concrete in Forms would not be needed? JOB 37. PLANS Plans and drawings are used as a part of a complete contract to help the parties to visualize correctly the structures. Many details that are very difficult to describe with words are easily shown by means of drawings. In general, the complete plans for a concrete building may show the location of the lot, including its dimensions and boundaries and sometimes contours; basement, floor, and roof plans; eleva- tions; framing plans; sections; and details. In addition to these, there may be plans for plant layout, forms and framing, rein- forcement bending, various details, etc., according to the Judg- ment of the engineer or architect and the needs of the contractor. Plans for a concrete arch bridge would include the site, plans, elevations, stress sheet, sections, and details. The scales used for plans vary greatly, depending on the job in particular, and the opinion of the engineer or architect. Scales 138 CONCRETE PRACTICE of 14 or 1g in. to the foot are common for general ache and 34 or 1! Ve in. to the foot for details. When obtaining dimensions from plans, the distances given in figures will usually take precedence over the scaled distances. Tracing cloth, drawing paper, and blueprint paper often shrink a little with age, so that drawings which scale correctly when they are made will not scale correctly a few months later. In most drawings, various symbols are used to take the place of words. ‘The selection and use of symbols vary somewhat in different localities, in different offices, and with different trades. Some of the common symbols used in concrete work are: Ge means 6 in. 3’ means 3 ft. 40’’ means 4 sq. in. 2'O’ means 2 sq. ft. 16’’@ means -in. round rods ¢ means center line. 34 4’'(A means 34-in. square rods 3” o.c. or 3’’c.c., means that rods are spaced 3 in. on centers or from center to center. Common abbreviations for words such as lb. for pounds; in. for inches; ft. for feet; M for thousand; squares for 100 sq. ft.; sq. ft. for square feet; cu. ft. for cubic feet; sq. yd. for square yard; cu. yd. for cubic yards; bd. ft. for board feet; etc., are also used in concrete work. When reading plans and blueprints, information for some particular item is usually wanted in regard to its location, dimen- sions, kind, finish, or quantity. Reading of plans and blueprints is not very difficult, but it does require careful attention to detail, especially upon the part of a beginner. Anyone who has com- pleted a drafting course in school, or who has had some experience in a drafting office, should have no difficulty in reading and understanding the average structural drawings. Drawings that are incomplete, inaccurate, or otherwise poorly drawn will cause trouble for any plan reader, quantity surveyor, estimator, or constructor. Plan reading is simply the examination of the drawing or blueprint, to secure some information that is shown in the drawings or blueprints. In the following job, there are complete plans for a reinforced- concrete slab highway bridge. An examination of these drawings will bring out much information in regard to plans for concrete work, especially if the questions in the following job are carefully CONTRACTS, SPECIFICATIONS, AND PLANS 139 answered. Ina later job, a quantity estimate has been prepared for this particular concrete structure. Checking this quantity estimate against the plans and specifications will give the average student a good understanding of what is meant by plan and blueprint reading. Exercises.—What are plans or drawings? What is the object of making drawings for a concrete structure? Name the drawings which, in your opinion, should be provided for a one- story concrete garage with basement. What scales would you use in preparing the general and detailed drawings for this garage? What is plan reading? JOB 38. STANDARD PLANS FOR A REINFORCED CONCRETE HIGHWAY BRIDGE The plans shown in Fig. 71 are standard plans for a reinforced concrete slab highway bridge, with a clear span of 16 ft. and a 28-ft. roadway. ‘These plans contain a half-side elevation, a half section just inside a rail, a half-end elevation, and a half section through the paneling at the center of the span, as well as a bill of reinforcing steel, a detail of the drain, general notes, and estimated quantities. In Fig. 72, are shown the horizontal plan, front elevation, end view of a wing, and sections of a reinforced concrete abutment suitable for the slab bridge shown in Fig. 71. Note that. several dimensions are omitted in the abutment plans. These dimen- sions are to be filled in when the height of the abutments, width of roadway, clear span, and depth of the reinforced concrete slab bridge have been determined for the particular job in question. Evxercises.— Using the bill of bars, check the total weight of reinforcing steel required in the plans for the reinforced concrete slab bridge shown in Fig. 71. What would be the required width of the bridge seat in the abutment plans of Fig. 72 to care for the slab bridge of Fig. 71. What would be the required depth of the bridge seat notch? JOB 39. PLAN READING Plan reading is simply examining the plans to secure some desired detailed information. Any person who can read English fairly well, and who will pay careful attention to details, should not have much difficulty in learning to read plans. CONCRETE PRACTICE 140 - ABMPBOL JOO} JYSte-AJUNMY PUB UBdS JOOJ-U994}XIS JO QUIS 0Ja10U0D PodIOJUIOI B IO} SUVTG—'TZ ‘DIT AVMQV04,,0;82 N¥dS,0-91 GTS FLIYINOD CFIYOANITY NOISSINWOD_AVMHOIH _NISNODSTAC. MOV 9 Jayf4 LUlor eisuiodxz F real fe ee | PeAlild LUIOL UOISUBOXZ Dbal 2 'SulQlg #OG0E ‘jaa Buiqajulay ‘SPA 12 §L2 1 AasIUOD BOK, panosddo fo aq OY Jays {iol Uorsuodxz ‘SHIDYD 0G DI[jofaull KG B00/0 Lil Pjaly ag JOYS {UBWBQOJUIAS |] "SUIDID DUNOIO {IAG aq ||OUS S10G J00/f aSlanSuUay puo JOUIpNyIbU0T ‘$109.25 DUD $J0G,/5, {Ua2D/po Jog Daslanad 20 $PUZ ‘S10G,25, aly YjIM afou AAO S10G, 1S, BY :SMO/Of SO AQ JOYS $id JOUIPN{OUO ayf JO {UaWaOUDLIO ay payloads S1og JO 0210 ayy af jonba UOHIaS {BU JO S1OG PUOG [ODIMOYDAW 3G /JOYS JUBWADIO{UIAY suoy A10d0sd F-2-1 'Y, SSOP AQ /JOYS 2f2/IUOD “SHLON TVYINID Masddy ‘wan pazilonob a606 9/ 40 apdUl ag {JOYS SUIQIG MVYI SO WLI c= NOILVAFTTA INF ATVH ‘OUND O OIND Waly DUALXO Y {UaUwnod BfA/2UOD JG} YON 2 'SMPOI,9 Of GiNr “Yo pula punoy 79581 [ay er aararsUaL, es samo NaF |ES| a CUi[QAl Ul [OWL Spee SYvE FO 711/19 INITINYA NAHL AVMGVOY FO NOILDTS SSOYD FTVH | \Bynogo uMks> ¥-Y NOILDZS STVH 4202 I*---B yn0go "uik> Falfty {UIOL UO/SUBAKZ z- 141 CONTRACTS, SPECIFICATIONS, AND PLANS ‘sJUSTA}NGB’ uBds-qBIS OJa1NUOD PodIOJUlIeI IO} suUvTG—'Sy ‘DIY 4aauibuz AOMYENH HOLS spanoiddy ZHL YOF SLINAWLOAV ALSYDNOD QsIDYOINIEY NOISSINWOD AYMHOIH NISNODSIM ‘uUods auo - aInjonASsadns (DOG ayy Ul /ODu-La) NOILYIO7 “DDVdSLONIT| FZIS| SYVG JO 77/2 ‘Jans burasojujey afa1guo) SFILILNYNO GFILVWILSF payloads S109 JO DBIO alt af jonba UouIas fall JO S109 PUOFT [ODUOYIAU! AQ Wes AUPLIDDIOJUIBY 3/ 219u02 JO sebpa pasodxea janeg (suousodosd p:2:/) ¥,SSD/2 29 [JOYS HYEIDUOD |] ‘GUIMQIP 3/02$ {OU OG SFLON TYHINID fUallia21O{Uley PUuo SUOISUBLIIG Y¥IOM{DB\) BUIMOYS Wre9Ovid NOILYIOT ,7al2Uuo? Bupypisodap, 49PUN SUOYOIYIIAAS 3aS LN/IOL NOILPNALSNOD TWHIGAL Sbuyoos Tt SUOISUBLIG OUILLOOY BLUIIMOYS <—ADMPOOLY JO B 420G0 ‘UKs AMGY IOP SONIM FO V-Y NOILIFS : HOLLOW INMSUO, NO NOILDIS MIA GNF Laoag. / Ol NOILVAFTF LNOAF Aompooy 40d £090 WKS 142 CONCRETE PRACTICE The following questions and answers in regard to the reinforced concrete slab bridge, shown in Fig. 71, will illustrate to some extent what is meant by plan reading. Question: What is the depth of the slab at the center of the roadway? Answer: From the half-end elevation, the depth is shown to be 1 ft. 2 in. Question: What is the depth of the slab near the rail? Answer: From the half-end elevation or the half section A-A, the depth is shown to be 1 ft. 1 in. Question: How far above the bottom of the slab is the main tensile rein- forcement (7-in. round bars) placed? Answer: From half section A-A, the centers of the %-in. round bars are to be 17% in. above the bottom of the slab. Question: What is the total length of the slab? Answer: From the half-side elevation and the half section A-A, the total length of the slab is 18 ft. 6 in. Question: What is the total overall length of the bridge? Answer: From the half-side elevation and the half section A-A, the total overall length of the bridge is 18 ft. 6 in. plus 4 in., or 18 ft. 10in. The ends of the rail extend 2 in. beyond each end of the slab. Exercises.—Where are the drains placed? How many drains are required? How many main reinforcement bars (7-in. round bars) are ‘required? What is the total width of the top part of the bridge rail? _ How high is the bridge rail above the curb? How high is the curb? How wide is the curb? Are there any sidewalks provided on this bridge? Where are the expansion joints located? What are the dimensions of the recessed panels in the bridge rail? How many of these recessed panels are there? What is the spacing of the main reinforcement bars (7-in. round bars) in the floor slab? What is the total number of bends to be made in these 7-in. round bars in the floor slab? What is the spacing of the transverse reinforcement (14-in. square bars) in the floor slab? How far from the center of the slab are each of the three bends of the %-in. round bars made? (See half section A-A.) What are the dimensions of the notch left in each end of the bridge floor slab for the concrete pavement? What kind of reinforcement bars are required? (Plain or deformed?) What kind or class of concrete is required? What is the ‘“‘crown” in inches provided in the center of the bridge floor slab? What is the total overall width of the bridge? SECTION IV ESTIMATING JOB 40. ESTIMATING IN GENERAL The work of estimating is commonly divided into two parts: (1) estimating quantities or “taking off,” and (2) estimating unit costs. A simple concrete job may be divided into the following parts in regard to quantities and units: . Excavation in cubic yards. . Forms and false work in square feet of form surface. . Concrete in cubic yards. . Steel in pounds or tons. . Finishing in square yards. . Cleaning up for job. For a more complicated job, such as a reinforced concrete building, other items should be added, as masonry (brick, stone, terra cotta) in cubic feet or per thousand brick or block; lath and plastering in square yards; building trim, windows, and doors; hardware; iron work; roofing in squares of 100 sq. ft. or sq. yd.; flashing; painting in square yards; sundries; subcontracts; and general overhead (if not previously apportioned). Each of these divisions may be subdivided into the following _ parts: a. Material in units suitable for each kind of material. b. Labor in hours. c. Plant in hours or days. d. Overhead in hours. Sometimes an estimator will use the subdivisions a, b, c, and d as the main divisions and then use the divisions 1, 2, 3, 4, etc.; as subdivisions. A complete estimate of the quantities of materials may be said to be a “quantity survey. In some localities the ‘quantity surveyor” prepares a list of materials for any given Job and all 143 Oot WN & 144 CONCRETE PRACTICE contractors, who bid on the job, use this list. The contractors make their own individual estimates for labor, plant, and overhead. The preparation of a list of materials is known as the “take off.” The estimator tabulates all of the different materials as to kind, number, size, weight, volume, or other units used. The selection of units for different materials will be explained in more detail in later jobs. In estimating the quantity of labor for a given job, the total number of labor hours or man hours for each class of labor and each kind of work is tabulated. It is often difficult to estimate accurately the number of hours required for a laborer to perform a given task, as some laborers work faster or slower than the average. When a contractor has had practically the same gang working for him for a few months, his experience will enable him to estimate quite closely as to the amount of work this particular gang will do in a day or an hour. The selection of the plant will often depend on the machinery that the contractor has available for the job. The estimate of the time that the plant will be used may be based on the total time that the plant is held available for the job, or on the total time that the plant is run, or on both. The estimate of overhead may be given in hours or days that will be required of the superintendent, engineers, inspectors, clerks, stenographers, watchmen, etc., to care for the work of this particular job. When estimating unit costs, the costs of the materials at the job are usually computed. This cost includes first cost, freight, _unloading, cartage, storage, inspection, testing, and insurance. Total labor costs are found by multiplying the hours estimated for each class of labor by the corresponding wage rate per hour, and then adding results. Plant costs usually include cost of installation, maintenance, operation, removal, interest on investment, and depreciation (proportionate part of first cost of plant). These costs often include the labor costs of machine operators, such as hoisting engineers, firemen, etc. To get unit costs, the total cost of the plant on the job is computed and divided, either by the total ~ number of hours that the plant is held available for the job, or — ESTIMATING 145 else by the number of hours that the plant is actually operated on the job. Some estimators use two plant hour rates; one when the plant is idle, and another when the plant is running. Overhead costs include such general office and other labor costs that are not considered as direct productive labor on the job. Other overhead costs are insurance, rents, office stationery, expense of plans and specifications, interest, legal expenses, travel- ing expenses, sundries, etc. ‘These overhead expenses are often apportioned to the several parts of the job according to the labor hours or labor costs of these parts, though sometimes some of the overhead costs are assigned to the materials and plant. Last, but not least in importance, is the profit. The amount of profit is usually expressed as a percentage of the total cost of the job. This percentage usually varies from about 8 to 15 per cent, depending on the contractor’s desire for the work, what he thinks is fair, and what he thinks he can get. For small jobs, 15 per cent is a common figure for profit with 12!4 per cent for medium jobs, 10 per cent for large jobs, and possibly 8 per cent for very large jobs. The percentage of profit added also depends, to some extent, on how often payments are to be made and in what amounts. On large jobs, payments up to about 85 per cent of the total work done are made each month. Exercises —Name the six main divisions of concrete work. Name the four subdivisions. What is a “quantity survey” and how is it made? What is a ‘‘take off?” What things are usually included in material costs? What is meant by overhead and what does it include? JOB 41. ESTIMATING EXCAVATION While it is comparatively easy to compute the quantities for excavation, there are several items which will affect the total labor required and the costs. Excavation is usually divided into two classes: (1) general excavation, such as excavating for a large cellar or making a cut for a railroad or a highway; and (2) particular or special excava- tion, such as digging narrow trenches, footing holes, ete. Gen- eral excavation may be done by hand, scrapers and horses, or steam shovels, while hand work is practically always required for special excavation. 146 CONCRETE PRACTICE The time and cost of excavation also depends upon the charac- ter of the material to be removed. A cubic yard of hardpan may require from two to four times as much labor as a cubic yard of loam. In computing quantities for excavation, the estimator must be careful to include the dimensions from outside to outside of footings, and from the top of the grade to the bottom of the base- ment floor. In the ‘‘take off,’’ each item of general and special excavation ° must be listed separately, with dimensions and quantities, as well as the kind of soil. Sometimes the earth will retain its verti- cal position without support. In other cases, the earth walls will require sheeting or bracing. In general excavation with steam shovels, it is sometimes more economical to omit the sheeting and slope the banks. When computing quantities where the surface of the ground is sloping or uneven, the horizontal projection may be divided into a number of convenient squares and rectangles, and the average height of each section estimated. | The following table gives the angles of repose for various kinds of earth: ANGLES OF REPOSE Angle with horizontal in ; degrees Material Dry | Moist Wet 30-45 20-40 week ae a aoe CER aes Setar Pee ets ey eee 25-45 25-30 C1 Ve OO 6 Oe wm B00. ete 6 ce 0 16. & 8 co '8\ ‘B61 \6 © Ole) (6. exe Slap ne “ec ew eb O28) ee) ee) We Oe 6 The work of excavation done per man per hour varies greatly with the skill of the laborer, his inclination to work, and the character of the soil. The following tables give approximate values: ESTIMATING 147 SHOVELING—CuBIC YARDS PER MAN PER Hour INCLUDING LOOSENING WITH Picks AND SHOVELING INTO WAGONS oR TRUCKS Total lift not more than 6 ft. General excavation 220 phe ae 20 ie een Si ee Me, Special Material Dry Wet ee Cubic yards per hour So APO 0 0.60-1.60 | 0.50—-1.00 | 0.30-0.70 ead EEL sie. d's dot ses 0.40-1.00 | 0.25-0.50 | 0.20-0.40 ieaepOLIANC. CIAY) ..). 6... 2... ku 0.30—0.60 | 0.20-0.40 | 0.15-0.35 ST ela Cin 0.25-0.50 | 0.15-0.35 | 0.10-0.30 SHOVELING LOOSENED MaTERIAL—CuBIC YARDS PER MAN PER Hour WHEN SHOVELED INTO WAGONS OR TRUCKS Total lift not over 4 ft. Material Cubic yards per hour Preece Ontaenr ExXCAVAUION. . 2.2.0... bea ee es 0.90-1.75 PTET OMEOIIWEXCAVATION... 04.606. ee wey eee eee 0.85-1.65 Pea eee Cee ayn EXCAVALION..; 02. ca. ee pees 0.60—1.30 Pee Pe KCAVAUON 1. cs ec ws ce bee ce eee 0.50—-1.20 eee IMPrOTOreTONGU LO WOCON . 2... ca. es cca eee tee ele hee 2 .00—4 .00 Stone and gravel from ground to wagon................ 1.50-3.50 Peer eeOMO TOU GOLWAdON.... oo. cre tn ee Oe ee bam ee 1.50—-4.00 A driver and helper with two horses and a plow can loosen from 15 to 40 cu. yd. of earth per hr. depending on the character of the soil. Heavy soil may require four horses. CAPACITIES OF VEHICLES Ordinarily taken as 80 per cent of rated capacity Vehicle Cubic yards RRR oa ernie acc g soe 4 ial'o, dees gun Bao as 0..10-0 7.15 Reine VE te Coir 2S ye ahh. s ie cp eiiess soe ve ols plcaren © a's 0.10-0.25 Oe LETELR CET Cayce ae a ee 0.35-0.65 Pe OTSCVOUINPI WHEOD 08. 1. eu Phew ow ae lian 1.00-1.75 Dh CR, “0 US DRE SS a a He ge Gn 1.00—5.00 148 CONCRETE PRACTICE EconomicaL Haut (APPROXIMATE) Vehicle Distance Wheelbarrows Sunes ce oe ne ee Not over 100 ft. Drag scrapers; ccs ore eee Not over 150 ft. Wheel scrapers tcsvhicieuiin ks ten ee Not over 500 ft. Dump Wagonses fal feo ue his eee 500 ft. or over Auto TPUcks ee le fe ha ey ne Oho I he een 1000 ft. or over TIME FOR HAULING | Load, Unload, -3| eee Vehicle : ; travel, miles minutes minutes per hour Wheelbarrow.5 28 e152. ka. 1.00— 3.00 0.20 2 rae sera pera. = ee ee 0.25- 0.50 0.25 2 Wheel scraters tia. mxhee ae 0.25-— 0.50 0.25 2 Dump wWag0lay ee eeee es 1.00- 9.00 | 0.25-1.00 2 Auto truck saeny cer oe eae 1.00-12.00 | 0.25-1.00 8-15 Time required to load a wheelbarrow depends on whether one or two men are shoveling, and on the kind of material. Time required for loading a dump wagon depends on number of shovelers in hand loading, on operation of shovel in machine loading, and on conditions of work. GASOLINE OR STEAM SHOVEL CAPACITY Size of shovel, cubic yards Cubic yards per minute 34 1.00— 2.50 1% 1.50— 4.00 114 2.00— 5.00 134 2.50— 6.00 2 3.00— 7.00 21 4.00— 9.00 3 5.00-11.00 The output of a steam shovel per minute depends on the amount of moving it must do, the time required to move the loaded truck and place an empty truck in position, the skill of the shovel operator, the speed of the shovel, and the character of the soil. Hence, all figures given above are approximate. Steam ESTIMATING 149 shovels are often not economical when the amount of general excavation is less than about 1500 cu. yd. BacKFILLING—CuBIc YARDS PER Man PER Hour WHEN MATERIAL Is SHOVELED INTO TRENCH AND TAMPED A LITTLE Cubic yards per hour Material per man Sos dai, | Se eee 1.5-3.0 Br IA ER ck Se es ee ee 1.0-2.5 PRE PTPPOUP GO OIAYS fii ced bee een 0.8-2.0 When the backfill material has to be wheeled, the amount of backfill per man per hour will be reduced proportionately. Sheeting and bracing for trenches is usually estimated by the square foot of surface measurement of the earth retained. The amount of lumber in board feet for sheeting may vary from about 100 to 400 bd. ft. per 100 sq. ft. of surface measurement of retained earth. The cost of lumber for trench sheeting may vary from about $35 to $60 a thousand board feet. When the trench sheeting can be removed and used again, the wastage of lumber varies from about 20 to 50 per cent. One man will place from 7 to 10 sq. ft. of sheeting per hour and remove from 20 to 40 sq. ft. per hour depending on the depth of the trench. The cost of labor per hour varies greatly in different localities and in different years, so that a knowledge of the local labor supply is essential in preparing a cost estimate. The following approxi- mate values in preparing a cost estimate will be used: Wage or cost per Kind of labor hour, dollars erp ae Se es ae fs wins ¥oe WN Sane oa 0.40—0.60 ee ae Be ies oc. 8858 G sau age eS PS KB 0.80-1.40 Tear RNs. y God coef lil erscyicpea a Y ode ed oma ues 1.00-1.50 Man and team with scraper or wagon................ 1.00—1.50 Ey EGS be 0 oe) 2.00—-5.00 ire novel. Witt ODCYTALOL<... 5.4.2. uc sleet wee nee 2.50-7 . 50 Illustrative Problem.—Prepare an estimate of cost of excavation of 20,000 cu. yd. of general excavation, 400 cu. yd. of special excavation, 300 cu. yd. of backfill, and distance of haul of 1.5 miles. Assume medium 150 CONCRETE PRACTICE soil which will expand 20 per cent on excavation. Wage of unskilled labor is 50 cts. per hr., foreman $1 per hr., man and team and 2-cu. yd. dump wagon is $1 per hr., driver and 214-cu. yd. auto truck is $3.50 per hr., operator and 34-cu. yd. steam shovel is $4 per hr. Estimator has choice of dump wagons or auto trucks. Allow 15 per cent for overhead expenses and 10 per cent for profit. Compute total costs and cost per cubic yard. Cost of General Excavation Assume output of steam shovel to be 1.50 cu. yd. per min. $4.00 = SBGoscnl a Ga $0.0444. Time of haul for 1 team and wagon = loading 1 min., unloading 0.50 min., time on road 90 min., totaling 91.50 min. per load. 1.00 X 91.50 1 GO alae $1.525. Cost per cubic yard = $1.525 + 1.5 = $1.0167. Time of haul for auto truck = loading 1.33 min., unloading 0.50 min., time on road (assuming 8 miles per hr. loaded and 15 miles per hr. empty) 17.25 min., totaling 19.08 min. per load. Cost of digging per cu. yd. Cost per load at $1 per hr. = < 9. Cost per load at $3.50 per hr. = ae = $1.113. Cost per cubic yard = $1.113 + 2.0 = $0.5565. 20,000 Total time required for general excavation = 1.50 x 60 = 222.22 hr. Cost of foreman = $222.22. Cost of f bi d = at Sone ost of foreman per cubic yard = 55 Gog = 80. : Cost per cubic yard with trucks =$0 .6120. Use auto trucks. Cost of 20,000 cu. yd. = $12,240 + $1836 overhead + 10 per cent of ($12,240 + $1836) profit = $15,484, or a cost of $0.774 per cu. yd. Cost of Special Excavation and Backfill For special excavation, assume labor output with shovel as 0.30 cu. yd. per hr. Cost per cubic yard at $0.50 per hr. = a8 = $1.667 per cu. yd., or $667 for the job. Assuming eight men in shovel gang, time required will be ae = 167 hr. Cost of foreman = $167 for job, or $0.418 per cu. yd. Cost of backfill, assuming 1.50 cu. yd. per man per hr., is a = $0.333 per cu. yd., or $100 for the job. 300 aes Ram Cost of foreman for the backfill = $25 for job, or $0.0883 per cu. yd. Assuming eight men in gang, time required will be ESTIMATING 151 Now there were 400 — 300 or 100 cu. yd. of special excavation to be hauled away. Using auto trucks, and assuming that this material is shoveled into the trucks as it is excavated, it will require or 50 min. to load a xX 6 8 X 0.30 truck with 2 cu. yd. Total time of auto truck for one round trip equals 50 + 17.25 + 0.50 = 67.75 min. Cost per load = st SE = $2.3/1. Cost per cubic yard = zeae. = $1.186. Total cost of special excavation and backfill = $667 + $167 + $100 + $25 + $119 + $162 (overhead) + $124 (profit) = $1364 or a cost of $3.41 per cu. yd. based on 400 cu. yd. Total cost of general and special excavation and backfill = $15,484 + $1364 = $16,848 for the job. Cost per cubic yard based on 20,400 cu. yd. = $0.826. Ezxercises—Make an estimate of the cost of digging a basement 25 X 32 ft. and 6.5 ft. deep in medium soil, assuming 10 per cent to be special excava- tion. Use drag scrapers with an average haul of 65 ft. Assume wages of man and team at $1 per hr., and helper and shoveler at $0.50 per hr. No foreman on the job. Allow 15 per cent for overhead and 1214 per cent for profit. Compute total cost and cost per cubic yard. Make an estimate of the cost of digging and moving 35,000 cu. yd. of sandy loam using a 34-cu. yd. steam shovel, and 114-cu. yd. (net load) dump wagons. Length of haul averages 0.35 mile (0.70 mile for round trip). Assume capacity of shovel at 1.5 cu. yd. per min. (loading 1 wagon each minute) and cost at $4.50 per hr. Cost of man, team, and wagon is $1.10 per hr. Assume foreman at $1 perhr. Allow 17 per cent for overhead and 8 per cent for profit. Compute total cost of job and cost per cubic yard. How many: teams and wagons would be needed to keep the shovel working at assumed rate? JOB 42. ESTIMATING FORMS The unit of measurement for forms should be the actual area in square feet of the surface of the concrete in contact with the form. The estimated cost of the forms should include cost of struts, posts, bracing, bolts, wire, ties, oiling, cleaning, and repairing, but should not include cost of staging and bridging. Forms for each different part of the structure should be listed and described separately. Forms for moldings, window sills, and copings are measured by the lineal foot. No deductions in form measurement are made for openings having an area of less than 25 sq. ft., because the extra labor in forming around the openings will often cost more than the value of the lumber saved. No allowance is made for construction joints except in very large structures such as dams. 152 CONCRETE PRACTICE Forms for How measured Floors h: ve in ee ee Total area in square feet. W alle Sic Sonas eee eee Total area in square feet. Forms may be placed on one or both sides. Columns) desc tptero ere: Circumference of the column in feet times the net height in feet from floor to floor. Column caps, drops, bands, | Total area in square feet. etc. ROOTS ic cos ate el Re Total area in square feet. When the slope of . the roof with the horizontal exceeds 25 deg , the upper side of the roof requires forms. Footings 3 fr cone eee Total area in square feet of concrete surface next to forms. Beams and girders.......... Total area in square feet. For a beam this is equal to the net length between columns or supports times the sum of the breadth and twice the depth. Staging and bridging........ No definite rules. Total number of thousand board feet required should be computed. Moldings and cornices...... Total number of lineal feet. . Other dimen- sions should be noted. Window sills, and copings... .| Total number of lineal feet. Other dimen- sions should be noted. Stair: Tek) oa oe en Total area in square feet, composed of area of the under side, areas of ends, and areas of risers. APPROXIMATE MATERIALS AND LABOR PER 100 Sq. Fr. or Forms, ASSEMBLING AND ERECTING Lumber, Nails or Kind of forms board bolts, Labor, hours feet pounds ; Footings and piers.....%....... 200-350 Way a a>) 5.0-11.0 Walls and partitions, 2... .5... 200-270 1.0-1.4 8.0-14.0 Ploors: 3.3+ a2 enone 180-280 0.7-1.2 4.0-12.0 Roots 273.0 erea ee ae 200-300 0.8-1.3 4.5-14.0 Golutons’. 32a 52 eee 190-320 0.7-1.4 6.0-12.0 Column Gapsicsecs eee 200-400 0.8-1.4 8.0-18.0 Beams and girders...........:. 300-700 0.9-1.6 9.0-14.0 Stairs 22505, ah eee eae ee 300-600 1.0-1.6 10.0-20.0 Molding and cornice!.......... 200-800 0.8-1.8 8.0-20.0 Sills and jintele)s suas 250-800 0.8-1.6 7.5-16.0 1 Per 100 lin. ft. ESTIMATING 153 Staging and bridging should be estimated separately for each job, and no general values for this work can be given. Stripping and cleaning of forms will require from 2 to 5 hr. of time per 100 sq. ft. of forms. When the work permits re-use of forms of certain types, per- haps from 40 to 80 per cent of these forms may be re-used after repairs have been made. The amount of labor required for repair of forms varies greatly and may be estimated at from 2 to 5 hr. per 100 sq. ft. of forms. The extra lumber for form repairs may vary from about 40 to 200 bd. ft. per 100 sq. ft. of forms. After old forms are repaired, they must be erected before use, and the labor of erecting will be from 25 to 50 per cent of the total time of assembling and erecting new forms. Form work is often all done by carpenters, but, when possible, a combination gang of carpenters, ‘‘handy men,” and ordinary laborers should be used to save expense. The proportion of the different classes of laboring men will vary in any gang, but one- third carpenters, one-third handy men or rough carpenters, and one-third laborers will not be far from the average. The cost of form lumber may vary from about $380 to $60 per thousand feet board measure, with average values of from $35 to $50. The average cost of laborers will be about as follows: carpen- ters $0.80 to $1.50 per hr.; handy men or rough carpenters $0.50 to $1 per hr.; and laborers from $0.40 to $0.60 per hr. Foremen will cost $1 to $2 per hr. and a good superintend- ent from $1.50 to $3 per hr. Overhead, labor insurance, etc. will vary from 10 to 20 per cent of the total cost, with 15 per cent as an average value. When based on labor costs alone, overhead costs will vary from 15 to AQ per cent. Profit on form work (when figured separately) will usually vary from 10 to 25 per cent. When there is no salvage value to the old form lumber, the total costs will usually be higher and the percentage of profit less. When some of the form lumber may be salvaged, it is often difficult to estimate this value, and the estimator may guess at a low salvage value and a low percentage of profit or vice versa. When forms are stripped, the salvage value of the old 154 CONCRETE PRACTICE form lumber may be from 20 to 90 per cent of its original cost, depending upon care exercised by the stripper, and the possible use to which the old lumber is to be put. Nails and bolts will cost from about $0.04 to $0.06 per Ib. on the average, when purchased in quantity. Oil for oiling forms will cost a few cents per 100 sq. ft. of surface, say from $0.03 to $0.07, depending on kind and price of oil. Exercises.—Make a complete estimate of the form lumber required in 1000 bd. ft., pounds of nails and bolts, labor in hours, and costs of each for the following form surfaces: foundations and footings 785 sq. ft.; walls 2180 sq. ft.; columns, 3150 sq. ft.; column heads 1780 sq. ft.; floors 14,200 sq. ft.; beams 3160 sq. ft.; roofs 4100 sq. ft. Take unit prices as follows: Form lumber $38 per thousand board feet delivered at the job, bolts and nails $0.05 per lb., foreman $1.50 per hr., carpenters $1 per hr., handy men $0.75 per hr., and laborers at $0.50 per hr. Assume that salvage value of form lumber will be 65 per cent. Allow 15 per cent of total cost for overhead and 10 per cent for profit. Forms are to be made and erected and later stripped and cleaned. JOB 43. ESTIMATING CONCRETE In estimating concrete quantities, it is customary to use a sheet or page for each different mix, arranging columns on each page about in the following order: Description (footing, beam, etc.). Dimensions (of each unit in feet). Volume (cubic feet or cubic yards). Other columns may be added for unit and total prices, etc. In ‘‘taking off”? quantities of concrete it is customary to begin at the bottom or one end of the structure and go over it system- atically. In a concrete building, the order of ‘take off’? would be about as follows: Footings. Foundation walls. Columns (interior and exterior). (Ordinary column caps and brackets are usually included with columns.) Floor and roof slabs. Drop panels. Beams and girders (exterior and interior). Partitions. Window sills and copings. ESTIMATING 155 Stairs. Sidewalks and drives. In general, all concrete is measured net, as fixed or placed in the structure. Units of measurement are cubic yards or cubic feet, cubic yards being the common unit. No deductions are made for steel beams and reinforcement in the concrete unless the steel has a cross-sectional area of more than 1 sq. ft. No deduc- tions are made for pipes or holes having a sectional area of less than 1 sq. ft. Each mix of concrete should be measured and described separately, and the concrete in different members of the structure should be measured and described separately according to location or purpose of the work. Many rules are given for measuring stairs, but the best rule is to compute the quantity of concrete required in cubic yards by some simple method. Sidewalks and pavements should be measured by the square foot or square yard with the thickness and mix stated. The unit of measurement for precast concrete work is usually the cubic foot. Curbs, gutters, window sills, lintels, moldings, and such work are often measured per lineal foot, other dimensions being given. Concrete finishing is measured by the square foot or square yard of finished surface. After the “take off’’ has been completed, and the total yardage for each mix totaled, the quantities of cement, fine and coarse aggregates should be computed by means of the formulas given in Job 12 for computing quantities of materials for concrete. The following table gives the quantities of material required for some of the common mixes: MATERIALS REQUIRED FOR 1 Cu. Yb. or CONCRETE Coarse aggregate, cubic yards Fine aggregate, Cement sacks arc eaeda Mix by volume i NR a 10.50 0.39 0.78 1:114:3 7.64 0.425 0.85 Lite. 4 6.00 0.445 0.89 1:24%:5 4.94 0.46 0.915 i Nar e e3) 4.67 0.52 0.865 123295 °6 4.20 0.465 0.935 1 Fee: lp e . 3.23 0.48 0.96 156 CONCRETE PRACTICE To get cement in barrels, divide number of sacks by 4. The amount of water required will vary from 9 to 15 gal. per sack of cement, or from about 30 to 150 gal. per cu. yd. of con- crete, depending upon the water-cement ratio and the water used for washing mixer and equipment and wastage. About 100 gal. per cu. yd. of concrete is a good value for estimating purposes. The cost of materials delivered on the job is generally used, though on very large jobs the cost of cement will be the price at the mill plus costs of freight, unloading, trucking to job, storing, inspection and testing, and loss due to waste and spoiling. From the cost of cement in cloth sacks there should be deducted 10 cts. for each good cloth sack returned to the mill or dealer. As a general rule, about 10 per cent of the cloth sacks will be wasted. When the cement comes in bulk or in paper sacks, there will, of course, be no credit for returned sacks. Quotations of prices usually given by cement companies are for the cost of cement f. o. b. cars at the station near which the job is located. To this price must be added the cost of testing, unloading, and trucking. Average cost of cement (without sacks) will be from $2 to $3 per bbl. for large quantities, or $0.50 to $0.75 per sack. Assuming $0.65 per sack, or $2.60 per bbl., the cost of cement at the job will be about as follows: Cost oF CEMENT Item | Per sack | Per barrel Cement i. 0.:D) Carer te fess Se ee $0.65 $2.60 Gotton sacks: 67. si2. hens ea 0.10 0.40 Resting t)..20)idicnyd ae See ee eae 0.01 0.04 Unloading, trucking, and storing about......... 0.05 0.20 Total) é.c.a8 | overeating As i $0.81 $3.24 Credit for sacks returned less loss and freight... . . 0.09 0.36 Net: cost of. cement at jobeds &.. 2. 0i te. ee $0.72 $2.88 The cost of sand, gravel, and crushed rock at the job will vary greatly in different localities. The following are approximate prices only, and for relatively large quantities: ESTIMATING 157 Cost or AGGREGATE . Weight Per | price sey oa Price per Material cubic yard, cubic yard, dollars pounds dollars CEL adits 2700 1.10-2.50 1.50-3.40 oe gs Pacts eee or 2700 1.50-2.50 2.00-3.40 Crushed stone.............. 2500 1.80-3.00 2.25-3.75 The cost of water can best be found by finding the local rate per 1000 gal. and multiplying this rate by the number of thousand gallons required. In most localities there are also extra charges for setting the water meter and turning the water on and off. The amount of labor hours required to mix and place a cubic yard of concrete varies greatly according to the nature of the job and conditions of the work, kind of plant, and skill and inclination of the workers. The following are approximate values: Laspor REQUIRED TO Mrx AND PLACE CONCRETE Labor per cubic yard Kind of work of concrete in hours Gs a, Sw yo sb are cs we as wae es 3 to 6 ROTM CLINGS o.oo. ba ox le kee ee 4to7 COLES ADEN 0 A ene 2 to 5 Thin floors and pavements less than 5 in. thick .... 3 to 6 Thick floors and pavements more than 5 in. thick. . 2 to 5 RAG >... <...+,5 +s $0 .05 2 to 4 ft., Inclusive... so 5. ca oe $0.10 1 ft.to 1 ft. 11 in,, inclusive ...¢ 0.7.) Se 2 $0. 20 Under 1:ft.,; not less:than,.. ..4.<). 4,5 +. 2) bones eee $0.30 Steel bars in other than 1¢-in. sizes are rarely kept in stock by most dealers, hence the estimator and designer should not use 14 ,6-in. sizes. 7 Time In Hours REeQuirED FoR Maxine 100 E1cHTH or QUARTER BENDS Diameter of bar, Hand bending, Machine bending, inches hours - hours te -OVNOSS. “dia pe Eee 2.00—4.00 0.75-1.50 34 ANGRS iy cee eee 2.50—-5.00 1.00—2.00 Vesind [1Jeec. ay eee ae 3.25-6.00 1.25-2.50 14 iand 144 a Aw aes 4.00-7 .00 1.50-3 .00 TimE IN Hours REQUIRED FOR PLaciInG 100 Bars Length of bar Diameter of bar, inches Under 10 ft. | 10 to 20 ft. | 20 to 30 ft. Time required in hours +4 .0Y lees ce ae eee 3.5-6.0 5.0—- 7.0 6.0- 8.0 24 ONG Geo ae cart Eee ae 4.5-7.0 6.0— 8.5 1.0 9:5 Lean iid ie ee ee ee 5.5-8.0 7.0-10.0 8.5-11.5 T34 and 156 ee Bas ee eee 6.5-9.0 8.0-12.0 10.0-14.0 The bending and placing of steel reinforcement bars may be done by handy men at an hourly wage of from $0.50 to $1, under the direction of a competent foreman (wage $1 to $2 per hr.). In ESTIMATING 161 localities where union rules require a certain class of laborers, the wages of the laborers will probably be from $1 to $1.50 per hr. In regard to chairs, spacers, ties, etc., the total cost of these will vary greatly, depending on the kind used and the number required. An allowance of from $0.15 to $0.50 per 100 lb. of reinforcing bars is usually satisfactory. Exercises—Compute the weights and costs of the following reinforcing steel, using a base price of $3.65 per 100 Ib. Allow 35 cts. per 100 lb. for chairs and ties. Lineal feet Number of bars bize, ck rods 0-10 | 10-20] 20-30 | B°?28} 6-10 | 10-20 | 20-30 it: ie at fie ft. tt: Sen etTOUnd) es... 106 612 | 274 | None} 14 44 16 Peinei fount. ......1 318 948 0 86 42 66 0 34 in. (round)......... 462 | 894] 316| 56 | 57 | 52 | 28 Mean (round) ..:.....| 746.| 1264 836 12 96 74 38 41g in. (square)....:... ere ISOs) ware 12 e 14 ATC ECIIASE) 6 ob os ccs 5 ee 192 8 Me 12 3g in. (round) for spirals} ... ... | 2856 | None Compute the cost of bending and placing the steel, in the previous ques- ‘tion, assuming that all work is done by a gang of three handy men and a foreman. Foreman’s wage is $1.50 per hr., and wage of handy men is $0.85 per hr. The 2856 ft. of 3g-in. round bars for spirals will be assumed to be in 86 units, all bent in spiral form ready to be placed in column forms. No labor allowance need be made for placing the spirals in the column forms and tying them to the column rods, as this labor is included in the labor estimate for placing column rods. Allow 18 per cent for overhead. Compute the total cost of the steel of the previous two exercises all placed in forms. Allow 11 per cent for profit. Compute cost of steel per 100 lb. and per ton (of 2000 lb.) in forms. JOB 45. ESTIMATING FINISHING OF CONCRETE SURFACES The cost of finishing concrete surfaces varies according tothe price and quantity of materials used, kind of finish desired, labor hours required, labor wage per hour, and speed at which the men work. The following values are approximate and will vary greatly in different localities: 162 CONCRETE PRACTICE Labor, Cost, mons hours dollars Troweling floors, walls, sidewalks, etc. (100 sq. TO. ite Bato ee ee ees et i ae ee 2- 5 1.50— 5.00 Troweling plain base, cove, etc. (100 lin. ft.)..... 2-5 1.50— 5.00, Troweling fancy base, cove, etc. (100 lin. ft.).... 3— 6 2.00— 6.00 Carborundum rubbing of floor and wall surfaces (LOO eqs Ete tae kee Saleh Soe eee ene ene 4-10 3.00—-10.00 Carborundum rubbing of window sills, base, cove, ete-(L00 Lins ft.) ccs 0: aya perenne 4-10 3.00-10.00 Ornamental tooling (100 sq. ft:)......4..:.0.5- 8-16 6.00-15.00 1in. granolithic finish laid after concrete has hardened, including materials and labor (100 BQ ATO ais Clateae. Ws ce ae ene 7-12 7.00-14.00 1 in. granolithic finish laid integral with the con- crete, including materials and labor (100 sq. Tb) Sc ase BOE re alee es scala ag ea ee 4-8 5.00— 8.00 Scrubbing surface: 100/sq. it.) vans eee eee 2- 5 1.50— 4.00 Washing surface with acid (100 sq. ft.)......... 2- 5 1.50— 4.00 sand. blasting surface -(100 sq.ift,)s.... 3) eee 3— 5 2.25— 5.00 Cement surface wash per coat including materials (TOO WSC 1t..):,.c eas Woe es ceca eae 2- 5 2.50— 5.00 A 1-in. granolithic finish will require, per 100 sq. ft. of surface area, 1 to 1.25 bbl. of cement, and from 700 to 1000 lb. (about 7 to 10 cu. ft.) of aggregate. The aggregate may be part sand and part fine-crushed stone, or all fine-crushed stone with no sand. In concrete finish work, from 12 to 20 per cent must be added for various overhead expense. Exercises.—Estimate cost of finishing 1275 sq. ft. of surface by the fol- lowing methods: Labor hours Method per 10084 te Hourly wage Carborundum rubbing ABA etn Ro 6.20 $0.85 Omamentalstoolinge ene oe oe 10.50 $0.95 Washing with seid oe .e. 4 ee 3.40 $0.90 Allow 16.5 per cent for overhead and assume this figure to cover cost of materials. ESTIMATING 163 JOB 46. ESTIMATING MISCELLANEOUS ITEMS In the average concrete structure, there are frequently many items other than the excavation and the concrete work. Many of these items are given in the paragraphs which follow, together with their estimated costs. These cost estimates are approxi- mate only, and will vary greatly due to locality, material, wages, and efficiency of laborers. The approximate cost of brick work in place varies from about $30 to $75 per thousand brick. This includes cost of brick, mortar, labor, and scaffolding. Costs of laying vary from about $20 to $40 per thousand. In order to estimate the approximate number of brick, the following table is suitable for standard size brick (214 X 3% X 8 in.) laid with !4-in. joints: Estimated number of Thickness of wall brick per square foot of wall surface ae) 40.—1 standard brick width................. 7 $ in:—2 standard brick width................. 14 12% in.—3 standard brick width................. 21 17 in.—4 standard brick width................. 28 When estimating the number of brick, deductions for window and door openings are made only for about 50 per cent of their area, due to wastage of brick in cutting and fitting them around the openings. In estimating the labor, no deductions are made because of the extra labor in cutting, fitting, and laying the brick around these openings. The labor of laying a thousand of brick decreases with the thickness of the wall. Terra cotta partitions will vary in cost from $20 to $30 per 100 sq. ft. of wall surface. Concrete block masonry will cost from $45 to $75 per 100 block in the wall, assuming total labor and mortar costs of laying 100° blocks to vary from $8 to $15, and the blocks to cost from $35 to $60 per 100 delivered at the job. The average size of a block in the wall is about 16 in. long X 8 in. wide X 8 in. high. The 164 CONCRETE PRACTICE number of blocks of this size per 100 sq. ft. of wall surface will be about 115 (allowing a few for wastage) for an 8-in. wall. The cost of plastering will vary to some extent on the cost of materials, labor wages, and labor efficiency. On many jobs, the lathing and plastering are let as subcontracts. Item Cost per 100 sq. yd. Wood: lath in: place, 225) ois os ae $15 to $30 Metal lath ‘mn place i4.. 0%. 334 ee 20 to 40 Two-coat. plaster m placest.i.:.2) 4 Aas ) eee 30 to 60 Three-coat plaster*m place....... ...2. se eee 40 to 75 Hence the total cost of a two-coat plaster job on wood lath would vary from $45 to $90 per 100 sq. yd. Steel sash without glass cost from $30 to $50 per 100 sq. ft. of opening. Wood sash without glass cost from $15 to $30 per 100 sq. ft. of opening. With glass, the cost is $385 to $65 per 100 sq. ft. of opening. Glass and glazing cost from $20 to $35 per 100 sq. ft. Glass area 1s often assumed as 90 per cent of sash area. The cost of a single door and frame in place, complete with hardware, will vary from about $20 to $60. A pair of French doors with frame and hardware in place will cost from $75 to $125. Baseboards, molds, and other wood trim in place cost from $15 to $30 per 100 lin. ft. Tongue and grooved flooring in place will cost from about $18 to $30 per 100 sq. ft. of floor area. Rough flooring 1 in. thick will cost about half as much. No general estimate of cost can be made for light iron work and miscellaneous iron work. Flashing may be estimated at from $30 to $100 per 100 lin. ft. depending on kind and weight of material, copper flashing being the most expensive. Metal roofing in place will cost from $15 to $25 per sq. of 100 sq. ft. of roof surface for iron or tin, and about three times as ESTIMATING 165 much for copper. All metal flashing and roofing is usually let as a subcontract. A composition roof (tar and paper) covered with gravel will cost from $10 to $20 per 100 sq. ft. of roof surface. The cost of good composition shingles in place will vary from about $15 to $30 per 100 sq. ft. of roof surface. The cost of good wood shingles in place will cost from about $12 to $30 per 100 sq. ft. of roof surface. Cost of stucco per 100 sq. yd. varies greatly with the materials used, number of coats, thicknesses of coats, wood or metal lath, wages, and efficiency of labor. The cost of lath and stucco in place may vary from $50 to $125 per 100 sq. yd. The cost of painting varies greatly in regard to quality of paint, kind of surface to be covered, number of coats, wages, and efficiency of workmen. Average prices are from $1.50 to $3 per 100 sq. ft. for one coat. ‘Two-coat work will cost from $2.75 to $5.50 per 100 sq. ft. Cleaning up the job costs from about 149 of 1 per cent to 14 of 1 per cent of the total cost. Plans and specifications cost from 21% to 3 per cent of the total cost. Cost of inspection varies from 2 to 3 per cent of the total cost. Liability insurance varies from 5 to 10 per cent of the labor cost. Sundries vary from about 2 to 5 per cent of the total cost. General overhead expenses including office expenses, traveling expenses, job overhead superintendence, timekeeper, office clerks and stenographers, draftsmen, watchmen, telephones, freight, stationery, interest, insurance, etc., may vary from 10 to 20 per cent of total cost. Profit is usually estimated at from 8 to 15 per cent depending on the conditions governing the particular job. Such items as lathing and plastering, metal roofing and flashing and other metal work, heating, plumbing, lighting, painting, etc. are frequently let as subcontracts. Plumbing fixtures cost from $60 to $100 per fixture, heating from $75 to $125 per radiator for steam and hot-water heat, and from $50 to $75 per hot air register for hot air heat, lighting from about $5 to $12 per drop or light outlet with fixtures extra. 166 CONCRETE PRACTICE Summarizing, the items of cost of a concrete structure to the owner may be listed as follows. Architect’s fees and commission. Main contract, including excavation, forms, concrete, steel, finish, cleaning up, sundries, overhead, and profit. Subcontracts—if let separately. Extras. Land, including proving of title, etc. Interest and insurance during construction. Cost of financing. Profit to owner, if he sells. Exercises.—On what items does the cost of brick work depend? What items are usually let as subcontracts in concrete building construc- tion? Which wall would be cheaper: an 8-in. brick wall with brick costing $28 per thousand and complete labor and mortar costs of laying brick in wall of $34 per thousand, or an 8-in. concrete block wall made with blocks about 8 X 8 X 16 in. in size and costing 45 cts. each on the job, and complete labor and mortar costs of laying block in the wall of $12 per 100 blocks? JOB 47. SQUARE AND CUBE METHODS OF ESTIMATING BUILDING COSTS While the only safe and sure means of estimating is to take off actual quantities of materials and hours of labor, and use the local unit prices prevailing in order to determine the total cost of the structure, many experienced estimators use the approximate methods of estimating certain types of structures by the cube or square, in order to obtain approximate costs in a short time, and also as a comparison and rough check on the costs found by the more accurate methods. The method of estimating by the square of 100 sq. ft. or 1 sq. ft. of floor area is applicable to office buildings, schools, mills, warehouses, factories, hospitals, churches, stores, residences, and garages. This method is useful in comparing the costs of different buildings, where the floor area is important, as in offices and factories, and in determining the capacities and costs per person, as in schools, churches, and hospitals. There are several variations in estimating buildings by the square. One method is to allow a certain figure per square foot for each floor, and use other figures for the roof and foundation ESTIMATING 167 areas. Another method is to use different unit prices for the different floors—the lower floor to include cost of foundations, and the upper floor to include cost of roof. A third method is to use the same unit price per square foot of floor area for all floors, omitting the roof area or both the roof and basement areas. The method of estimating building costs by the cube or volume is more accurate, in general, than the method of estimating by the square. The best method of estimating by the cube is to find the total volume of the building in cubic feet, and multiply this volume by a selected unit price per cubic foot for this particu- lar class of building. Another method is to use a certain unit cost per cubic foot for the part of the building that is more expensively finished, and another price for the portions that are more cheaply or less completely finished. For example, in a residence, the cubic contents of the basement, attic, and garage would have one unit price, and the living-room, dining-room, kitchen, halls, bath, and bedrooms would have another unit price. A third method is to consider only half or two-thirds of the volume of the basement, attic, and garage, when computing the cubic contents of a residence, and then use the same price per cubic foot for all parts of the building. Of course, buildings of different types and kinds of construction would require different unit prices per cubic foot. | Exerctses.—A certain building is 40 X 60 ft. in size and consists of base- ment, first, second, and third floors, and attic. Assume heights (including floor thickness) of 8.5, 10, 9, and 9 ft. for basement and the first, second, and third floors, respectively, and an average height of 7.5 ft. for the attic. Cost of building was $44,270. Compute the cost per square foot by each of the following methods: 1. Based on the floor area of the three floors. 2. Based on total area of three floors, basement, and roof, assuming roof area equal to one floor area. . 3. Based on area of three floors and basement. 4. Based on area of three floors, assuming that the cost of the first floor is 1.60 times the cost of the second, and that the cost of the third floor is 1.50 times the cost of the second. Compute the cost per cubic foot by each of the following methods: 5. Based on the total volume of the building in cubic feet. 6. Allowing full value for the three stories, 60 per cent of the value for the basement, and 50 per cent of the value for the attic. Note.—Take cubic feet for the three stories, and add 60 per cent of the cubic feet in the basement and 50 per cent of the cubic feet in the attic. 168 te CONCRETE PRACTICE JOB 48. SAMPLE QUANTITY ESTIMATE FOR CONCRETE WORK In this job, a sample quantity estimate will be made of the materials and labor required for the reinforced concrete slab shown in Fig. 71, page 140. It will be assumed that the estimates have been previously prepared for the abutments. The estimate will be divided into four parts: forms, steel, concrete, and surface finish. A “‘take off” of the quantities will be made first, and then an estimate of the labor will be given. It is to be remembered, that all labor estimates are approximate only. Forms. Under side of floor slab = 30 X 16 = 480 sq. ft. Ends of floor slab (allowing for pavement notch) = 2 30 X 15 = 75 sq-it: Sides of floor slab = 2 X 16 X 2 = 64 gq. ft. Railings, two rails, sides and ends =(2X2xX3xX19 +2X2xX 3X DiS | 240 sq. ft. Total square feet of form surface = 480 + 75 + 64 + 240 = 859 sq. ft. In determining the number of board feet required per 100 sq. ft. of form surface, it should be noted that the form lumber must be of selected lumber carefully fitted together and rigidly braced. This means that there will be considerable wastage even under the most favorable conditions. The shoring for the slab, and the paneling of the railing will require considerable lumber. An allowance of 525 bd. ft. of lumber will be made for each 100 sq. ft. of form surface for this estimate. This can be checked, when a bill of materials is made for the form lumber. 525 & 859 "0. ae 4500 bd. ft. of lumber. ah} Allowing 1.5 lb. of nails and bolts per 100 sq. ft. of form surface gives 1.5 X 8.59 = 13 lb. nails and bolts. The hours of labor required per 100 sq. ft. of form surface will be comparatively large, due to the care with which the forming must be done. For this estimate, 12.5 labor hr. per 100 sq. ft. of forms will be assumed for assembling and erecting, and 3.5 Total lumber for forms will be ESTIMATING 169 labor hr. per 100 sq. ft. of form surface for stripping and cleaning forms. Labor hours for forms = | (12.5 + 3.5) X 85999 = 187.5 labor hr. Concrete Materials——The number of cubic yards of concrete required is given in Fig. 71 as 27.5 cu. yd. A check will be made of this quantity as follows: Floor slab sae or OU x 1125 =O UHLCUS LL Rails eee 11) XU. ooo 15.0 4 L115 cu, ft. Curb eee 0.70) U.00ExX 18.0, = 14 eu: it: Total 754 cu. ft. Deduction for pavement notch Bee o8T x 1 xX 0.88 = is CU site Net concrete PAOCCUL al Gee = 27.3 cu. yd. There is no allowance here for wastage or possible slight over- run. Will use 27.5 cu. yd. in estimating materials, and add about 5 per cent for wastage. Materials required for 27.5 cu. yd. of Class A concrete of 1:2:4 mix, are: Sacks of cement 27.5 X 42 es 4 = 165 sacks, assume 168 Cubic yards of sand pee el DOT 2 = "eg a 12.2 cu. yd., assume 13 Cubic yards of stone or gravel Beat.0 XX 1.00-x< 4 — j1+2+4+4 The water required will be approximately 2750 gal. The values assumed allow for about 5 per cent wastage. The wastage of aggregates will usually be a little more than that of cement. The labor hours required to mix and place concrete in a bridge will be comparatively high, possibly from 4 to 7 hr. per cu. yd. of concrete. The roadway surface must be finished as it is laid. = 24.4 cu. yd., assume 26 170 CONCRETE PRACTICE For this job, 5.5 hr. of labor per cu. yd. of concrete will be assumed. ‘Total labor hours required for mixing and ee concrete will be 5.5 X 27.5, or 151 hr. Consideration of the concrete plant will be made in the cost estimate. The plant and crew must be large enough, so that all of the concrete for the slab bridge, except railings, can be placed inl day. eee at $1.95 per cu. yd. = 25 ee i peg 26 cuceyd. stone, 400.) eee at $2.20 per cu. yd. = 57 Wateriina. 2s cee ee eee 5 Tabor LS] chr 8s wae ee at $0.60 per hr. = 91 Plant estimated .9..06c% <6. s0ls 6 50:0 0 nite ae Paeue eee ane ae 40 Total for concrete. 0.0.6.5 ies 3 oo 2 eee $331 Mnighing labor... ..ece ee O4 DATS ann Giese eee at $0.60 per hr. = $57 Superintendence and overhead....5 <6. oc ose «sew o> oo ones eee iene na anne ae een eee $125 Profitea cc ci scaw oie 6 ceo. cb 0 6/8 6 oa ube Hiv leks’ ows eee Yen as a) eee oneal See ene een an $110 Total bid oo 0es eo nc ed ne ewe ola tuna a cle e Eels a $996 Cost per cubic yard, 2755 cu. yds. 6 oak ues vic oo eines oie ee $ 36.50 Exercises —What would the total cost estimate for the reinforced concrete slab bridge have been if: Lumber cost $39 per thousand with a salvage value of $12 per thousand Steel cost $0.0352 per lb. delivered on the job. Cement cost $2.75 per bbl. delivered on the job. Sand cost $2.05 per cu. yd. delivered on the job. Good gravel cost $1.90 per cu. yd. delivered on the job. Overhead and superintendence cost 17 per cent. Profit is estimated at 10 per cent. Other prices the same. Also compute cost of concrete per cubic yard in the completed job. ESTIMATING 173 JOB 50. TIME AND WORK SCHEDULES FOR CONCRETE JOBS On medium-sized and large concrete jobs, it is advisable to provide time and work schedules for the convenience of the main office, superintendent, and foremen. Such a schedule notes the different construction operations, the estimated dates that each operation should start and finish, and the actual dates. Such a schedule, together with progress reports and charts (if the job is a large one), enables the contractor or engineer to note if the work is progressing as planned, and to observe which items are ahead or behind the schedule. Certain construction operations and trades should follow each other in regular order and without interference. Confusion, with a resulting loss of efficient work, often occurs, when two comparatively large gangs are scheduled to work on the same part of ajob at the same time. Two small gangs may frequently work on the job at the same time (such as plumbers and electricians doing rough plumbing and wiring in a residence), without inter- ference. In general, the paint gang should come last (except for priming coat work) on any section of the job, and after the other gangs have completed their work. It is not necessary for any one operation to be wholly com- pleted before another operation is started, but the work should be so planned that the different operations do not interfere with each other. For instance, on concrete paving work, the excava- tion gang should be about a half a day or so in advance of the roller, and the concreting gang should follow about a day behind the roller. This allows the work to go forward efficiently, pre- vents interference between gangs, and permits the general superintendent or contractor to speed up any gang that is lagging. In order to note if the work is progressing according to schedule it is usually required that the superintendent, general foreman, inspectors, or timekeepers (depending on to whom the duty is assigned) make a daily report or record of the different kinds and quantities of work done. In addition to making the daily reports or records, a daily diary should be kept by the proper official in which all essentials relating to the particular job are noted. In general, the superintendent or general foreman is the best person for preparing and signing the daily reports. 174 CONCRETE PRACTICE The following schedule is for the work on a garage building: TIME AND WorRK SCHEDULE Type of Building Garage Location 2463, 1st St. Supt. Estimated Actual Num- dates dates Item ber Start | Finish | Start | Finish Bend and place steel........... Mix and place concrete........ Remove lors oie Uae tee Sash, frames, and trim......... Glass and: glazings. .cV ane: Roofing and eee REA SE aL Plumbing. ere mr ee ey Cleaning up av anae oe eee Paintings aces © ci ee ee Schedule time of completion.... Contract time of completion.... a a ae ae IOoorrwnrnrFPoowonraoamnrwnd On a one-course concrete paving job, the time and work schedule would include the following items: excavation, rolling . subgrade, forming, concreting and finishing, curing, removing forms and cleaning up, finishing shoulders, scheduled time for completion, contract time for completion. On large jobs, delivery schedules are often provided for all of the materials used, so that there will be no delays due to lack of materials, and, at the same time, there will not be a surplus of materials to cover up the work. Labor schedules are sometimes made showing the numbers of each of the different classes of laborers required on the job for each day. Exercises.—State advantages of a time and work schedule for a concrete job. Prepare a time and work schedule for constructing 1900 lin. ft. of 5-ft. concrete sidewalk. All of the walk (slight excavation, forming, and con- creting), except curing, must be completed in 5 weeks’ time. State assumed dates for schedule time. Excavation work to start on May 1. ESTIMATING 175 JOB 51. PROGRESS REPORTS AND CHARTS The superintendent or foreman on a concrete construction job should send in to the main office every day a detailed report of the progress of the work in his charge. By this method, the MATERIALS RECEIVED AND WORK DONE ee ee eee COC ALON err one SUPERINTENDENT MATERIA Se GES ey ol Cl eS (5 ¢ fo (Sa ae Gravel, (cuyds,) 1 ee Stone, (pounds) |__| Lumber, (Soard ft) Nails €Bolts,//os) |__| Other Items LABORERS] HOURS FORMS STEEL see EEE CLEANED STRIP | AND REP'D. CONCRETE CLEAN UP OF JOB Y WW ° Mix | PLACE] FINISH S Ze ] 2 3 4 5 6 7 8 Gell nee aa ge bal [ad ee ie] at pol CEEUBELE Ponrmamesemoea = = Sq.ft. See SOIL Forms stripped ______—=>=—=———SSs.ft.] Forms cleaned € repd. sq. ft. Steel bent fee 105,,| Steelipiaced pee IDS, Concrete mixed and placed ____cu.yd.| Concrete surface finished. sq. ft. Other work Fig. 73.—Superintendents’ daily report form. main office is enabled to keep in close touch with the job, and to take any needed steps in regard to the supply of materials and labor. An examination of the progress reports will show whether 176 CONCRETE PRACTICE the work is progressing at a satisfactory rate in regard to quanti- ties and costs. Figure 73 shows a sample form of daily report required from the superintendent on a concrete job. This report gives a complete summary of materials on hand, received, and used, laborers and their work, and the amount of work of different kinds performed. The daily reports of the superintendent or foreman should be checked from time to time by the timekeeper or other official, to provide against possible dishonesty and errors. PROGRESS CHART FOR CONCRETE WORK Estimated| Actual | Percent | 9 = “Concrete ieaease Time | Time | of Work Estd.Cost olf May 29 | 108 2000 | $29000 “fen ~~ \ ~~ ~~ ao aS Q SSS see BS Soe eee eseees SKS Reet cee ~~ oa seanetoneennnseee SPSS \ recone Fic. 74.—Progress chart for concrete work. So that the owner, contractor, architect, or engineer may clearly and easily visualize the amount of work done, rate of prog- ress of the job, and the cost of the work, progress charts are prepared and kept up to date. A progress chart is a graphical representation of the progress of the work on the job i in question. These charts are prepared from the data given in the progress reports and must be kept up to date. A progress chart may be simple or complicated, and show a few or many details, as the case may be. The charts should not be too complicated, or contain too much detail, if they are to be read and understood by the average person. | ESTIMATING Livi A simple progress chart for concrete work is shown in Fig. 74. The chart includes estimated time, actual time, per cent of work, cubic yards of concrete, estimated cost, and actual cost. On this one particular job, note that the work lagged for the first 2 weeks while the costs were greater than were estimated. During the last 2 weeks, the work was speeded up and the job finished on time, with an actual cost a little less than that estimated, in spite of the fact that the actual concrete required in cubic yards exceeded the estimated amount by 5 per cent. - Figure 75 shows a time-work schedule for a concrete construc- tion job involving excavation, assembling and erecting forms, JOB S74... TIME-WORK SCHEDULE — JUNE an eae a Excavation ee recting Forms g ean mel Bending and ae) SULLA ies eee UMMLML A: Placing Steel Mixing and —--] UUtttb ee Placi = Concrete -—| | = = rms eo pies Wlttte need 7ime "ease eee VLIMTLLLEA a inishing ctual Time | Fig. 75.—Progress chart and time-work schedule. bending and placing steel, mixing and placing concrete, form removal, and surface finishing. The open (or white lines) show the estimated time, and the full black lines show the actual time required. This chart could be lengthened and elaborated to include as many operations as desired. Another version of this chart is to plot the time required with vertical lines, and plot the operations horizontally. In Fig. 76, the same data were plotted as in Fig. 75, but are shown in a different manner. The light lines indicate the estimated time, while the actual time is shown by the heavy lines. Note that the actual excavation exceeded the estimated quantity (due to a bank cave in), while the other actual quanti- ties agreed with the estimates. In regard to the time required, 178 CONCRETE PRACTICE the excavation, form removal, and surface finishing each required a longer time than was estimated, while the erection of forms and steel placing each required less time. Another variation of the chart shown in Fig. 76 is to use a light black line showing the relation between estimated time and quantity of work in percentages, a heavy black line showing actual time required, and a heavy red line for costs. If, for any operation, the red (cost) line agrees with the heavy black line, TIME-WORK SCHEDULE JOB./74... | 75 Per Cent LEGEND Light Lines= Estimated Time HeavyLines= Actual Time Fig. 76.—Progress chart and time-work schedule. the estimated and actual costs agree; if the heavy red line is below the heavy black line, the costs are less than were estimated; while, if the red line goes above the heavy black line, the costs are more than were estimated for the corresponding quantity of work. Note that the quantity of work and costs will be expressed in the form of a percentage of the estimated total of each. Actual quantities and costs may be written on the chart adjacent to the corresponding points on the lines, if desired. Exercises.—Prepare a progress chart showing the following data in a concrete road job: Excavation, estimated 12,000 cu. yd., cost $1.25 per cu. yd., start Aug. 1, finish Aug. 29. ESTIMATING 179 Forming at sides of road, estimated 11,320 lin. ft., cost 10 cts. per lin. ft., start Aug. 3, finish Sept. 38. Steel forms are used and reused throughout the job. Concrete, estimated 1885 cu. yd., cost $12.85 per cu. yd., start Aug. 4, finish Sept. 4. Progress Reports—totals are given. Excavation, start Aug.1; Aug. 8, 2750 cu. yd., cost $3680; Aug. 15, 5450 cu. yd., cost $7025; Aug. 22, 8725 cu. yd., cost $11,100; Aug. 29, 11,200 cu. * yd., cost $13,900; Sept. 1, finish, 12,320 cu. yd. cost $15,200. Forming at sides, start Aug. 4; Aug. 8, 1420 ft. cost $151; Aug. 15, 3230 ft., cost $347; Aug. 22, 6170 ft., cost $628; Aug. 29, 9250 ft., cost $930; Sept. 3 finish, 11,320 ft., cost $1116. Concreting, start Aug. 5; Aug. 8, 228 cu. yd., cost $8030; Aug. 15, 531 cu. yd., cost $6950; Aug. 22, 1020 cu. yd., cost $13,420; Aug. 29, 1530 cu. yd., cost. $19,600; Sept. 4, finish, 1891 cu. yd., cost $24,150. SECTION V LABORATORY METHODS WORK IN THE LABORATORY Purpose of Laboratory Work.—The purpose of this labora- tory work is to give the student a general idea of the physical properties of cements, aggregates, mortars, and concretes, and the various ways of testing them. The student is not expected to become an expert tester upon the completion of the course, but he will be expected to know how the different tests should be made. Considerable experience is necessary before anyone can become an expert in the testing of cements and concretes, and in the correct interpretation of the results. It is only by close observations of the rules and specifications that even this may be accomplished. Apparatus.—Each student will be held responsible for all apparatus assigned to him. In general, all apparatus needed during the laboratory period should be secured from the instruc- tor at the beginning of the period. All tools, apparatus, tables, etc., should be cleaned immediately after using, and all of the waste material should be deposited in the waste boxes provided for that purpose. Waste material should not be thrown on the floor. Neatness and cleanliness are important elements in all laboratory work. Making Specimens.—The methods of mixing and molding given in the standard methods and specifications will be followed in all tests as far as practicable. At the beginning of the first laboratory class, the instructor should illustrate the methods of preparing briquette molds and the mixing and molding of briquettes. Curing Specimens.—All cement, mortar, and concrete speci- mens will be removed from the molds, marked, and stored accord- ing to the requirements of the standard specifications. 180 LABORATORY METHODS 181 Marking Specimens.—Each specimen, at the time it is made, or when it is removed from the molds, should be marked, so that it can be identified as to owner, composition, and test. Bri- quettes should always be marked on the ends. When in doubt, consult the instructor in regard to the proper way of marking the specimens. Testing.—A student must not use any machine until its prin- ciples of operation have been explained to him by the instructor. A good rule for the student is: Do not use any testing machine _ unless the instructor is present and has given permission. In testing, follow the instructions given in the job sheets and in the standard methods and specifications. Good results can be secured only when the rules governing the operation of the testing machine are strictly followed. Notebook.—Each student should keep a notebook for use in the laboratory. In this notebook, the student should record the date of making, composition, and marks of the specimens, the dates on which the specimens are to be tested, the data obtained during the tests, and all other observations and data that may be of usein writing reports or in making future experiments. Efficiency.—In the laboratory students should: (1) try to do ’ good work, and (2) try to do the work in as short a time as prac- ticable. That is, students should try to become both good workers and fast workers. ‘The instructor may, at various times, instruct students in their work so that their efficiency will be improved. LABORATORY REPORTS Laboratory Reports.—The laboratory reports required may be written either in a laboratory report book or on loose sheets of typewriter-size paper, and the sheets comprising each report fastened together with clips. If report books are used, the paper in them should preferably be cross-section paper, of about 5 divisions per inch. If loose sheets are used, it is advisable to fasten the sheets inside manila folders. The front cover page of this folder should have on it the title of the test, the student’s name, the date that the report is due, and any other information - required by the instructor. All reports should be neatly written in ink or typed. 182 CONCRETE PRACTICE Outline.—The standard outline for a laboratory report is as follows: 1. Title 6. Computations 2. Object 7. Curves 3. Apparatus (and sketches) 8. Conclusions 4. Method 9. Answers to questions 5. Data Title-—The title should indicate the subject of the experiment or test. In general, the heading given the experiment on the job sheet will be sufficient. Object.—This is a brief, concise statement of the purpose of the experiment. . Apparatus.—Under this heading include a list of apparatus used and, when required, a neat sketch of some piece of the apparatus. Any. special apparatus used should be briefly described. Method.—Describe briefly how the test was made. If the method is a standard one that has been described in the text, a reference to the text (giving the page number) will be sufficient. Data.—The data should be tabulated in a neat systematic form. All data should be carefully checked before handing in the report. ; Computations —Sample computations should be included in the report, to show how the main results were obtained from the data. The formulas used and the numerical substitutions in them should always be given in full. Results of computations should be accurate to 1 per cent. The properties of the specimens tested will rarely be the same as the average properties given in the texts. Results differing greatly from the average values frequently indicate errors in computations. Curves.—Curves should be drawn on cross-section paper of the same size as the report paper, and having 5, 10, or 20 divisions perlinealinch. ‘The points determining the curve should be shown in small circles (small triangles, squares, etc., may be used, if there be more than one curve). The curve should be carefully drawn with either a straight or a curved ruler. Medium and fine lines are better than heavy ones. When there are only a few points, LABORATORY METHODS 183 straight lines should be drawn connecting these points; but when there are many points, a smooth curve should be drawn. The scales of the coordinates should be plainly marked. The curve sheet should show the title of the experiment and the main results. Conclusions.—The conclusions should contain a summary of the main results and important facts obtained from the test. Questions.—All questions asked should be answered in full. JOB 52. INSPECTION AND SAMPLING OF PORTLAND CEMENT Object.—To inspect and sample a shipment of portland cement. Significance—The securing of a representative sample of cement is essential, if the test results are to indicate correctly the properties of the cement. References.—Appendix 1. Inspection.—Observe if the shipment is stored in such a manner that it can be easily inspected and identified, and also observe if the building is weather-tight, and the cement protected from dampness. The cement may be in bulk, barrels, or bags. If in barrels or bags, note if the brand of the cement and the name of the manufacturer are plainly marked thereon. , ~Check the weights of several bags (or barrels), and note if the weight requirements of the specifications are met. Observe if the cement contains lumps, and if the lumps are hard or soft. Soft lumps are comparatively harmless. Sampling.—Secure a sample as directed in Secs. 16 to 19, inclusive, of Appendix 1. If the cement is sacked, a sample may be obtained by inserting a piece of split tubing through a flap in the bottom of a sack. Metal cans with tight covers or heavy paper sacks are suitable containers for cement samples. The container should be marked so that the sample can be correctly identified. Report.—Prepare a brief report. This report should include the name of the brand and the manufacturer of the cement, size of shipment (approximate or actual number of bags or barrels), the place of storage, the name of the inspector, the date of the inspection, the results of the inspection as to proper storage, lumps, weights of barrels or bags, etc., whether the sample was an 184 CONCRETE PRACTICE individual or composite one, size or weight of the sample, the marking on the container of the sample, and any other informa- tion that the inspector deems essential. JOB 58. NORMAL CONSISTENCY OF PORTLAND CEMENT Object—To determine the percentage of water required to make a cement paste of normal consistency. Significance.—The correct percentages of water must be used when mixing the neat cement pastes and the cement mortars, or the test results will not be reliable. References—Appendix 1. Materials —Portland cement. Note the brand. Apparatus.—Scales, trowel, graduated cylinder for measuring water, watch, Vicat apparatus, etc. Vicat Method.—¥Follow method given in Sec. 39 of Appendix 1. Use about 23 per cent of water for the first trial paste. Record penetration of rod. If this paste is not of normal consistency, make other trial pastes with varying percentages of water until the normal consistency is obtained. Ball Method. (Old U.S. Government Method).—After mixing a trial paste by the previously described method, quickly form a 2-in. ball of the neat cement paste. Drop the ball, from a height of 2 ft., upon the table top. The cement paste is of nor- mal consistency when the ball does not crack and does not flatten more than one-half of its original diameter. Make trial pastes with varying percentages of water until the normal consistency is obtained. Notr.—When a trial paste of normal sonst has been obtained, this paste may also be used for determining the time of set and for making the pats for the soundness test. Report.—Prepare a tabulation showing the percentages of water used, and the corresponding penetrations of the Vicat rod or the corresponding flattenings of the diameter (expressed approximately in tenths of the original diameter) in the ball test. Note the mixtures which cracked when they were dropped 1 in the ball test. Questions.—If both methods were used, which method gave the best results? Why? LABORATORY METHODS 185 How will the amount of water in the trial paste affect the strength and setting time of the cement? | Why do different cements require different percentages of water to give normal consistency? The quantity of cement to be mixed at one time should not be less than 5000 g. or more than 1000 g. Why? JOB 54. TIME OF SETTING FOR PORTLAND CEMENT Object—To determine the time required for initial and final’ set of a sample of portland cement. Significance.—The object of this job is to determine the time which elapses from the moment water is added until the paste ceases to be plastic (called the initial set), and also the time which elapses before the paste acquires a certain degree of hardness (called the final set or hard set). The former is the more impor- tant, since, with the commencement of setting, the process of crystallization begins. As a disturbance of this process may cause a loss of strength, it is desirable to complete the operation of mixing, molding, or incorporating the mortar or concrete into the work before the initial set occurs. References.—Appendix 1, and See. I. Materials —Portland cement. Note the brand. Apparatus.—Vicat apparatus or Gillmore needles and other apparatus, as in the preceding job. Method.—Follow the directions given in Sec. 45 to 49 inclusive of Appendix 1. Either the Vicat apparatus or the Gillmore needles may be used for determining the time of set. Be sure to note the time when the water was first added to the cement. Report.—Note the time required for the initial and final sets of this sample of portland cement. Questions.—Did this sample of portland cement pass the specifications for the time of setting for portland cement? Which method of test (Vicat or Gillmore) do you prefer? Why? What is the effect on construction work of using a quick-setting cement? Of using a slow-setting cement? If a cement having a flash set is used in concrete, how should this concrete be mixed to overcome the effect of the flash set? 186 CONCRETE PRACTICE JOB 55. SOUNDNESS TEST OF PORTLAND CEMENT Object.—To determine the soundness of a sample of portland’ cement. Significance.—Portland cement must be sound (that is, must not swell, disintegrate, or crumble) if it is to be used on construc- tion work. The steam test quickly brings out those qualities which tend to destroy the strength and durability of the cement. References—Appendix 1 and Sec. I. Materials —Portland cement. Note the brand. Apparatus.—Scales, graduated glass cylinder for measuring water, trowel, watch, glass plates about 4 in. square, and the special apparatus for the steam test,etc. See Fig. 3 of Appendix 1 for an illustration of this special steam test apparatus. Method.—Follow the method given in Secs. 42, 48, and 44 of Appendix 1. Note that it takes some practice and skill to make a good, smooth, neat cement pat of the correct size and shape. Testing.—After the water is boiling in the steam test apparatus, place the day-old pat in the apparatus, as directed in Sec. 43 of Appendix 1, and keep the pat there for 5 hrs. Report.—State the results obtained from the test. Questions.—Did this sample of portland cement pass the sound- ness test specifications? Why should the pat have thin edges? Is the cement sound if the bottom surface of the pat is found to be curved or warped after the conclusion of the steam test? Does the passing of the soundness test always indicate a sound cement? JOB 56. STANDARD TENSION TEST Object—To determine the tensile strength of the standard portland cement mortar. | Significance—Tensile tests on the standard mortar give a fairly good indication of the strength qualities of a portland cement. References.—Appendix 1 and Sec. I. Materials—Portland cement and standard Ottawa sand. Note the brand of the cement. Apparatus.—Two 3-gang briquette molds, scales, graduated glass cylinder, trowel, watch, etc. LABORATORY METHODS 187 Method.—Follow the method given in Secs. 36, 37, and 50 to 61, inclusive, of Appendix 1. Make six briquettes of 1:3 mortar (1 part of cement to 3 parts of sand by weight). About 250 g. of cement and 750 g. of sand are required for six briquettes. Obtain the percentage of water from Table 1 of Appendix 1. The amount of water needed is found by multiplying the total weight of the cement and sand by the percentage given in the table. Storage.—One day in moist air and then in water as directed in Appendix 1. Testing.—Break three briquettes at an age of 7 days, and the remaining three at an age of 28 days. Record results. Reports.—Tabulate the individual and average results at each age, together with the brand of cement, percentage of water, etc. Questions —Did this sample of portland cement pass the standard specifications for strength tests? Does the amount of water used in making standard mortar briquettes affect their strength? Why should the mortar be thoroughly mixed? What is the area of the smallest cross-section of a briquette? How would storage in air affect the strength of the briquettes? - JOB 57. FINENESS OF PORTLAND CEMENT Object—To determine the fineness of a sample of portland cement. Significance.—The extremely fine powder or flour in portland cement is the important cementing element. As there are no sieves fine enough to determine satisfactorily the percentage of this flour, the fineness test only tends to indicate the soundness and strength of the cement. Usually a coarse cement will show a low mortar strength, and will often fail to pass the soundness test. References—Appendix 1 and Sec. I. Materials.—Portland cement. Note the brand. Apparatus.—Standard 200-mesh fineness sieve with cover and bottom, and scales sensitive to about 0.01 g. Method.—Follow the method given in Appendix 1. The scales should be leveled in a place where they will not be affected by 188 CONCRETE PRACTICE air currents. Results should be noted to the nearest tenth of 1 per cent (nearest 0.05 g.). Report.—State the results obtained. Question.—Did this sample of portland cement pass the stand- ard specifications for fineness of cement? If the same sample of portland cement was used in Jobs 52 to 57, inclusive, and if the soundness, set, tensile strength, and fineness tests only were required, would this portland cement be considered as satisfactory for use'in concrete for construction purposes ? Norr.—Jobs 52 to 57, inclusive, include all of the tests that are usually asked for when testing a sample of portland cement. In some instances, the fineness test is omitted. JOB 58. INSPECTION AND SAMPLING OF AGGREGATES Object.—To inspect a source of supply for concrete aggregates, and to secure samples. Significance—Before beginning any large concrete job it is important that the engineer should know about the aggregates to be used, especially in regard to quantity, uniformity of supply, grading, and other qualities. References.—Sec. I. Method.—The following information should be obtained in regard to all stone quarries or gravel pits inspected: name of owner, locality, approximate quantity available, character of overburden or stripping, length and character of haul to the job, or to the shipping point. Crushed Stone from Commercial Quarries.—In addition to the above information, data should be recorded concerning the crushing and screening plant, such as number and size of crushers, size and shape of screen openings, daily capacity of plant, number and size of storage bins, and sizes of crushed stone sold. When practical, samples of fresh, unweathered rock may be taken from the quarry face. Samples of crushed rock may be taken from the stock piles, bins, loading chutes, cars, or boats. It is advisable to take the samples from the cars or boats while they are being loaded—the samples being taken at different times and then well mixed to make a composite sample. If samples are taken while the cars or boats are being unloaded, samples should be obtained LABORATORY METHODS 189 from the top, middle, and bottom of each car or boat. The weight of the sample of crushed rock should be from 50 to 100 lb. Sand and Gravel.—Very few sand and gravel deposits are uni- form throughout, hence it is often necessary to take separate samples from several parts of the pit, if correct information in regard to the bank run is to be obtained. Note if any of the top soil has fallen into the pit, if there is any clay in the pit, and if there are pockets of fine or coarse material. In pits where there are screening and washing plants, the samples should be secured from the tops and the loading chutes of the bins, care being taken to obtain representative samples. If it is not practical to visit the pit or plant, samples may be taken from the top, middle, and bottom of the car or boat when unloading. Samples of bank-run gravel should be 100 lb. or more (the sample should provide at least 50 lb. of gravel after screening). Samples of gravel should contain at least 50 lb., and samples of sand at least 20 Ib. A sample should be placed in a tight box or bag; and should be carefully tagged, so that it can be identified. It is a good plan to place an extra marked tag inside of the container. Quartering Method.—All samples should be brought to the laboratory for observation and testing. If any sample is too large, it may be reduced in size by the quartering method. The- sample should be first thoroughly mixed on a tight platform or floor, and then spread into a circular pile and divided into four parts or quarters. Two of the opposite quarters are shoveled away, and the process of mixing and quartering repeated until the sample is reduced to the desired size. Report.—Write a brief report describing the crushed stone or gravel plant visited. A complete investigation would also include reports of the tests made on the samples such as sieve analyses, silt test, colorimetric test, and, when time permits, strength tests of concrete made from the aggregates. JOB 59. UNIT WEIGHT OF CONCRETE AGGREGATES Object—To determine the weight per cubic foot of fine and coarse concrete aggregates. Significance—When designing concrete mixes by Beetle methods, it is necessary to know the unit weights of the aggre- 190 CONCRETE PRACTICE gates, so that the proportions of the concrete mixes may be correctly computed. References —Appendix 2 and See. I. Materials—Room-dry samples of both fine and coarse aggre- gates. Apparatus.—Tamping rods and metal measures described in Appendix 2. If these measures are not available, strong and tight wooden boxes of 14 cu. ft. and 1 cu. ft. capacity will usually prove to be satisfactory. Method.—Follow the method given in Appendix 2. After the unit weight has been found for a room-dry sand, thoroughly dampen this sand by adding 5 per cent of water by weight, and then mix the sand and water. Then determine the unit weight of the dampened sand. Report—Make a tabulation showing the various materials tested, and the resulting weights per cubic foot. Questions.—Does the dampened sand weigh more or less than the dry sand? Why? If the proportions for a concrete mix were based on dry sand, what would be the effect on these proportions of using damp sand? JOB 60. SIEVE ANALYSIS OF AGGREGATES Object—To make sieve analyses of various fine and coarse aggregates. Significance.—As several of the methods of proportioning concrete mixes depend upon the grading of the aggregates, it is necessary first to make sieve analyses of the aggregates. References.—Appendix 8 and Sec. I. Materials—Samples of different fine and coarse aggregates which are room dry. Apparatus.—Scales which are sensitive to about 14 g., and a set of standard sieves as described in Appendix 3. These sieves are practically the same as the Tyler series of sieves, in which the opening of any sieve is double that of the next lower sieve. Method.—Follow the method outlined in Appendix 3. If there is any doubt about a sieve not being standard, that sieve may be checked by counting the number of openings per linear LABORATORY METHODS 191 inch in both directions, and by measuring the diameter of the wire. Computations—For each aggregate tested, compute the percentage passing each sieve, and also compute the percentage retained on each sieve. Compute the fineness modulus of each of the aggregates. | Report—Make a tabulation showing the sieve number or Size, size of sieve opening, and, for each aggregate tested, the percentage passing each sieve, the percentage retained on each sieve, and the fineness modulus. Questions.— Which of the fine aggregates passed the specifica- tions for fine aggregates as given in the text? (See Sec. I, page 11.) Which of the coarse aggregates passed the specifications for coarse aggregates as given in the text? (See Sec. I, page 15.) Why should the materials be dry when sieved? JOB 61. SIEVE ANALYSIS CURVES Object—To plot curves showing the sieve analyses of various fine and coarse aggregates. Significance.—A sieve analysis curve for an aggregate enables an engineer to tell easily if that aggregate is well graded or not. References.—Sec. I and Job 60. Method.—On cross-section paper having, preferably, 10 divi- sions per lin. in., plot a sieve analysis curve for each of the aggre- gates tested in Job 60. Use one sheet of cross-section paper for the fine aggregates, and another sheet for the coarse aggregates. Plot percentages passing sieves to a vertical scale (ordinates), and size of sieve openings to a horizontal scale (abscissae). Consult the instructor in regard to the proper scales to use. See Appendix 3 for the sieve openings of the various sieves. Report.—With the curve sheets, include a brief description of the aggregates tested. Questions.—Judging by the curves, which aggregates appear to be well graded? Which aggregates seem to be suitable for use in concrete mixes? JOB 62. VOIDS IN FINE AND COARSE AGGREGATES Object—To determine the voids in samples of various fine and coarse aggregates. 192 CONCRETE PRACTICE Significance—Other things being equal, a denser aggregate will make a denser and better concrete. References.—Sec. I. Materials —Room-dry samples of various fine and coarse aggregates. Apparatus.—Scales capable of weighing to 200 lb. and sensitive to !4 lb., a water-tight metal measuring box or strong pail having a capacity of from 14 to 1 cu. ft., and an iron tamping rod like that described in Appendix 2. __ Method.—Weight the empty measure or pail. Fill it level full of water, and weigh it again. The weight of the water divided by 62.355 (the weight of 1 cu. ft. of water in Ibs.) will give the volume of thé measure in cubic feet. Be sure that the top of the measure is level when it is filled with water. Fill the measure with an aggregate, and tamp according to the method described in Appendix 2. Weigh the measure and aggregate. Pour water slowly in the aggregate until the measure is level full. Then weigh measure, aggregate, and water. Empty and clean the measure. Repeat the process with each of the other aggregates. Computations.—Percentage of Voids.—The total weight of the measure, aggregate, and water, minus the weight of the measure and aggregate, gives the weight of the water in the voids. The volume of the voids in the aggregate is equal to the weight of the water in the voids divided by 62.355. The ratio of the volume of the voids to the volume of the aggregate (same as the volume of the measure) multiplied by 100 gives the percent- age of voids in this aggregate. Weight per Cubic Foot.—The weight of the dry aggregate in the measure in pounds, divided by the volume of the measure in cubic feet, gives the weight per cubic foot of the aggregate. Approximate Specific Gravity——The approximate specific gravity is equal to the weight of the dry aggregate in the measure divided by the difference between the volume of the aggregate (same as the volume of the measure) and the volume of the voids. Report.—Prepare a tabulation showing all of the data taken and the results obtained. Include in the report the computation for the volume of the measure. , LABORATORY METHODS 193 The following is a sample tabulation: Material | Crushed | Gravel Sand | Ete. Weight of measure and aggregate in Weight of measure, aggregate, and Webel DOUNIS. cress... see ees Weight of water in pounds......... Volume of voids in cubic feet....... Weight of aggregate per cubic feet. .. Approximate specific gravity....... Questions.—Compare the weights per cubic foot found in this job with the weights per cubic foot found in Job 59. | Why does an aggregate composed of particles of a uniform size have a larger percentage of voids than an aggregate composed of particles of several sizes? . Why should the top of the measure or pail be level when it is filled with water? JOB 63. SILT IN FINE AGGREGATE - Object.—To determine the amount of silt in a sample of fine aggregate. Significance.—lIt is advisable to know the proportion of silt in a fine aggregate, because a comparatively large amount of silt often indicates the presence of organic impurities. A small amount of silt may ball up in a mortar, and tend to keep the cement from hardening. In some instances, however, a small amount of silt well distributed throughout a concrete mix tends to make a lean concrete more dense and waterproof. References.—Appendix 4 and Sec. I. Materials —One or more samples of fine aggregate. Apparatus.—A pan or vessel, such as is described in Appendix 4, scales, and a 500-c.c. glass graduate. Method.—Follow the method given in Appendix 4. An approximate method is to fill the 500-c.c. graduate up to the 200-c.c. mark with fine aggregate. Then water should be added until the 400-c.c. mark is reached. The aggregate and water should be agitated vigorously with a stiff wire or glass rod 194 CONCRETE PRACTICE for a time of 1 min. The graduate should then be allowed to stand until the settlement is complete. Measure the relative height of the fine aggregate and silt. Compute the percentage of silt by volume. Note that the silt does not weigh as much as the fine aggregate, hence the percentage of silt by volume is greater than the percentage of silt by weight. A rough field method is to rub a small amount of the fine ageregate in the palm of the hand, and note if it causes a dark spot or stain on the hand. Such a stain indicates silt. The presence of a comparatively small amount of silt may be determined by the eye, by observing if the sample of fine aggregate appears to be dirty, and if the grains seem to be coated. Report—Make a tabulation showing the different samples tested and the percentages of silt found. JOB 64. COLORIMETRIC TEST OF A FINE AGGREGATE Object—To determine the presence of injurious organic com- pounds in a sample of fine aggregate. Significance.—As a very small amount of organic matter in the fine aggregate may greatly reduce the strength and soundness of the concrete, it is important to detect the presence of organic matter in the aggregate. Silt is apt to contain organic matter, consequently it is not advisable to use a fine aggregate contain- ing more than 3 per cent of silt as a concrete aggregate, without first testing this aggregate for the presence of injurious organic compounds, or making strength tests on a mortar made from this © fine aggregate. References.—Appendix 5 and See. I. Materials—Samples of fine aggregates. A pparatus.—Bottles and solutions as described in Appendix 5. Method.—Follow the method described in Appendix 5. A very dark orange color or a dark brown color indicates that the fine aggregate has an appreciable amount of injurious organic matter. A light yellow or white color indicates that there is very little injurious organic matter present. In general, solutions darker than the standard solution indicate the presence of injurious organic matter. In doubtful cases strength tests of a mortar or concrete (made with the aggregate in question) should be made before arriving at a final decision. LABORATORY METHODS 195 heport.—Report on all fine aggregates tested giving the color of the liquid in the bottle in each case. State which aggregates are acceptable for use in concrete mixes. JOB 65. BULKING EFFECT OF WATER IN SAND Object.—To observe the bulking effect of water in sand. Significance—Comparatively small percentages of water (from 4 to 8 per cent) added to a dry sand will cause the sand to increase in volume. A knowledge of this bulking effect is essential when designing concrete mixes in which wet sand is used. References.—Sec. I. Materials—A sample of room-dry sand, or, preferably, a sample of sand dried to a constant weight. Apparatus.—Scales, 500-c.c. glass graduate, glass or metal rod for tamping. Method.—1. Weigh out sufficient drys and to fill the 500-c.c. graduate about half full. Place the sand in the graduate in about three equal layers, tamping each layer as described in Appendix 2. Record the volume of the sand in the graduate. 2. Weigh out an equal amount of dry sand as before, add 2 per cent of water by weight, mix sand and water thoroughly, tamp in graduate as before, and record the volume. 3. Repeat the process using 4, 6; 8, and 10 per cent of water. Record the results. 4. Make one trial with enough water just to flood or inundate the sand. Record percentage of water used, and the resultant volume. If sufficient graduates are available, each mixture of sand and water can be left in its respective graduate. Placing these gradu- ates in order in a row will illustrate the bulking effect of water very nicely. Report.—Make.a tabulation showing the percentages of water added and the percentages of increase in volume (bulking) of the sand. Questions—What percentage of water appeared to give the maximum bulking effect for this particular sand? How did the volume of the inundated sand compare with the volume of the dry sand? 196 CONCRETE PRACTICE JOB 66. TENSILE STRENGTH OF CEMENT MORTARS MADE WITH DIFFERENT SANDS Object—To compare the tensile strength of mortars made with different sands. Significance.—It is often advisable to make strength tests on mortars made from sands to determine if the sands are suitable for mortars and concretes. References.—Sec. I. Materials —Portland cement and samples of fine, coarse, and well-graded sands. Note brand of cement. Apparatus.—Scales, three 3-gang briquette molds, glass graduate, watch, trowel, etc. Method.—Make. three briquettes using each kind of sand. Follow method given in Appendix 1 for mixing and molding briquettes. All mixes are 1:3 by weight. About 125 g. of cement and 375 g. of sand are required for three briquettes. Knowing the percentage of water required for normal consistency of the cement, obtain the percentage of water for the 1:3 mortar from Table 1 of Appendix 1. It may be necessary slightly to vary the values given in the table for the different sands in order to get a workable mix. Storage.—One day in moist air and then in water. Testing.—Break all briquettes at an age of 28 days. If time does not permit, the briquettes may be broken at 7 or 14 days. Weigh each set of briquettes before testing. 3 Report.—Tabulate the individual and average results for each sand together with the brand of cement, kind of sand, percentage of water, weights of briquettes, ete. Include in this tabulation the results of the 28-day tensile test made on the 1:3 mortar of standard Ottawa sand. If available, include the weights per cubic foot of the sands. Questions — Which sand made the strongest mortar? Why? Which sand made the heaviest (or densest) briquettes? Were the heaviest briquettes the strongest? JOB 67. TENSILE STRENGTH OF CEMENT MORTARS OF DIFFER- ENT PROPORTIONS Object.—To determine the effect of varying the amount of the cement on the tensile strength of the mortar. LABORATORY METHODS 197 Szignificance—Other things being equal, the greater the pro- portion of cement, the greater the strength of the mortar. References.—Sec. I. Matervals—Portland cement and a fairly well-graded sand. Note the brand of cement. Apparatus.—Scales, three 3-gang briquette molds, glass graduate, watch, trowel, etc. Method.—¥ollow the method of mixing and molding given in Appendix 1, and make nine briquettes as follows: Three briquettes, 1:1 mix, using 250 g. of cement and 250 g. of sand. Three briquettes, 1:3 mix, using 125 g. of cement and 375 g. of sand. Three briquettes, 1:5 mix, using 80 g. of cement and 400 g. of sand. Compute the percentage of water required for each mix by the formula: Percentage of water = By eg t 65 Where P = percentage of water for normal consistency of cement, and nm = number of parts of sand to one of cement. The percentage of water is based on the combined weight of the cement and the sand. For example, if the cement requires 24 per cent of water for normal consistency, the percentage of water for a 1:3 mortar is found by substituting in the formula as follows: Percentage of water for a 1:3 mortar = eet se = + 6.5 = 10.5 per cent. If there were 500 g. of cement and sand, the amount of water needed would be 500 X 10.5 per cent or 52.5 c.c. (or grams). Storage.—One day in moist air and then in water. Testing.—Break all briquettes at an age of 28 days. Report.—Tabulate the individual and average results for each mix, together with the brand of cement, kind of sand; proportion of mix, percentage of water, etc. , Question.—What conclusions may be drawn from the results of this test? 198 CONCRETE PRACTICE JOB 68. CONSISTENCY OF PORTLAND CEMENT CONCRETE Object—To determine the consistency of a mix of portland cement concrete by means of the ‘‘slump”’ test. Significance.—The best results are obtained in concrete work when the least amount of mixing water is used that will give a concrete of just workable consistency for the job in question. Concrete that is to be used in floors and thin walls requires a little more mixing water than if it were to be used in heavy foun- dations or massive concrete work. References —Appendices 7 and 8 and Jobs 9 to 13 inclusive. Materials—Portland cement and room-dry fine and coarse aggregates. The maximum size of the coarse aggregate should not be more than 1/4 in. Note the brand of the cement and the kinds of the aggregates. Apparatus.—Measuring boxes, scales, water-tight mixing plat- form, shovels, trowels, pail, watch, and slump test apparatus as described in Appendix 7. If a concrete mixer is used, the mixing platform is not needed. Method.—Follow methods given in Appendix 7 for the slump test, and in Appendix 8 for mixing a batch of concrete by hand. In laboratory work, the amount of water is frequently given as a percentage of the weight of the cement or of the total weight of the dry materials. On the job, the amount of mixing water is usually given as the number of gallons of water per sack of cement. Thus the water may be either weighed or measured. Either way is satisfactory, provided the scales and measures are accurate. If either, or both, of the aggregates are wet, the amount of water present in the aggregates must be determined and allow- ance made. The amount of water in any aggregate may be found by weighing a sample of the aggregate, drying this sample to constant weight, and weighing again. The difference between the two weights gives the amount of water that was present. If the aggregates are thoroughly room dry, the amount of water in the aggregate is probably quite small and may be neglected. Make a batch of 1:2:4 concrete by volume, using just enough water to give a mix of workable consistency. Perform the slump test. Record the proportions of the mix, amount of water used, and observed slump in inches. LABORATORY METHODS 199 Report.—Include in the report the brand of cement, kinds of aggregates, proportions of mix, amount of water used, slump, and any other data of importance. Questions—How many gallons of water per sack of cement were required? What is the water cement ratio (ratio of volume of water in cubic feet to volume of cement in cubic feet in this mix)? If the weights per cubic foot of the aggregates are available, what would be the proportions of the mix by weight? Assume that 1 cu. ft. of cement weighs 94 Ib. What should be the maximum slump permitted for: 1. Mass concrete? 2. Reinforced concrete of a. thin, vertical sections and columns? b. heavy sections? c. thin, confined horizontal sections? 3. Mortars for floor finish? JOB 69. PROPORTIONING CONCRETE BY ARBITRARY PROPORTIONS _ Object—To proportion concrete mixes. by arbitrary proportions. Stgnificance.-—Proportioning concrete mixes by volume by arbitrary proportions was (and still is in many localities) the generally accepted method of proportioning. At the present time this method is used for most small jobs, but is being super- ceded by more scientific methods for the large jobs. References——Appendices 7 and 8; Sec. I; Jobs 1, 2, and 10 to 13, inclusive. Materials —Portland cement and room-dry fine and coarse ageregates. The maximum size of the coarse aggregate should not exceed 144 in. Note the brand of the cement and the kinds of aggregates. | A pparatus.—Measuring boxes, scales, mixing platform, shovels, trowels, and six (or nine) cylinder molds 6 in. in diameter and 12 in. high, with machined metal base plates and capping plates. A hydraulic compression testing machine (or a universal test- ing machine), scales, calipers, and ruler. 200 CONCRETE PRACTICE -Method.—Quantities.—Using Fuller’s rule (Job 12) compute quantities of cement, fine and coarse aggregates to make two (or three) cylinders of concrete for each of the following mixes by volume: 1:2:4, 1:3:6, and 1:4:8. Consistency.—Use enough water in each mix to give a consist- ency having a slump of 6 in. Note amount of water required in each case. | Norsr.—If a compression testing machine and cylinder molds are not available, this job may be discontinued at this point. Mixing and Molding.—Mix and mold each set of cylinders according to the method given in Appendix 8. The cylinder molds and base plates should be thoroughly oiled with a heavy oil before the concrete is placed in them. The capping must be carefully done if consistent results are to be obtained. Storage.—Store cylinders as directed in Appendix 8. Testing.—When the cylinders are 28 days old, weigh them, measure their diameter and height, and test them as directed in Appendix 8. Note the maximum (ultimate) load applied to each cylinder, and the manner of failure. For each cylinder, compute the weight per cubic foot, cross-sectional area, in square inches, and the unit ultimate compressive strength. Report.—Tabulate all data and results including the propor- tions of each mix, water-cement ratios, unit weights of materials (if available), weights and dimensions of the cylinders, maximum loads applied, unit strengths, ete. Questions.—If the unit weights of the aggregates are available, what are the proportions of the different mixes by weight? How many gallons of water per sack of cement were used in each mix? Did there appear to be any relation between the unit ultimate compressive strength, and the weight per cubic foot of cylinders of the same mix? ; How do the unit compressive strengths obtained for the different mixes compare with the values given by Curve A of Fig. 3, page 18? JOB 70. PROPORTIONING CONCRETE BY THE USE OF THE TABLES OF THE 1924 JOINT COMMITTEE REPORT Object —To proportion a concrete mix, having a slump of 6 in., to give a compressive strength of 2000 lb. per sq. in. at the LABORATORY METHODS 201 age of 28 days by the use of the tables given in the 1924 Report of the Joint Committee on Standard Specifications for Concrete and Reinforced Concrete. (See Appendix 6.) Significance.-—These tables have been prepared to give suitable proportions of portland cement, fine and coarse aggregates to obtain a concrete of desired compressive strength at an age of 28 days, when control tests (28-day compression tests on cylinders) are not to be made. References—Appendices 2, 3, 6, 7, and 8; Sec. I; and Jobs 1, 6, and 10 to 13, inclusive. Materials—Portland cement and room-dry fine and coarse aggregates. The maximum size of the coarse aggregate should preferably be 114 in. Note the brand of the cement and the kinds of the aggregates. Apparatus.—Scales, measuring boxes, and tamping rods, as in Appendix 2 and Job 59; scales and sieves, as in Appendix 3 and Job 60; slump test apparatus, as in Appendix 7; mixing platform, scales, shovels, trowels, and two or three 6- X 12-in. cylinder molds, as described in Appendix 8. If sufficient cylinder molds are available, it is better to make the cylinders in sets of three, instead of sets of two, as given in this and the following jobs. Method.—Determine the weight per cubic foot of each aggre- gate (if not previously determined) as in Job 59. Make sieve analyses of the aggregates as in Job 60. ‘From the tables in Appendix 6, determine the required mix, having a slump of 6 in., to give a compressive strength of 2000 Ib. per sq. in. at an age of 28 days, paying particular attention to the rules given in Appendix 6 for determining the limiting sizes of the aggregates. Compute the quantities of materials required to make two 6- X 12-in. cylinders. Mix the concrete for these two cylinders, using enough water to give a slump of 6 in. when tested as directed in Appendix 7. Make the cylinders according to the directions given in Appen- dix 8. Store the cylinders as directed in Appendix 8. Weigh, measure, and test cylinders at an age of 28 days accord- ing to the methods given in Appendix 8. Observe the maximum 202 CONCRETE PRACTICE (ultimate) load applied, and the manner of failure for each cylinder. If the unit weights and sieve analyses of these aggregates have been determined in preceding jobs, the values found may be used for this job. Report.—Compute the unit ultimate compressive strengths of the cylinders tested. Compute the water-cement ratio, and the number of gallons of water used per sack of cement. Questions ——Did the proportions selected give a greater or less unit ultimate compressive strength than 2000 Ib. per sq. in.? How does the average unit ultimate compressive strength obtained in this job compare with the unit strength given by Curve A of Fig. 3, page 18? JOB 71. PROPORTIONING CONCRETE BY THE WATER-CEMENT RATIO AND SLUMP TEST Object—To proportion a mix of concrete by the water-cement ratio and the slump test to obtain a mix having a slump of 6 in. and a unit ultimate compressive strength of 2000 lb. per sq. in. at an age of 28 days. Significance—The water-cement ratio is the important ele- ment governing the compressive strength of a concrete mix. The strength may be said to vary inversely as the number of gallons of mixing water per sack of cement, irrespective of the amount of aggregate present, provided the concrete mix has a workable consistency. This consistency of the mix may be controlled by the slump test. References—Appendices 2, 7, and 8, Sec. I; Jobs 1, 7, and 10. to 13, inclusive. Materials—Portland cement and room-dry fine and coarse aggregates. The maximum size of the coarse aggregate should not be more than 144 in. Note the brand of cement and the kinds of aggregates. Apparatus—Slump test apparatus described in Appendix 7 and scales, measuring boxes, mixing platform, shovels, trowels, two 6- X 12-in. cylinder molds, etc. for making concrete cylin- ders. If unit weights are to be found, the apparatus described in Appendix 2 will be needed. LABORATORY METHODS 203 Method.—Determine the weights per cubic foot of the fine and coarse aggregates by the method in Appendix 2, if these weights are not available from previous jobs. Thoroughly mix the fine and coarse aggregates according to one of the following proportions. (a) If the coarse aggregate appears to be uniformly graded and has a suitable proportion of the smaller sizes of particles, use a 1:2 mix by volume (1 part of fine aggregate to 2 parts of coarse aggregate); or (b) If the coarse aggregate does not appear to be uniformly graded, or if a suitable proportion of the smaller sizes of particles are not present, use a 2:3 mix by volume (2 parts of fine aggregate to 3 parts of coarse aggregate). Obtain the weight per cubic foot of the mixed aggregate by the method given in Appendix 2. From Curve A of Fig. 3, page 18, 7/4 gal. of water per sack of cement should give a concrete having a unit ultimate compres- sive strength of 2000 lb. per sq. in. at an age of 28 days. Note the water-cement ratio. Ona water-tight mixing platform, mix thoroughly a half sack of cement (47 lb.), 334 gal. of water, and enough of the mixed ageregate, so that the resulting concrete will have a slump of 6 in. when tested by the slump test. If care is taken in the adding of the mixed aggregate and water to the cement it is possible to obtain a mixture having a slump of 6 in. without much trouble. Norre.—In laboratory work, it is often preferable to weigh the materials. Cement weighs 94 lb. per cu. ft., water weighs 62.355 lb. per cu. ft. or 8.35 lb. per gal., while the unit weights of the fine, coarse, and mixed aggregates may be found by the methods given in Appendix 2. Mold two (or three, if molds are available) 6- X 12-in. cylin- ders by the method given in Appendix 8. Store the cylinders as directed in Appendix 8. Weigh, measure, and test the cylinders at an age of 28 days. Note the maximum (ultimate) load applied, and manner of failure of each cylinder. Compute the ultimate unit compressive strength of each cylinder. Report.—Include in the report all essential data, computations, and results. 204 CONCRETE PRACTICE Questions.—What were the proportions by volume of the cement to the mixed aggregate? What were the proportions by weight? What were the proportions by volume of cement, fine aggre- gate, and coarse aggregate? What were the corresponding pro- portions by weight? Was the average unit ultimate compressive strength more or less than 2000 Ib. per sq. in.? | How did the water-cement ratio in this job compare with the ratio of the preceding job? How did the proportions of the mix in this job compare with the proportions in the preceding job? How did the unit ultimate compressive strength of the concrete in this job compare with the strength obtained in the preceding job? Were the same aggregates used in both jobs? How did the unit ultimate compressive strength obtained in this job compare with the value given by Curve A of Fig. 3? JOB 72. PROPORTIONING CONCRETE BY THE WATER-CEMENT RATIO, SLUMP, AND FINENESS MODULUS OF AGGREGATE Object—To proportion a mix of concrete by the water-cement ratio, slump test, and fineness modulus of the aggregate, to obtain a mix having a slump of 6 to 7 in., and a unit ultimate compressive strength of 2000 lb. per sq. in. at an age of 28 days. Significance—The compressive strength of the mix is con- trolled by the water-cement ratio, the workability by the slump, and the economy by the grading of the mixed aggregate, as evidenced by the fineness modulus. References—Appendices 2, 3, 7, and 8; Sec. I; Jobs 1 and 8 to 13, inclusive. Materials.—Portland cement and fine and coarse aggregates. The maximum size of the coarse aggregate should not be more than 1144 in. Note the brand of cement and the kinds of aggregates. Apparatus.—Apparatus for sieve analyses as described in Appendix 3, apparatus for determining unit weights as described in Appendix 2, slump test apparatus as described in Appendix 7, LABORATORY METHODS 205 and scales, measuring boxes, mixing platform, shovels, trowels, two 6- X 12-in. cylinder molds, etc., for making concrete cylinders. Method.—If there is any doubt in regard to the quality of the fine aggregate, it should be tested for silt and organic impurities as described in Appendices 4 and 5. The relation between the compressive strength and water- cement ratio shown by Curve A of Fig. 3, page 18, will be assumed to apply on this job, because working conditions in the laboratory should be such that the proportioning can be accu- rately controlled. The detailed method of procedure given in Jobs 8 and 9 should be followed. The tests for slump and harshness should not be omitted. Using the proportions determined, compute quantities of materials required for two 6- X 12-in. cylinders. Mix the concrete and make the cylinders as directed in Appendix 8. Store the cylinders as directed in Appendix 8. Weigh, measure, and test the cylinders at an age of 28 days, according to the methods given in Appendix 8. Observe the max- imum (ultimate) load applied and the manner of failure for each cylinder. Compute the ultimate unit strength of each cylinder. Report.—Write a complete report for this job including all data and results. Questions.—Did the proportions selected give a greater or less ultimate compressive strength than 2000 lb. per sq. in.? Prepare a simple tabulation showing a comparison of the results obtained in Jobs, 70, 71, and 72 in regard to proportions, water-cement ratio, slump, and strength. Were the same aggre- gates used in all three jobs? JOB 73. EFFECT OF VARYING THE AMOUNT OF MIXING WATER IN A GIVEN MIX Object—To determine the effect of varying the amount of the mixing water on the consistency and compressive strength of a concrete mix. Significance-—It is advisable to use the smallest amount of mixing water that will give a workable mix, because the strength of a concrete mix varies inversely as the water-cement ratio. 206 CONCRETE PRACTICE Increasing the quantity of mixing water in a mix of given pro- portions will increase the workability or slump, and will also decrease the compressive strength. References.—Appendices 7 and 8; Sec. I; Jobs 1 and 10 to 13, inclusive. Materials—Portland cement and room-dry fine and coarse aggregates. The maximum size of the coarse aggregate should not be more than 114 in. Note the brand of the cement and the © kinds of aggregates. Apparatus.—Scales, measuring boxes, mixing platform, shovels, trowels, eight 6- X 12-in. cylinder molds, and the slump test apparatus described in Appendix 7. Method.—Compute quantities of cement, fine and coarse aggregates, to make two cylinders using a 1:2:4 mix by volume. 1. Make two cylinders using enough water to give a slump of about 1 in. 2. Make two cylinders using 10 per cent more water than in (1). Observe the slump. 3. Make two cylinders using 25 per cent more water than in (1). Observe the slump. 4. Make two cylinders using 50 per cent more waten than in (1). Observe the slump. Observe how readily the water flushes to the surface when tamping the cylinders in the molds. Record the amount of water used in each batch. Follow the methods given in Appendices 7 and 8 when mixing, testing for slump, and molding the cylinders. Store the cylinders as directed in Appendix 8. Weigh, measure, and test all cylinders at an age of 28 days, observing the maximum (ultimate) load and manner of failure for each cylinder. Report.—Compute the water-cement ratio for each of the four mixes, and the unit ultimate compressive strength of each cylinder. Prepare a simple tabulation showing all essential data and results. Questions—Which consistency produced a concrete of the greatest strength? Was there any general relation between the weights of the individual cylinders and their compressive strengths? LABORATORY METHODS 207 Was there any general relation between the water-cement ratios of the different batches and their compressive strengths? How did the unit compressive strengths obtained compare with the values given by Curve A of Fig. 3, page 18? How did the slumps obtained compare with the general statement made in regard to quantity of mixing water and slump in Job. 10, page 47? JOB 74. EFFECT OF VARYING THE FINENESS MODULUS OF THE AGGREGATE ON THE ECONOMY OF THE MIX Object—To determine the effect of varying the fineness modu- lus of the mixed aggregate on the economy of the mix. Significance—The amount of mixed aggregate, which may be added to a given quantity of cement and water to produce a mix with a certain slump, increases as the fineness modulus increases (and vice versa), as long as the mix is not too harsh. In other words, for a mix of a given strength and workability, the coarser the mixed aggregate, the greater the quantity or proportion of this mixed aggregate which may be used, and the greater the economy of the mix. References -—Appendices 2, 3, 7, 8; Sec. I; Jobs 1 and 8 to 13, inclusive. Materials—Portland cement and dry fine and coarse aggre- gates. The maximum size of the coarse aggregate should not be more than 114 in. Note brand of cement and kinds of aggregate. Apparatus—Apparatus for unit weights of aggregates, sieve analysis, and slump test, as described in Appendices 2, 3, and 7, respectively, and scales, measuring boxes, mixing platform, shov- els, trowels, six 6- X 12-in. cylinder molds, etc., for making concrete cylinders. Method.—Determine unit weights of the dry fine and coarse aggregates according to method given in Appendix 2. Make sieve analyses of the fine and coarse aggregates (accord- ing to the method given in Appendix 3), and compute their fineness moduli. Combine the fine and coarse aggregates in different proportions to give three mixed aggregates having fineness moduli of about 5.2, 5.9, and 6.6, respectively. 208 CONCRETE PRACTICE Using a water-cement ratio of 1 (7.50 gal. per sack of cement) and a slump of from 6 to 7 in., make three batches as follows: 1. Using the mixed aggregate with a fineness modulus of about 5.2. Note the proportion of mixed aggregate used, and then mold two cylinders. 2. Using the mixed aggregate with a fineness modulus of about 5.9. Note the proportion of mixed aggregate used, and then mold two cylinders. 3. Using the mixed aggregate with a fineness modulus of about 6.6. Note the proportion of mixed aggregate used, and then mold two cylinders. Follow the methods given in Appendices 7 and 8 when testing for slump and molding the cylinders. Store the cylinders as directed in Appendix 8. Weigh, measure, and test all cylinders at an age of 28 days, observing the maximum (ultimate) load and manner of failure for each cylinder. Compute the unit ultimate compressive strength of each cylinder. If the work has been carefully done, the individual strengths of the cylinders should be about the same. Report.—Prepare a simple tabulation showing all essential data and results. Questions.—Which value of the fineness modulus of mixed ageregate gave the most economical mix? What general conclusion may be drawn from the results of this job, in regard to the relation between the fineness modulus and the quantity of the mixed aggregate which may be added to a definite amount of cement and water to produce a certain slump? How did the unit compressive strengths found in this job compare with the value given by Curve A of Fig. 3, page 18? Did the unit compressive strength of any cylinder (or cylinders) vary greatly from the average of all? If so, was there any apparent reason for this variation? JOB 75. EFFECT OF VARYING THE FINENESS MODULUS OF THE AGGREGATE UPON THE SLUMP, AND UPON THE WATER- CEMENT RATIO REQUIRED FOR A GIVEN SLUMP Object—To determine the effect of varying the fineness modu- lus of the mixed aggregate: (a) upon the slump with the pro- portions of cement, water, and mixed aggregate remaining LABORATORY METHODS 209 constant; and (b) upon the water-cement ratio required with the slump and proportions of cement and mixed ageregate remaining constant. Significance—With the proportions of cement, water, and mixed aggregate remaining the same, an increase in the fineness modulus (coarseness) of the mixed aggregate will increase the slump of the mix. With the slump and proportions of cement and mixed aggregate remaining the same, an increase in the fineness modulus (coarseness) of the mixed aggregate will decrease the amount of mixing water required to produce the given slump, and thus decrease the water-cement ratio and increase the strength of the mix, as long as the mix is not harsh. fveferences.—Appendices 2, 3, 7, 8; Sec. I; Jobs 1 and 8 to 13, inclusive. Materials.—Portland cement and dry fine and coarse aggre- gates. The maximum size of the coarse aggregate should not be more than 114 in. Note brand of cement and kind of aggregates. Apparatus.—Apparatus for unit weights, sieve analysis, and slump test as described in Appendices 2, 3 and 7, respectively, and scales, measuring boxes, mixing platform, shovels, trowels, six 6- X 12-in. cylinder molds, etc., for mixing concrete and making cylinders. Method.—Determine unit weights of the fine and coarse ageregates according to the method given in Appendix 2. Make sieve analyses (according to the method given in Appen- dix 3) of the fine and coarse aggregates, and compute their fineness moduli. Combine the fine and coarse aggregates in different proportions to give three mixed aggregates having fineness moduli of about 5.2, 5.9 and 6.6, respectively. 1. With a water-cement ratio of 1 (7.50 gal. of water per sack of cement), mix a batch of concrete, using enough of the mixed ageregate having a fineness modulus of about 5.2 to give a slump of about 3in. Note the proportion of this mixed aggregate used and the resulting slump of the mix. 2. With the same water-cement ratio and the same proportions of mixed aggregate as in (1) mix a batch of concrete using the mixed aggregate, having a fineness modulus of about 5.9. Note the slump of the mix. 210 CONCRETE PRACTICE 3. With the same water-cement ratio and the same proportion of mixed aggregate as in (1), mix a batch of concrete using the mixed aggregate having a fineness modulus of about 6.6. Note the slump of the mix. 4. With a water-cement ratio of 1 (7.50 gal. of water per sack of cement), mix a batch of concrete, using enough of the mixed ageregate having a fineness modulus of about 5.2 to give a slump of about 7 in. Note proportions of this mixed aggregate used. Make two cylinders from this batch of concrete. 5. With the same proportions of cement and mixed aggregate as in (4) mix a batch of concrete, using the mixed aggregate having a fineness modulus of about 5.9 and just enough mixing water to give a slump of about 7 in. Note amount of mixing water used, and compute the water-cement ratio. Make two cylinders from this batch of concrete. 6. With the same proportions of cement and mixed aggregate as in (4) mix a batch of concrete, using the mixed aggregate having a fineness modulus of about 6.6 and just enough mixing water to give a slump of about 7 in. Note amount of mixing water used and compute the water-cement ratio. Make two cylinders from this batch of concrete. Follow the methods given in Appendices 7 and 8 when testing for slump and molding the cylinders. Store the cylinders as directed in Appendix 8. Weigh, measure, and test all cylinders at an age of 28 days, observing the maximum (ultimate) load and manner of failure of each cylinder. Compute the unit ultimate compressive strength of each cylinder. Report.—Prepare a simple tabulation showing all essential data and results obtained in regard to the effect of varying the fineness modulus upon the slump. Prepare a similar tabulation, showing all essential data and results obtained in regard to the effect of varying the fineness modulus upon the amount of mixing water required for a given slump. Questions—From the results obtained, what general conclu- sions may be drawn in regard to the effect of varying the fineness modulus upon the slump when the water-cement ratio and pro- portion of mixed aggregate remain constant? LABORATORY METHODS 211 From the results obtained, what general conclusions may be drawn in regard to the effect of varying the fineness modulus upon the amount of mixing water required for producing a given slump, when the proportions of cement and mixed aggre- gate remain constant? Upon the water-cement ratio of a mix when the slump and proportions of cement and mixed aggregate remain constant? Upon the strength of a mix when the slump and proportions of cement and mixed aggregates remain constant? JOB 76. EFFECT OF AGE ON THE COMPRESSIVE STRENGTH OF CONCRETE Object—To observe the effect of age on the compressive strength of concrete. Signi ficance.—In general, the compressive strength of concrete increases with age, the rate of increase in strength becoming less as the concrete becomes older. References.—Appendices 7 and 8; Sec. I; Jobs 1 and 10 to 13, inclusive. Materials—Portland cement and room-dry fine and coarse aggregates. The maximum size of the coarse aggregate should not be more than 114 in. Note the brand of the cement and the kinds of the aggregates. Apparatus.—Scales, measuring boxes, mixing platform, shovels, trowels, six 6- X 12-in. cylinder molds, and slump test apparatus as described in Appendix 7. Method.—Compute the quantities of materials required for the six cylinders using a 1:2:4 mix by volume. Mix the concrete using enough water to give a slump of about 6 in., as shown by the slump test. Compute the water cement ratio. Follow methods given in Appendix 8 for making and molding the cylinders. Store the cylinders as directed in Appendix 8. Weigh, measure, and test two cylinders at an age of 7 days, another two at an age of 28 days, and the remaining two at an age of 60 or 90 days, as time permits. Note the maximum (ultimate) load applied to each cylinder, and compute its unit ultimate compression strength. Report.—Tabulate all essential data and results. 212 CONCRETE PRACTICE Questions.—What general conclusions may be drawn regard- ing the effect of age on the compressive strength of concrete? Compare the unit compressive strength at 28 days with the value given by Curve A of Fig. 3, page 18. Using the average unit compressive strength at 7 days, find the probable unit compressive strength at 28 days from the curve of Fig. 5, page 21. How does the probable unit compressive strength at 28 days, found from the curve, compare with the unit compressive strength found in the 28-day tests? JOB 77. TESTS REQUIRED FOR CONCRETE MATERIALS This article is intended to be a general summary of the tests required of concrete materials. References are given to the jobs in which more complete information may be obtained. Before the concrete materials to be used on any job are tested, representative samples must be secured of each of the materials. Appendix 1, Sec. I, and Jobs 52 and 58 contain information in regard to the sampling of materials. For information regarding tests on portland cement, refer to Sec. I, Jobs 52 to 57, inclusive, and Appendix 1. The tests usually required of portland cement are: normal consistency of neat cement paste; soundness; time of set; tensile strength of standard sand mortar; and fineness. Tests rarely called for are: specific gravity; and chemical tests. On small and medium-sized jobs, most of the fine aggregate is used without any preliminary testing, though tests are being required more frequently on sands used for concrete on large jobs. Appendices 2 to 5 inclusive, Sec. I, and Jobs 58 te 65, inclusive, give considerable information in regard to the testing of fine aggregates. Tests that may be required are: weight per cubic foot; sieve analysis; silt; colorimetric test; bulking effect of water; percentage of moisture present; percentage of voids; and tension and compression tests of mortars made with a port- land cement of known quality, and the fine aggregate in question. Coarse aggregates are rarely tested when used on compara- tively small and unimportant concrete work. On many large jobs, the coarse aggregates are now tested to determine their suitability for concrete work. Further information relating to LABORATORY METHODS 213 the testing of coarse aggregates is given in Appendices 2 and 3, Sec. I, and in Jobs 58 to 65, inclusive. Tests that are frequently asked for are: weight per cubic foot; sieve analysis; silt; percent- age of voids; and compression tests on concretes made with portland cement and fine aggregate of known quality, and the coarse aggregate in question. Water is rarely tested before using it for concrete purposes. If the water is suitable for drinking purposes, it is usually suitable for concrete mixes. Water that is not suitable for drinking pur- poses should be regarded with suspicion. Section I gives further information. Compression and tension tests are the ones usually required on’ portland cement mortars. Section I and Jobs 66 and 67 give information regarding the strength of mortars. Appendices 7, 8, and 9, Sec. I, and Jobs 1 to 14, inclusive, and 68 to 76, inclusive, give much information in regard to the pro- portioning, mixing, molding, curing, and testing of concrete. Slump tests for consistency and compression tests are often required, while cross-bending and yield tests are rarely called for. Compression and absorption tests are usually required of concrete block and brick. Cross-bending tests are sometimes asked for. References for the requirements of concrete block and brick are Appendices 11 and 12, and Job 31. Questions.—Name the tests commonly required for each of the following: portland cement, sand, crushed stone or gravel, port- land cement mortars, portland cement concretes, and concrete brick and block. JOB 78. TESTING MACHINES USED IN TESTING CONCRETE AND CONCRETE MATERIALS Testing machines (other than the Vicat apparatus, Gillmore needles, briquette molds, etc., described in Appendix 1), used for testing portland cement and cement mortars, are briquette testing machines for tensile tests, and hydraulic compression or universal testing machines for compression tests. In the automatic briquette testing machine, the load is applied at a uniform rate (usually 600 lb. per min.) by shot flowing from a hanging bucket or receptacle in the machine. ‘There are many devices for regulating the flow of shot and applying the load. 214 CONCRETE PRACTICE The machine is so constructed that the flow of shot is automati- cally stopped when the briquette breaks. The operation of the Fia. 77.—Automatic cement briquette testing machines. ordinary shot machine is as follows: See that beam balances with no load, place briquette in grips, tighten grips, start flow of shot, LABORATORY METHODS 215 keep beam balanced by turning hand crank, observe and record breaking load when briquette breaks. The capacities of the automatic briquette testing machines are usually 1000 lb., though 2000-lb. machines may be purchased. A hydraulic compression machine of from 50,000- to 200,000-Ib. capacity is useful for crushing mortar and concrete specimens where the ultimate strength is desired. Most of these machines Fig. 78.— Hydraulic compression testing machine. consist of a strong frame with an oil cylinder, in which oil is pumped by a hand or power pump. In operating the machine, the specimen is placed squarely in the center of the lower bearing block, the upper bearing block is brought down to the top of the specimen and tightened by means of the hand wheel at the top of the machine, the load is applied by pumping oil into the cylinder, and the load (represented by oil pressure) is read by means of the oil-pressure gages. One of the bearing blocks (preferably the upper) should be a spherical block. When the specimen is 216 CONCRETE PRACTICE accurately centered in the machine, the spherical joint of this block helps to correct any slight lack of parallelism in the upper and lower surfaces of the specimen. The most common type of testing machine is the universal testing machine. The essential parts of this machine are a weighing platform for supporting the specimen, levers, a scale Fic. 79.—Universal testing machine. beam for measuring the load, and a pulling head connected to a gear system for applying the load. The weighing platform, levers, and scale beam are somewhat like those of an ordinary weighing scale. ‘The load is applied by means of a pulling head and screws (usually two, three, or four in number) operated by a set of gears attached to a motor or line belt. This pulling head can be operated at several different speeds. The load is always applied by a downward movement of the pulling head. Usual LABORATORY METHODS 217 capacities of universal machines used in laboratories vary from 50,000 to 200,000 Ib. In making compression tests (as of mortar or concrete speci- mens), a bearing plate is attached to the under side of the pulling head, and another bearing plate placed in the center of the weighing table. One of these bearing plates should have a spherical joint to care for a possible slight lack of parallelism in the upper and lower surfaces of the specimen. The specimen is placed on the lower bear- ing block, so that the vertical axis of the specimen and block are in the same line. The pulling head is then lowered until it is just in contact with the top of the specimen. The load is applied by moving the pulling head slowly downward, and the amount of the load is measured by moving the poise on the scale beam and keeping this beam balanced. A spherical bearing block is a necessary Lo adjunct for making compression tests. F1e.80.—Spherical bear- The spherical joint permits the part of the antes bearing block in contact with the specimen to move and eet itself to the test conditions. Questions.—Briefly describe the operation of an automatic cement briquette testing machine shown in the figure accompany- ing this job. Why should a spherical bearing block be used in a compression test? Briefly describe the operation of a universal testing machine when making a compression test. SECTION VI FIELD WORK INSPECTION OF CONCRETE WORK It is the duty of the inspector on concrete work to see that the contractor provides the materials called for, and does the work in accordance with the specifications and plans. Any deviations from the specifications and plans should be reported to his superior (engineer, architect, or owner, as the case may be). The inspector should be reasonable in his relations with the contractor, and should, as far as he is able, endeavor to see that the contrac- tor and owner both get a “‘square deal.’”’ The inspector should not be too rigid and arbitrary in requiring the contractor to con- form exactly to the plans and specifications, neither should the inspector permit any material deviation, however slight, from the requirements that would materially injure the work. A good inspector, who understands his work, soon wins the confidence and respect of a good contractor. A good inspector can often do much to aid the progress of the work, and at the same time to secure a good, satisfactory, workmanlike job. If the contractor and his workmen know how, and try, to do good work, the inspector’s job is an easy one. If the contractor and his men know how, but appear unwilling, to do good work, care, firmness, and continued vigilance are required of the inspector. When the contractor and his men do not appear to know how to do good work, the inspector must be firm and tact- ful, and endeavor to teach the workmen the correct methods for securing good results. If the inspector does not know his work, or if he is tactless, overbearing, and overcritical, he may cause considerable trouble and expense, both for the owner and a good contractor. A dishonest contractor will often take advantage of a lax and ignorant inspector. The duties of an inspector on concrete work may be summarized as follows: 218 FIELD WORK 219 1. Excavation.—The inspector should observe if the earth has been excavated to the depths and dimensions called for. In case of backfill, he should see that the earth is properly placed and tamped. 2. Materials—No materials should be used until they have been inspected and approved as to kind, quality, sizes, ete. When required, representative samples should be collected for testing. 3. Forms.—The inspector must require that the forms be made and erected according to the requirements of the specifications and plans. He should check the dimensions inside of the column and beam forms. He should see that the forms are clean and properly wetted or oiled before the concrete is poured. He should require that all debris be removed from the inside of the forms, and that all opénings for removing debris be properly closed before pouring concrete. | 4. Reinforcing Steel— When the steel is placed in the forms, the inspector should check sizes, bends, and spacing of rods. He should see that chairs and other steel supports and spacers are properly and securely placed, and that all ties are correctly made. In columns, the vertical rods must be securely tied to the spirals. 5. Mixing Concrete——The mixing machinery must be clean and in good working order. No concrete should be mixed unless the inspector is on the job. He must see that the materials are charged to the mixer in the correct proportions (especially cement); that the correct amount of mixing water is used to give the consistency (and strength) called for; and that the concrete is thoroughly mixed before being discharged from the mixer. The mixing and transporting machinery must be washed and cleaned at the end of the run or of the day’s work. 6. Placing Concrete-—The concrete should be taken from the mixer and placed in the forms before initial set has occurred. On the way from the mixer to the forms, the inspector should observe if the mix appears to have the right consistency and uniformity, and if there is any segregation of the materials. The inspector should note if the mix is carefully placed in the forms, and spaded and tamped to give a good dense concrete, free from air pockets, and with a smooth surface next to the forms. The 220 CONCRETE PRACTICE inspector must be careful to see that new concrete is carefully bonded to old concrete, according to the directions given. 7. Curing of Concrete-—The inspector should observe if the curing conditions are such as to give satisfactory results, and that the specifications are carefully followed in this respect. 8. Removal of Forms—The inspector must see that the forms are removed at the correct time and in the proper order. The workmen should be careful not to chip, spall, or otherwise injure the concrete surfaces. 9. Surface Finish—The inspector must note if all fins and projections are removed, and that all porous places are cut out and holes filled with suitable mortar or concrete. When a cer- tain surface finish is required, the nspe must see that this work is properly done. 10. Cleaning Up.—After the work is completed and the struc- ture and premises cleaned up, the inspector should make a final inspection to see if the cleaning is properly done, and that the place is left in good shape. 11. Reports.—The inspector should make all reports (usually daily ones) required of him in regard to his work. ‘The reports may deal with materials delivered and used, forms made and erected, steel bent and placed, concrete mixed and poured, forms removed, surface finished, etc., as may be required by his superior. In addition to the routine part of the report, the inspector should note and report the general progress of the work, and any unusual or important matters dealing with the job. A diary, carefully and conscientiously kept day by day in regard to the work, is a great help. SUPERVISION OF CONCRETE WORK The supervisor or foreman in charge of concrete work should try to obtain average quality and maximum quantity of work in the minimum amount of time. Foremanship, in general, consists of the ability to organize the gang, and to efficiently direct and supervise the work by properly dividing the work among the workers, educating the workers when necessary, coordinating the work of the different individuals, developing an esprit de corps or gang spirit, exercising tact and forbearance, and doing all that he can to secure satisfactory work at minimum cost. FIELD WORK 221 Quality of concrete work depends upon good materials, proper tools and plant, correct methods of work, and good workmen. Good workmen in concrete are those who have sufficient educa- - tion, skill, aptitude, and experience to turn out satisfactory work in an efficient manner. ! Quantity of concrete work may be secured by use of good tools and methods, by correct location and arrangement of the plant, by proper organization of the gang, by the selection of good, efficient workers, by the development of gang speed, and by the avoidance of delays and idleness of the plant or of the workmen. To be efficient, the concrete plant for a small concrete job must be of the right size for the job. The mixer should be located as close to the forms as practicable. The pile of coarse ageregate should be closer to the mixer than the pile of fine ageregate. The cement for a day’s run (or at least for a half day’s run) should be piled close to the mixer so that the mixer tender or operator can also handle the cement. The plant should be so laid out that the total amount of labor per cubic yard of concrete will be a minimum. The concrete gang must be organized so that each man will be busy all the time. The time lost, due to delays and idleness, must be reduced to a minimum. Plant delays may be reduced considerably if the mixer operator keeps the mixer in good working order. Minor repairs, adjustments, greasing, etc. should be made outside of regular working hours. Idleness may be reduced by providing just enough workers for each class of work. For example, if two men can shovel and measure aggregates for the mixer, it is useless to have three men for this part of the work. Motion and time studies are advantageous in determining the most efficient ways of doing certain kinds of work. The studies tend to show what motions are needed for a certain type of work and what motions are wasteful and unnecessary. After the proper method of doing the work has been found, the worker must be taught and trained to follow these methods until he does the work easily and efficiently. There is also a certain ‘‘knack,” or way of doing work, that some men acquire more quickly than others. For example, an experienced shoveler in mixing con- crete does not try to fill his shovel by a short stroke or a jab at the 222 | CONCRETE PRACTICE pile, but slides his shovel on the mixing platform and fills it gradually and uniformly over a stroke of about 2 ft. A foreman or superintendent should try by every possible means to avoid accidents to the workmen or plant. Accidents either to workers or plant cause delays and increased costs. Workers must be cautioned in regard to the use of certain parts of the plant, such as scaffolds, runways, ladders, etc. Plant accidents may be reduced by careful inspection at fairly close intervals. Guards should be provided for gears, chains, shafts, flywheels, etc., whenever practical. The following are some of the principles for securing minimum costs of concrete work: 1. The sum of all of the units of cost should be a minimum. 2. The plant and men should be worked to capacity. 3. Delays and idleness should be reduced. 4. Plant and work should be arranged.and organized to make the labor a minimum. 5. Low-priced men should be used for low-priced work, and skilled labor used only when required. 6. Overhead and plant expenses should be reduced to a minimum. 7. A gang spirit (idea of best company, best gang, best boss, best men in that class of work) should be developed. 8. The most profitable part of the work should be done first. When investigating costs of concrete work it is well to express each cost item as a percentage of the whole. Any items which are exceeding the percentage values assigned to them should be studied as to the cause and possible remedy. When trying to reduce costs, it is usually better to study the larger items first. The most efficient work may not always mean the fastest work but it does mean the work which was done for the least cost. The jobs in the Field Work Section are each divided into two parts—descriptive matter and field jobs or problems. In most instances, the descriptive matter is not intended to be complete but is intended to be supplementary to the material previously given in the text. While no back references are given, it is assumed that the preceding material has been studied and will be restudied when necessary. FIELD WORK 223 - The field jobs or problems are frequently divided into two parts, (a) and (b). When so divided, the object of jobs (a) is to observe, record, and study the work done by others; and the object of jobs (b) is actually to do the work. Study, observation, and practical work are all necessary for a thorough understanding on concrete practice. JOB 79. CONCRETE BASEMENT—STAKING OUT The best and easiest way to stake out a basement is by the use of surveying instruments. When such instruments are not 5S S H WN Sel NS Botter boords > £2 ae } Plumb bob =f [> DGialade line of ut > . i i foundation wall AY; NIG is WOR _ 4 yl , yu | = ’ - * 2 Fig. 81.— Method of staking out a foundation. available, a 50- or 100-ft. steel tape may be used for measuring, and a carpenter’s level and straightedge for leveling. First a base line, marking one end or side of the basement, is established at the place where the proposed building is to be erected. Beginning at suitable points on this base line, lines for the other sides of the basement are laid out. In Fig. 81, line AB is the base line, and stakes A and B are driven at the corners of the basement. ‘Then the other lines AD, BC, and CD are located, and stakes sometimes placed at corners C and D. Nails may be driven in the tops of the stakes 224 ; CONCRETE PRACTICE to locate the exact corners, or the inside edges of the stakes may be used to determine corners, and the batter boards omitted. Right angles may be laid out at any corner by the following method: Drive stake F (see Fig. 81) on line AB, and 6 ft. from stake A. Place nail in top of stake F exactly 6 ft. from nail in top of stake A. Drive stake # 8 ft. from stake A, and 10 ft. from stake F. Place nail in top of stake H exactly 8 ft. from nail in stake A, and exactly 10 ft. from stake F. Angle HAF is a right angle. Measure line AD (line AE prolonged), and locate point D. In like manner, lay off BC at right angles to AB, and locate point C. Measure BC for check. For a final check, measure the diagonals AC and BD. ‘These two diagonals should be exactly of the same length if the points A, B, C, and D form a perfect square or rectangle. If the lengths of the two diagonals are not exactly equal, move points C and D a little, and check distances again. Repeat process until the corners A, B, C, and D are located correctly. Erect batter boards 2 or 3 ft. from each corner, as shown in Fig. 81. The horizontal boards are often set level with the top of the proposed foundation wall, or a certain definite distance above or below. Suppose that the horizontal boards are placed at corner A first, and made level by use of the carpenter’s level. — Then the batter boards at corners B and D may be placed, and the elevations of the horizontal boards found by sighting along boards G and H, or by sighting along a leveled straightedge fastened to one of these boards. The elevations of the horizontal batter boards at C must be checked by sights from both B and D, and errors corrected. | Strings may be stretched vertically over the corner stakes A, B, C, and D by use of a plumb bob. Notches or nails are placed in the batter boards where the strings are fastened to mark the correct places in case the strings should be broken or removed. After having located the basement corners and lines, it is comparatively easy to locate any piers, posts, columns, or other supports for the building, either inside or outside of the building line as the case may be. Problems.—Stake out a building foundation for a basement 24 X 32 ft. in size, setting corner stakes, batter boards and strings, assuming that the top of the foundation wall at point A is to be 2 ft. above the surface of FIELD WORK 225 the ground. Be sure that diagonals AC and BD check. Correct length of each diagonal in this job is 40 ft. Materials needed will be six stakes, twelve posts, eight boards, about fifty nails, a ball of heavy twine, a plumb bob, a good carpenter’s level, a 50 or 100 ft. metallic tape, a straightedge, a hammer, and an axe. Notre.—Other dimensions for the basement may be selected, if desired. JOB 80. CONCRETE BASEMENT—ESTIMATING The estimate for a concrete basement will be divided into five parts: . Staking out. . Excavation. . Forming. . Concreting. . Removal of forms. The method of staking out a basement was explained in the preceding job, and a list of materials given for staking out a simple rectangular basement. If old lumber is used, the cost of materials will be small. The labor required for staking out a simple basement will usually vary from 1 to 4 hr. for two or three men, depending on conditions. The volume of earth to be removed in excavations will be equal _to the area of the basement times the average depth of the bottom of the basement below the ground surface. When the ground surface is a plane surface (either level or inclined), it is compara- tively easy to find this average depth. If the ground surface is rolling or uneven, the basement area may be divided into several small areas (from 25 to 100 sq. ft., for example), and the average depth for each area approximately determined. Then the - volumes due to each area times its depth are computed and summed up to obtain the total. For a small basement where the dirt is to be used for grading around the place, the dirt may be removed by two men with a team and a scraper, and a shoveler or two. When the dirt is to be hauled away, it is usually shoveled directly into wagons or trucks. On comparatively large jobs, steam shovels and drag- line scrapers may be used. Plows or picks may be used for loosening the dirt. The form lumber for basement walls may be either 1-in. ship- lap or 1-in. boards, about 6 to 10 in. wide, and planed on one side. or Wd 226 CONCRETE PRACTICE If the outer dirt walls of the basement are firm and smooth, they will serve as outer forms. For braces and struts and shores, 2 < 4’s are commonly used. On many jobs, the form lumber for the basement is carefully salvaged and used for rough lumber in ii Fig. 82.—Method of computing excavation. the building. Planks are usually provided for constructing run- ways for the concreting gang. For ordinary walls, the vertical struts or cleats may be spaced about 2 ft. on centers. A net- work of cross-bracing from one wall to the opposite wall is often used instead of the bracing of wall forms shown in Figs, 26, 27, Fig. 83.—Small concrete batch mixer. 28, 84, and 85. When the braces extend from the vertical struts to the ground, the lower side of these braces must be securely butted against stakes driven in the ground, and the upper ends fastened to the vertical struts. Cross-bracing from wall to opposite wall is to be preferred. FIELD WORK 227 For an average basement wall, the proportions of the concrete mix usually vary from 1:2!4:5 to 1:4:7 when separate fine and coarse aggregates are used, and from 1:6 to 1:9 in the case of mixed aggregates (like bank run gravel). The thickness of the basement wall for a small basement may vary from 6 to 12 in., 8 in. and 10 in. being common. In regard to concrete plant, a half-bag or a one-bag concrete mixer is commonly used. The crew required will vary from two or three men with a half-bag batch mixer to from four to six men with a one-bag batch mixer. In building work, the basement wall forms are removed in about 10 days to 3 weeks after placing the concrete, and the form lumber carefully salvaged, nails removed, boards cleaned, and piled for later use. The labor cost of form removal may be quite large, but is worth while as the salvaged lumber is used again. Problems.—Make a complete estimate of materials and labor for a basement with concrete walls. Size of basement is 24 X 32 ft., and walls are to be 8 in. thick and 7 ft. 6 in. high. Average depth to be excavated is 5 ft. 3 in. Concrete mix is to be 1 part of portland cement, measured by the sack, to 7 parts of bank run gravel, measured loose by volume as thrown into a measuring box or calibrated barrow or hopper. Notrr.—lIf an actual basement is to be staked out and excavated, use dimensions for that basement. 1. Estimate materials and labor required for staking out. 2. Estimate quantity of excavation (in cubic yards) and labor (man, team, scraper, and two helpers). 3. Estimate form lumber in board feet, and labor in hours for forms. Assume outer dirt walls of basement to be firm and satisfactory as outer forms. 4, Prepare a bill of material for the form lumber. 5. Estimate quantities of cement and bank run gravel required. 6. Estimate labor and plant (mixer, barrows, shovels, etc.) for con- creting, assuming a half-bag or a one-bag batch mixer for mixing, and barrows for placing the concrete. 7, Estimate labor required for removing forms, removing nails, and clean- ing and piling form lumber. JOB 81. CONCRETE BASEMENT—EXCAVATION The excavation of small basements is frequently let for a lump sum or for a certain price per cubic yard. The lump sum contract is usually more satisfactory than day labor. 228 CONCRETE PRACTICE When the dirt is to be used for grading on the lot, no dump wagons or trucks are needed. ‘The top soil is removed first by the scraper, and piled in one corner of the lot. This top soil is used for surfacing later on. A plow may be needed to loosen the soil from time to time. The scraper can remove about 80 or 90 per cent of all the dirt, and the remainder must be shoveled. Shovelers are required to square the corners, smooth the walls af the dirt is comparatively stiff and firm), and to remove the last few cubic yards. When the dirt is to be hauled away, dump wagons and teams are commonly used. A wagon is placed in the basement area and loaded by a shovel gang. The number of men in the shovel gang may vary from two or three to six or eight, depending on the desired time of loading the wagon. An extra wagon or two should be provided, so that a wagon can be loaded while the teams are on the road. The first team arriving unhitches from its empty wagon and hitches on to the loaded wagon. As the basement gets deeper, an extra team (snatch team) is required to help ‘‘snatch”’ or pull the loaded wagon out of the basement. The number of shovelers, wagons, and teams required depends upon the length of haul and desired rate of progress. The whole gang should be organized so that neither shovelers nor teams will be idle during the working hours. More than one wagon may be loaded at a time if the size of the basement permits. Auto trucks are often not economical when they have to be loaded by shovelers. If the size of the excavation is large enough to warrant the use of a steam shovel, then auto trucks may be used. When boulders are found, the smaller ones may be carried or hauled out of the excavation. Larger boulders may be broken by sledges, drills and wedges, or explosives. Blasting is frequently necessary, when solid rock is encountered when excavating. ; Problems.—a. Observe the work of excavating a basement for a resi- dence, noting dimensions, quantities excavated, number of men, teams, wagons, scrapers, etc., on the job, and the work done by the different classes of labor, and the time spent on each class of work (plowing, scraping, shovel- ing, hauling, etc.). Compute the total hours of labor for both men and teams, and compare the results with reasonable estimates. FIELD WORK 229 b. Excavate a basement, noting kind of earth, quantities excavated, number of men, teams, plows, scrapers, wagons, etc., used, and the cor- responding time. Compare actual labor hours required with the estimated hours. JOB 82. CONCRETE BASEMENT—FORMING Under similar conditions, the amount of forming lumber required for’a given basement will not vary greatly, but the LEZ -Z77] \ \ \ \ - RN S . ° ° ° ° ° ® aa S a) ZZAZL LEN Br eee Se." : Ses 7/7 LED PAA 3 a a [N a FFE eT Fig. 84.—Foundation wall forms. amount of labor hours expended may vary greatly. For example, experienced, capable, and fast men can build interior wall forms for a 20- X 30-ft. basement, with a depth of about 7 ft. in about 24 labor hr., while other workers may spend as much as 80 230 CONCRETE PRACTICE labor hrs. on a similar job. Building the forms for each wall on the floor of the basement, and then erecting them, often saves considerable time. No more nails should be used than necessary. Pieces of lumber about 1 in. square, with a length equal to the thickness of the wall, make suitable spacers to keep the forms the required distance apart. These spacers may be removed as the concrete is placed. Wire ties are satisfactory for keeping the forms from spreading. WD SSUDSSEPSN TIS. NUN Fig. 85.—Foundation wall forms below grade. (The embankment serves as the outer form.) If the form carpenters are to set the runway planks for the concrete gang, care must be taken to secure the planks so that they will not move easily when the barrows and men pass over them. Care should be taken in regard to projecting the ends of planks beyond supports. Such a plank may tip up and cause a serious injury to a workman. Partially green lumber is usually satisfactory for form work, as dry lumber may swell, and too green or wet lumber may shrink. FIELD WORK 231 Problems.—a. Inspect a job when basement wall forms are being con- structed, noting the amounts, kinds, and sizes of the form lumber used, together with the nails, spacers, and ties. Make a bill of material for the forms. Record the hours of labor required to construct the forms. b. If not previously done, make a bill of lumber and materials required for the wallforms for the basement previously excavated. Construct the wall forms for the basement, noting the materials used and labor hours expended. JOB 838. CONCRETE BASEMENT—CONCRETING Before starting the concreting work for the basement, the materials and plant needed should be on the job. The quanti- ties are not large, comparatively, and there should be no difficul- ties in regard to the storage space needed. The forms should be inspected to see if they are rigid and tight and well constructed. All rubbish should be removed from the interior of the forms. The surface of the forms with which the concrete will come in contact should be thoroughly wetted before concrete is poured. ‘The surfaces could be oiled, but most build- ers prefer a good wetting with water. The concrete plant should be examined to see if the mixer is clean and in good working order. Enough oil and gasoline should be on hand so that no delays will be caused by lack of them. The barrows, carts, shovels, and other tools to be used should be clean, and in good working order. The runways should be examined to see if they are well constructed and correctly placed for the work. The crew for a one-bag mixer will be approximately as follows: One man who acts as foreman, runs mixer, and adds cement and water to the mix. Two or three men to measure and load the aggregates in the hopper of the mixer. Two or three men to wheel and place concrete, depending on the capacity of the barrows or carts, and the size of the batch. One man to spade (and sometimes tamp) concrete in forms so as to get smooth surfaces, to remove spreaders, place stop boards, etc., and help barrow men when necessary. In general, the size of the crew should be such that the plant will be used efficiently and all men will be busy. A _ half-bag mixer will require a crew of about four men for efficient work. 232 CONCRETE PRACTICE Whenever possible, the pouring of the concrete basement walls should be finished in 1 day. If necessary to stop work for a day before the concreting is completed, the joints between the old and new concrete should preferably be made horizontal. On beginning work again, all laitance and dirt should be removed from the surface of the old concrete before the new concrete is deposited thereon. If several days should elapse before the concreting is resumed, laitance and dirt should be removed from the surface of the old concrete and this surface roughened. A rich, thin cement grout should be applied to the old surfaces before the new concrete is deposited. ‘The new concrete should be placed before the grout has attained initial set. When the forms are full, the tops of the walls should be leveled and smoothed off. At the end of the job, at the close of a day’s work, or at any time when the process of mixing and placing concrete is inter- rupted for 14 hr. or more, the mixer and barrows (and other tools with adhering concrete) should be cleaned and washed. Problems.—a. Inspect a job when concrete basement walls are being poured, noting the size or capacity of mixer, size of batch, time required for mixing and placing a batch, the number of men in the crew and the duties of each, the amount of concrete mixed and placed, the time required, and the general methods of conducting the work. b. Mix and place the concrete required to fill the forms constructed in Problem (b) of Job 82. Note organization and duties of workers, average size of batch, amount of concrete placed, required time of placing, and any other useful information pertaining to the work. JOB 84. CONCRETE BASEMENT—REMOVAL OF FORMS Basement wall forms should not be removed until the concrete has attained hard set, and has become strong enough to sustain its own weight and the loads that may soon be placed on it. The time required before the forms should be removed. will vary from a few days in very hot weather to several weeks in very cold weather. Before removing the forms, the concrete should be examined to see if it is hard and firm. The forms should be carefully removed, so that the lumber will not be broken or split, the concrete cracked, or the surfaces marred. Nails should be removed from the form lumber, the boards cleaned, and the lumber neatly piled for future use. FIELD WORK 233 Fins and projections on the exposed concrete surface should be removed. Holes should be filled with a mortar of about the same proportions as that in the concrete. Spongy and porous places should be cut out, and the cavities filled with a concrete or mortar of the same proportions as that in the walls. Problems.—a. Inspect a job when the forms are being removed from some basement walls, noting the appearance of the concrete, the care and manner in which the forms are removed, and the form lumber cleaned and handled, the amount of forms removed (square feet of form surface), and the labor hours required, the patching (if needed) of the concrete surfaces, and any other items of importance. b. Remove forms from the basement walls of Problem (6b) of Job 88. Remove nails, clean and pile lumber, and patch concrete surfaces. Note amount of form surface removed, labor hours required, and labor and materials required for patching surfaces. JOB 85. CONCRETE SIDEWALKS—SPECIFICATIONS AND ESTIMATES The following are general specifications in a condensed form for one-course and two-course concrete sidewalks. These speci- fications are practically the same as those proposed by the Portland Cement Association. Cement.—Portland cement meeting the standard specifications for port- land cement (Appendix 1). Fine Aggregate.—Clean and well-graded natural sand or screenings, from a hard and tough crushed rock, gravel, or slag. All shall pass a No. 4 sieve, and 95 per cent or more shall be retained on a No. 100 sieve. Coarse Aggregate.—Clean, hard, durable, uncoated pebbles, crushed stone, or blast furnace slag. All shall pass a 1-in. sieve and 95 per cent or more shall be retained on a No. 4 sieve. Water.—Shall be clean enough to drink. Joint Filler—Premolded strips of bituminous filled fiber or mineral aggregate, 14 in. thick, as wide as the thickness of the walk, and 2 ft. or more in length. Forms.—Shall be of lumber 2 in. thick, or of steel of equal strength. Flexible strips may be used on curves. All forms shall be rigidly held to line and grade by stakes or braces. Division Plates.—Shall be of 1<-in. steel, as wide as the depth of the walk, and as long as the width of the walk. Subgrade.—Shall be well drained and compacted to a firm surface with uniform bearing power. Drains.—When necessary, 4-in. concrete or clay tile drains should be laid to protect the walk from possible damage by frost action. 234 CONCRETE PRACTICE Subbase.—On poorly drained soil or where tile drains are impractical, a 5-in. subbase of cinders, gravel, or other porous material shall be used. This material shall be thoroughly tamped and drained to a street gutter or other outlet. Thickness and Proportions of One-course Walk.—The concrete shall be at least 4 in. thick in residence districts and 5 in. thick in business dis- tricts. The proportions of the mix by volume shall be 1: 214: 4 for residence districts, and 1:2:3 for business districts. Thickness and Proportions of Two-course Walk.—In residence districts, the base course shall be at least 414 in. thick of a1:3:5 mix by volume. In business districts the base course shall be O4 4 in. thick, of a 1:3:5 mix by volume. The top course shall be at least 34 in. thick, oot the proportions of the mix shall be 1 part cement to 2 parts ane aggregate by volume. Mixing.—Concrete shall be mixed until each particle of fine aggregate is coated with cement, and each particle of coarse aggregate is coated with mortar. A batch mixer is preferred. Consistency.—The least amount of water should be used that will give a workable mix. The fresh concrete should require tamping to bring the water to the surface. Placing and Finishing One-course Walk.—Concrete shall be placed immediately after mixing. It shall be tamped, struck off with a template, and then floated with a wood float until the surface has a true contour. Care shall be taken not to bring an excess of water and fine aggregate to the surface by overfinishing. Placing and Finishing Two-course Walk.—The base course shall be thoroughly compacted by tamping, and then struck off with a template, which shall leave the upper surface of the base course 34 in. below the finished surface. The top coat shall be placed within 45 min. after the base course is laid. The top course shall be struck off and finished with a wood float until the surface has a true contour. Curing.—The new concrete shall be protected Hs a canvas or burlap covering for a day, after which the concrete shall be kept wet for 7 days. Problems.—Prepare an estimate of the materials, labor, and plant required for 200 ft. of one-course, concrete sidewalk, 5 ft. wide, assuming the following: Residence district. Average depth of excavation is 8 in. Subbase shall be 5 in. of cinders, with no tile drains. Nortr.—Instructor may vary conditions of this problem to conform with requirements of the next two (b) problems. JOB 86. CONCRETE SIDEWALKS—LOCATION, GRADE, BASE, AND FORMS In residential sections, walks are usually placed along the property line and a strip of lawn or parking is left between the walk and the pavement. Walks in the interior of the lot may be FIELD WORK 235 placed where desired, and, when carefully located, will add to, rather than detract from, the appearance of the property. It is usually better to curve walks around a fine tree, instead of remov- ing the tree. The minimum width of walk in residence districts should be about 5 ft. In business and industrial districts, the walks usually extend from the building line to the curb, in order to give the needed width. Stronger walks are needed in these districts. In general, it should be planned to have the surface of the finished walk level with, or a trifle above (about 1 in.), the sur- face of the ground. Also the grade line of the walk should be approximately parallel to that of the pavement. A little study in regard to the grade line and location of the walk is well worth while when after effects are considered, especially when cuts or fills are encountered. The slope of the walk for drainage should be about 14 in. to the foot. The direction of the slope wil! often be determined by the slope of the surrounding ground. ‘The slope may be to one side, to the other side, or to both sides, as desired. In preparing the subgrade, the ground should be excavated to the depth desired, and all grass, sod, sticks, roots, and other vegetable matter removed. The surface of the subgrade should be tamped and compacted until it has a uniform bearing power. All soft and spongy places should be dug out and replaced with good earth, solidly tamped. Places in the subgrade that are harder than the average should be loosened and then tamped, so as to have the same bearing power (or degree of compactness) as the remainder of the subgrade. Fills must be solidly compacted in about 6-in. layers. Muck, quicksand, sod, soft clay, spongy or perishable material should not be used. Fills should extend about 1 ft. beyond the edges of the walk to prevent undermining of the concrete during rains. When practical, it is well to allow the fill to settle for some time before the walk is constructed. Good drainage of the subgrade is essential. If the subgrade is naturally well drained, no drain tile or cinders are needed. If the subgrade is water soaked, the best remedy is drain tile placed about 1 ft. or so under the walk, and near the edge from which most of the water comes. In many instances, a subbase of a 236 CONCRETE PRACTICE porous material (say a 5-in. layer of cinders) is advantageous. A. drain must be provided to carry away the water from this porous material, or it cannot serve its purpose. Sidewalk forms may be of wood or of metal. Straight forms should be of wood 2 in. thick, or of metal of equal strength. Flexible strips may be used for curves. Forms must be set true to line and grade, and securely held in place by stakes and braces. The top of the forms should correspond with the finished grade of the walk. After the side forms are placed, division lines should be marked on them at intervals to locate the position of the cross forms and to mark the dividing lines to be cut through by the groover. The intervals should not exceed 6 ft., and 5-ft. intervals are common in most localities. Metal cross forms have been found to be very satisfactory. These forms should be placed at the marked intervals, so as to be perpendicular to the walk surface and to separate the slabs. Construction joints are the separation planes between the slabs, and are formed by the removal of the metal cross forms. The edges of these joints should be slightly rounded. Expansion joints are placed at intervals of about 50 ft. in the walk, and between the walk and the curb, or a wall or a building. Expansion joints are usually 14 in. wide, except that a 1-in. joint should be provided between walks and curbs. The joint filler should preferably be a bituminous-filled fiber 14 in. thick as wide as the walk is thick, and as long as the walk is wide. Problems.—a. Inspect the preparation of the subbase and forms for a concrete sidewalk, noting the average depth of excavation, condition of surface of subgrade, drainage (tiles, cinders, etc.), width, length, and thickness of walk, kind of walk (one or two course), kind of forms, workman- ship in regard to placing of forms, provisions for cross forms and expansion joints, and labor expended for excavation, drainage, and forms. b. Excavate and construct subbase and forms for a concrete sidewalk, as directed by the instructor. Note the amount of excavation, drainage — provisions, amount and kind of forms, and labor required for excavation, drainage provisions, and forms. JOB 87. CONCRETE SIDEWALKS—CONCRETING, FINISHING, AND CURING Before starting concrete work, the forms and subbase should be inspected to see if they are correctly constructed, and the FIELD WORK 237 Fia. 86.—Side forms are set, the subgrade Fic. 87.—Concrete is dumped onto the smoothed off and metal division plates subgrade by barrows or direct from mixer installed. bucket. Fig. 88.—The concrete is spaded against Fig. 89.—This wooden screed is worked the forms and then struck off with a screed back and forth, bringing enough mortar to or template. the top to make a smooth surface. Fig. 90.—A wood float or belt smooths Fig. 91.—After the surface is finished, the the surface and the edges are rounded with division plates are lifted out, the surface is an edging tool along the side forms and the protected with canvas and kept wet for a division plates. week. Figs. 86—91.—Construction of one-course concrete sidewalks. 238 CONCRETE PRACTICE concrete plant examined to see if it is clean and in working order. The materials for the work should be available on the job, or at least enough of the materials for a day’s work. Shortly before starting concreting, the surfaces of the metal forms should be well oiled, while the wooden forms may be oiled or wetted. If a half-bag batch mixer is used, the concreting gang will probably consist of from two to four men, mixing and placing concrete, and one finisher. With a one-bag mixer, from four to seven men may be used for mixing and placing, and one finisher and one helper for finishing. Two-coat work requires more labor for mixing and placing than one-coat work does. Care should be taken, when measuring, to see that the materials are correctly measured. Placing materials in the mixer by shovelsful is not measuring. A bottomless measuring box should be used to measure the aggregates. Cement may be measured by the sack. Wheelbarrows may be used for measuring if their capacities are known, or if the inside of the barrow is marked to show the height to which the barrow is to be filled. A batch mixer should be used whenever possible, and the mix- ing continued for at least a full minute. The drum must be completely emptied, before receiving the next batch. If hand mixing is used, precautions must be taken to secure thorough mixing (see Job 13, page 51). In one-course work, the concrete is placed a little high in the forms, tamped, and then struck off by a template riding on the side forms. A heavy template will compress the concrete a little. In two-course work the base course is placed at about the height of the side forms, tamped, and struck off by a template leaving the concrete surface 34 in. below the top of the forms. The wearing course is placed soon after the base course (never more than 45 min. later), tamped, and struck off ready for the finisher. If the base course has commenced to harden before the top course is placed, the top course may crack and scale off. Concrete for each slab should be placed continuously, so that all parts of each slab will harden together. Whenever work must be stopped, as at the noon hour, or at the close of the day, it is best to stop work only at the end of a slab. FIELD WORK ~ Fia. 92.—A base course of dry mix is tamped 34 inch below the finished grade. Fic. 94.—After the striking-off process the surface is finished with a wood float and the edges tooled to a rounded corner. Fie. 96.—At regular intervals a dry sand joint is made in the _ base-course; the mortar top is grooved above this joint. . Fic. 93.—The 34-inch mortar top follows close after the tamping and is struck. off with a screed or template. Fig. 95.—When desired, a very smooth finish may be obtained by using a steel trowel. Fig. 97.—Edging tools are used, both along the forms and at the cross joints to give proper finish to the walk. Figs. 92—97.— Construction of two-course concrete sidewalks. 240 CONCRETE PRACTICE Most concrete walk surfaces are now finished with a wood float, as a metal float makes a smooth slippery surface. After the concrete has been struck off, it should be smoothed with the float, high spots leveled off, low spots filled, and excess water worked to the edges of the side forms. ‘Too much troweling brings water to the surface, and causes a chalky surface. Float marks may be removed by brushing the surface with a calcimine brush dipped in water. If a rough surface is desired, this may be made by lifting the wood float vertically away from the surface. The edges of each slab next to the side forms and construction joints should be rounded to approximately a 14-in. radius with steel edging tools. ' Figures 86 to 97, inclusive, give a good idea of the methods of finishing one- and two-course concrete walks. Special surfaces may be obtained by using different types of aggregates for the top surface, or by finishing the surface by different methods. When colored effects are desired, only mineral coloring matter should be used, so as not to reduce the strength of the concrete. The weight of the coloring matter should not be more than 8 per cent of the weight of the cement. The cement and coloring matter should first be mixed dry. A sample should be made first, to see if the proportions selected give the desired color effect. The following mineral colorings may be used to secure various colors: CGLOR CoLorina MATERIAL Pink to red Red iron oxide Browns Brown iron oxide Yellow to buff Tron hydroxide Gray to blue slate Carbon black or manganese dioxide White White cement, white sand, and white rock © Concrete hardens best when kept moist. Consequently, immediately after the surface of the walk is finished, the walk should be covered with canvas or burlap placed a little above, and not in contact with, the surface. This covering may be removed after a day or so, and the walk kept wet by sprinkling for a period of at least 7 days. After 1 week or 10 days, the side forms may be removed and earth tamped in the holes left by the forms. FIELD WORK 241 Problems.—a. Inspect the concreting and finishing of a concrete sidewalk, noting the length, breadth, and thickness of the walk, whether one- or two- course work, proportions of mix, kind of plant, size of mixer, crew and their duties, the amount of concrete placed in cubic feet, and in square feet of walk surface, and the labor hours used. b. Concrete and finish the concrete sidewalk for which the subgrade and forms were constructed in Problem (b) of the preceding job (Job 86). Note the organization of the crew, the amount of concrete placed, and the labor required. Pay careful attention to the curing of the concrete. Remove forms after an interval of 1 week or 10 days. JOB 88. CONCRETE CURBS AND GUTTERS There are three classes of concrete curbs and gutters: (1) separate curb; (2) combined curb and gutter; and (3) integral curb and gutter. Separate concrete curbs are rarely made, because of the joint next to the curb, where the water may work pees filler Construction Jour apie seer Gane hole apy eg Ming fess Desde as Eee ee ae See Fia. 98.—Cross section of Fic. 99.—Cross section of Fie. 100.—Cross sec- integral curb and gutter. combined curband gutter. tion of separate curb. through to the subbase. Combined curbs and gutters are good, though there is a joint between the gutter and the pavement. The integral curb and gutter are constructed simultaneously with the concrete pavement, and without any joints between the pavement and curb and gutter. The face of a concrete curb should be sloping and the corners well rounded, because such a curb and gutter are more easily kept clean and also cause no damage to tires, rims, and wheels of motor cars, parked alongside the street. The construction of the integral curb and the combined curb and gutter is illustrated in Figs. 101 to 112, inclusive. Typical cross-sections are shown in Figs. 98,99, and 100. ‘The height and width of the curb and gutter vary in different localities and on different jobs. Metal form surfaces should be oiled, and wooden form surfaces may be oiled or thoroughly wetted shortly before concreting. 242 CONCRETE PRACTICE Fia. 101.—Setting curb forms on Fiag. 102.— Building up integral curb returns. on returns. Fig. 103.—A simple form for integral Fig. 104.—F acing the curb after curb. forms are removed. Fia. 105.—Finishing with specially Fia. 106.—Giving final finish with shaped trowel. brush. Fias. 101-106.—Construction of integral curb. FIELD WORK 243 Fie. 107.—Placing concrete in forms. Fig. 108.—Tamping concrete to ap- proximate contour. Fic. 109.—Striking off base course Fig. 110.—Finishing with curb and mortar facing. machine. Fig. 111.—Edging—note division Fia. 112.—Finishing with brush. plates. Fries. 107—-112.—Construction of combined curb and gutter. 244 CONCRETE PRACTICE The following specifications are practically the same as those recommended by the Portland Cement Association: Condensed Specifications for Integral Curb Cement.—Portland cement meeting the standard specifications for portland cement (Appendix 1). Fine Aggregate.—Clean and well-graded natural sand or screenings from hard, tough, crushed rock, gravel or slag. All shall pass a No. 4 sieve, and 95 per cent or more shall be retained on a No. 100 sieve. Coarse Aggregate.—Clean, hard, durable, uncoated pebbles, crushed stone, or blast furnace slag. ‘All shall pass a 114-in. sieve and 95 per cent or more shall be retained in a No. 4 sieve. W ater.—Shall be clean enough to drink. Joint Filler—Shall be premolded strips of bituminous filled fiber or mineral aggregate 14 inch thick, and of the actual section of the curb. Forms.—Shall be of lumber 2 in. thick or of steel of equal strength. Flexible strips may be used on curves. Shall be held in place with suitable clamps to prevent bulging. Subgrade.—Shall be well drained and compacted to a firm surface, with a uniform bearing power. Proportions.—Shall be 1 part cement, 2 parts of fine aggregate, and not more than 8 parts of coarse aggregate by ype or the same as are used for concrete pavement. Expansion Joints.—A 1-in. expansion joint shall be made at every. joint in the pavement, and should be in perfect alignment with the joint material. When curbs are molded to shape by use of forms, the joint in the curb shall be made with a tapered separator of oiled wood 44-in. thick at the top and cut to the exact section of the curb. The filler must effect a complete separation between adjacent sections of the curb. Mixing.—Concrete shall be mixed until each particle of fine aggregate is coated with cement and each particle of coarse aggregate is coated with mortar. A batch mixer is preferred. Consistency.—The least amount of water should be used that will give a workable mix. The fresh concrete should require tamping to bring the water to the surface. Placing.—Concrete shall be placed immediately after mixing. It shall be tamped and spaded until a coat of mortar is adjacent to the forms, so that no coarse aggregate will show when the forms are removed. Finishing.—Concrete shall be struck off flush with the top of the forms, and shall be given a true finish with a wood float anda brush. If stone pock- ets appear when forms are removed, they shall be filled with cement mortar and troweled. Corners and edges shall be rounded. Concrete shall be struck off and finished true to cross-section. Finish with a float or curb tool and brush. Round the corners and edges. Forms to remain in place at least 24 hr. Curing.—Finished concrete shall be kept wet for 7 days. FIELD WORK 245 Problems.—a. Observe the construction of a concrete curb and gutter, and note details in regard to plant, materials, mix, forms, labor (organization and amount), and placing, finishing, and curing of concrete. b. Make a complete estimate of materials, forms, plant, and labor required for 100 ft. of combined curb and gutter, using cross-sectional dimensions selected by the instructor. Set forms, organize gang, and construct the 100 ft. of combined curb and gutter. Record materials, labor, forms, and plant used. Compare actual quantities and results with those estimated. JOB 89. CONCRETE PAVEMENTS—DESIGN, SPECIFICATIONS, AND ESTIMATES A properly designed concrete pavement will be well located, well drained; will have a good firm foundation or subgrade of uniform supporting power; will be of ample width for the present and near future traffic; will have a section of the correct sectional dimensions for the kind of traffic and type of subgrade; will have well-constructed construction and expansion joints; and will be constructed of concrete of the most economical proportions and consistency. The location of a city pavement is almost invariably deter- mined in advance, and the location of a county highway nearly always. Relocation of highways and questions of grade, align- ment, curves, cut and fill, drainage, subgrade, design of sections, etc., should be left to the judgment of well-qualified engineers. Good drainage is very important, and often determines the “life” of the pavement. Well-constructed side ditches should be built to care for the surface drainage of highways and take the water away from the roadway, and thus keep the water out of the foundation. The bottom of the side ditches should preferably be at least 21% ft. below the center of the roadway, and the ditches should be of ample capacity. These ditches should be provided with outlets spaced not too far apart. Culverts should be used to carry the water from one side to the other under the roadway. Subdrainage is not needed in some instances, such as in fills and where the foundation soil is naturally porous and well drained. Drain tile are required where the subsoil is not well drained or is not porous (such as clay). The drain tile should not be less than 4 in. in diameter, and should be provided with sufficient outlets to carry the water away from the foundation. Tile lines may be placed under the center of the roadway, under one edge, or under 246 CONCRETE PRACTICE each of the edges, and at a proper depth and slope efficiently to drain the water away from the foundation. The slope of a tile drain should not be less than 6 in. in 100 ft. Most every highway has some cut and fill. Excavation usu- ally does not cause much trouble if careful attention is paid to line, grade, width, and drainage. Drainage, both surface and subsurface, in cuts is important. Fills should be carefully built up in horizontal layers of not over 1 ft. in thickness. Each layer should be well compacted before the next layer is applied. When time permits, an embankment should be allowed to settle before any paving surface is applied on top of it. Large rocks, sod, sticks, stumps, etc. must be kept out of the subgrade. The subgrade should be roughly made to approximately its final shape, and then trimmed, scarified, sprinkled (if not already wan eeterene eee ene Ok a 5 Si ey (7 20 / ae ke Gauge-6}"5td Metal Parting Strip... OF Mic mmeerse led pi banc ac ial cn ; S = TES ee ee ae ee erence Sat ane, oe ————[= 2 Ce $ EN ~y 3 s Pet SECULDG Ni AR Gd PRET Ae OE OE Pe is A AWK YAY) A SRYNS YK SIS USLASULE WIV yg ee ent ee ee e i Teeny apa dN CPS. SUegtade | “MRI Ga opsh a Deformed Bars 4-0" Long, 3*1/"Ctrs." | : . es en .. Transverse Bar, Parting Strip Pin 1*3" Long- Pressed Steel Stake Section Area 11.68 sq.ft. Fig. 113.—Cross section of standard concrete pavement— Wisconsin Highway Commission. 9 iY 3 2 e damp), and rolled until the surface is well and uniformly com- pacted and ceases to creep. Rollers, varying from 2 to 10 tons in weight, have been specified by different engineers for subgrade rolling. Soft spots should be dug out and replaced by good soil placed in 6-in. layers, and each layer well tamped and compacted. The contractor should be given extra compensation if required to excavate soft spots deeper than 2 ft. It may be advisable to place a 2-in. sand cushion on some soils such as clays. . A uniform degree of compactness and supporting power is desired of the subgrade. The roadway should be at least wide enough, so that two cars can easily pass when traveling at ordinary speeds. Widths of 16, 18, or 20 ft. are common, and greater widths are provided in instances where the volume of traffic demands it. Shoulders should be usually provided along each side of the highway pave- FIELD WORK 247 ment. The width of the shoulders will vary in different localities and places. The cross-section of a city concrete pavement may be of the same thickness throughout, or the edges may be a little thinner or thicker than the center, depending on the opinion of the engineer. The thickness should not be less than 5 in. at any place, and greater depths may be needed for certain kinds of soils and types of traffic. The cross-section of a concrete highway should be made thicker at the edges than at the center, due to the tendency of --Edge of Pavement Transverse Bar Stake ee ‘Round Smoot, Races aA a races Longitudinal Bar Stake--.->4 Py Be atti he & \|_.Metal Parting Strip I ~ Concrete Slab in Place Wid Stops at Joint ‘t-Metal Pin I'-3"long 2 Paraftined Pasteboard Tube-: : 2 - Std. Metal Parting Strip Plan View a ‘Paraftined Pasteboard Tube 2+3 es £ Round Smooth Bars4-0'Long, aes of Pavement ee a oe of ee a “arting STB subgrade-" 4 SE 4 Toh loint Material - Nar more qaGn two pieces per joint. Cross Section View Fra. 114.—Transverse joint detail for standard concrete pavement— Wisconsin Highway Commission. heavy trucks to stay near the edge of the pavement. The thick- ness selected depends on the foundation, traffic, strength of concrete mix, and amount of reinforcement. At the present time, the minimum thicknesses commonly specified are 9 in. for the edges and 5 or 514 in. for the centers, with 2 ft. or more for the taper. The Wisconsin Highway ehfvcent an uses 9 in. at the edges and 614 in. at the center, with a taper extending 4 ft. back from the edge. ‘The Illinois Highway Commission uses a 9-in. edge with a center thickness of 6 in. for rural concrete highways, and a thickened edge and a 7-in. center for highways near large cities and population centers. Greater thicknesses may be required for very heavy traffic and weak and variable subgrades. 248 CONCRETE PRACTICE There is no doubt but that steel reinforcement is beneficial in concrete pavements, but engineers differ in their opinions in regard to the economy of the use of the reinforcement. The question is not yet entirely settled whether it is advisable to use steel reinforcement and a thinner slab or to use a thicker slab and no reinforcement. Ordinary pavement reinforcement may be steel fabric or steel rods properly formed into mats with dimen- sions of steel, spacings, and weights as specified. ‘The amount of reinforcement may vary from 20 to 150 lb. per sq. yd. of pavement surface. Longitudinal parting strips are used in most concrete pavements 18 ft. or more in width, and dowel pins are provided +g Smooth Roviid Bar _, _-Circular Are , 189° —-—— x SS PS PN Sets ait woot REE EE : eo Metal Joint" ‘©! Crowned subgrade “~ “7Tai* “4 Deformed Bar il vairaberdeatia sh eek ~ fy SOS ger ei eae a i = cree tage tere righ meets “ wi sCrowned Subgrade LSA ‘3 Deformed Bar Fig. 115.—TIllinois concrete highway sections. in all transverse construction and expansion joints, so as to reduce and confine the cracking and to keep the edge of one section from rising above the edge of an adjacent section. Steel reinforcement is usually provided in concrete pavements where they pass over culverts or form approaches to bridges. Transverse expansion joints should be spaced from 30 to 50 ft. apart, and should be about 1 in. wide. A bituminous-filled joint filler should be used, and not more than two pieces should be used in any one joint. Longitudinal expansion joints should be provided between the pavement and concrete curbs (unless integral curb and gutter is used), and other structures. When the pavement is over 25 ft. in width, a longitudinal joint is usu- ally provided in the center. Longitudinal parting strips are now commonly placed in the center of concrete highways. Dowels should be placed as shown in the plans. Dowels in the FIELD WORK 249 parting strip and longitudinal parts are 14-in. square or 34-in. round rods, 4 ft. long, placed 3 or 4 ft. on centers. At transverse construction and expansion joints, the dowels are usually 34-in. round rods spaced about 4 ft. on centers. At transverse expan- sion joints, one end of each dowel is placed in a tube of paraf- fined or oiled paper to prevent this end from bonding with the concrete, and to permit expansion and contraction of the slab. Concrete pavement slabs often vary from 25 to 50 ft. in length and from 16 to 25 ft. in width. When concrete pavements form approaches to bridges, the pavement section is usually widened, thickened, and reinforced. On curves, the outer edge of the pavement is superelevated, and the width is widened (usually on the inside) to make travel safer. The amount of superelevation and widening varies in different localities. The free sight distance on a curve should be at least 150 ft., and many engineers prefer a minimum of 300 ft. when practicable. Guard rails should be provided when the side slopes are so steep as to be dangerous, or when the highway passes over bridges and large culverts. These guard rails may be of several different styles. There are some patented forms of wire mesh on the market which make excellent guards, when properly placed and constructed. ‘These wire mesh guards are designed so as to be elastic and to ‘‘give”’ to some extent when an auto hits them, thus tending to reduce the amount of damage to the vehicle and injury to the passengers. The concrete materials should be inspected and tested to see if they comply with the specification requirements in each case before they are used in the concrete mixtures. The proportions of the concrete mix vary in different localities. Wisconsin uses practically a 1:2:4 mix by volume, while other mixes are 1:2:3, 1:2:314, ete. A 1:2:4 mix is about the leanest that should be used. It is often better to give a strength require- ment and proportion the materials accordingly. The least amount of water should be used that will give a workable mix. The slump of a concrete highway mix should be about 1 in. as determined by the standard slump test. In no case, should the amount of water exceed 614 gal. per sack of cement with the aggregates dry. If aggregates are not dry, the amount of water 250 CONCRETE PRACTICE in them must be found and allowed for. This corresponds to a water-cement ratio of about 0.83 and should give a concrete having a unit 28-day compressive strength of from 2250 to 2750 Ib. per sq. in. Some engineers specify the number of gallons of water per sack of cement that the contractor may use in the mix, and then let the contractor work out the grading of the aggregates to give the greatest yield and yet have a workable mix. In no case, should the amount of fine aggregate in a batch be less than half, or more than, the amount of coarse aggregate. Any method of proportioning may be used that will give satis- factory results. Common methods are: measuring cement by the sack, and sand and coarse aggregate dry in measuring boxes; cement by the sack, sand inundated in a tank, and coarse aggre- gate dry in measuring boxes; and cement by the sack, and sand and coarse aggregate dry by weight. If aggregates are wet, the amount of water contained must be found and allowance made. The bulking effect of water in sand must be considered if the sand is wet. Water may be weighed or measured by any positive automatic device which may be set and locked. The forms, plant layout, and mixing, placing, finishing, and curing of the concrete will be discussed in more detail in follow- ing jobs. The specifications for Portland Cement Concrete Pavement for Highways given in Appendix 13 are good, and should be studied in detail in connection with the jobs on concrete pavements. When preparing estimates for a concrete highway, the following items should be considered: Cut and fill. Culverts and bridge work. Preparing subgrade. Forms for pavement. Concreting plant—including mixer, water pipes, tools, finishing apparatus, canvas and burlap pavement covers, trucks or narrow- gage railway for hauling materials from source of supply to the mixer, unloading plant at railway station, steam rollers, scrapers, etc. Cement. Fine and coarse aggregate. Water. FIELD WORK . 251 Steel reinforcement. Joint fillers. Material for aiding the curing of concrete such as calcium chloride, hay and straw, sand, ete. Shoulders for the pavement. Guard rails. Labor for all of the different construction items. While the materials and plant needed may be estimated fairly accurately, it is more difficult to secure a reliable labor estimate, because of variations in labor skill and incentive to work, gang organization and spirit, possible delays due to weather and breakdowns, etc. Likewise, it is difficult for the average person to estimate unit and total costs for similar reasons, though a contractor who knows his gang and their work can make a fairly close estimate. Problems.—a. Make an estimate of the materials required for the concrete for 1.50 miles of concrete highway, 20 ft. wide, using the Wisconsin Highway Standard Sections and a 1: 2:4 mix by volume, with expansion joints placed every 40 ft. If practicable, make a complete estimate from the plans and specifications of a portion of a concrete highway in the process of being constructed, and check the estimate with actual quantities used on the job. 6b. Prepare an estimate for a portion of a concrete highway pavement according to information given by the instructor in regard to the location, length, and section. Include estimates for preparation of subgrade, forms, concrete materials, plant, and all labor involved. This pavement section should preferably be a small section, such as may be later constructed by the class. JOB 90. CONCRETE PAVEMENTS—SUBGRADE AND FORMS The subgrade should be prepared as described in the preceding job and in Appendix 13. The length of subgrade that should be prepared ahead of the concreting crew will vary, depending on the length of the pavement that the concrete gang can lay in a day. Enough subgrade for from 14 to 2 days concreting should be prepared in advance of the concrete gang. The forms used may be either of wood or metal, but good metal forms are to be preferred. The specifications in Appendix 202 CONCRETE PRACTICE 13 give the requirements for both wooden and metal forms and their setting. Fig. 116.—Setting metal forms for concrete highways. Problems.—a. Inspect the preparation of the subgrade and the setting of the forms on a concrete highway job, observing methods of compacting, wetting, and rolling subgrade, and kinds of forms, and methods of setting and aligning them. About what distance was the subgrade prepared and the forms set in advance of the concreting crew? b. Prepare the subgrade and set the forms for the section of concrete pavement to be constructed later by the students. If the concrete is not to be placed soon, the subgrade must be inspected, checked, and wet down again, just before the concrete is placed. The estimates for this section of pavement were prepared by the students in a previous job. JOB 91. CONCRETE PAVEMENTS—CONCRETE PLANT AND ORGANIZATION OF CREW It is practically impossible to state just what should be included in a concrete plant for a concrete highway job, and to give the correct organization of the crew, because each concrete highway job is a separate problem by itself and requires a partic- FIELD WORK 253 ular solution. Factors affecting this solution are equipment available, time limit of job, probable weather conditions, location of material supplies, location of job, kind and amount of labor available, and capacity and ability of contractor and his foremen. In the following paragraphs, a description will be given of a plant layout, equipment used, and labor gang and organization. It should be noted that, while a certain plant layout and crew organization may give good results on a certain job, the same plant layout and crew organization might not work efficiently on other jobs, due to factors previously mentioned. Most highway engineers prefer a mixer on the job to a central mixing plant, though the central mixing plant has proved to be economical in some instances. The mixer should be a batch Water Supply Line EEE __ Steel Forms +t Q angi ran ib ee 5 4 PEAe Concrete Concrete covered with} cova with Final Belt Bridge Stee/ Forms | A Foreman 2 E Form Setters 2 | Strike-off Board Men | B Mixer Operator | F Water Boy | K Finisher | C Batch Operator 1 G Joint Man 2 L Finishers Helpers — | D Subgrader 2H Concrete Distributors 2 MLaborers to cover finished pavement Fig. 117.—Concrete paving plant layout with three-bag mixer. mixer with a boom and bucket delivery. The mixer engine may be steam, gasoline, or oil. Oil engines seem to be preferred at present. Electric motors may be used when there is a supply of electricity available on the job. ‘The larger and medium-sized mixers should be able to move slowly under their own power. Smaller mixers can be moved a short distance by workmen when necessary. The sizes of mixers commonly used are 2-, 3-, 4-, 5-, and 6-bag batch mixers, with the larger sizes preferred, especially on large jobs. The aggregates may be hauled to the job in advance of the work and placed on or along the side of the subgrade. This requires that the materials be handled again, usually by wheel- barrows. ‘The cement, of course, cannot be placed on the job much in advance of the mixer. A water-tight platform (raised a few inches off the ground) and some tarpaulin covers will be needed for the cement. 254 CONCRETE PRACTICE The cement and aggregates may be hauled to the mixer in trucks or in industrial railway cars, and dumped into the mixer skip as needed. ‘The aggregates should be correctly proportioned for each batch at the loading plant, and each truck or car may hold one, two, or three batches, depending on the capacities of the mixer and of the truck or car. The proper amount of cement for each batch should be placed in bags on top of the aggregate for that batch. | Motor truck haulage of materials is suitable for jobs and plants of all sizes, while industrial railways are often uneconomi- cal, if used with smaller jobs. When the aggregates are hauled directly from the sand and gravel pits and stone crushers, the aggregate supply companies will usually have all bins and loading devices necessary. When, however, the contractor hauls his aggregates from a railway sid- ing, he will need machinery and appliances for unloading the cars and loading the trucks. When practical, the aggregates can be unloaded directly from the cars to trucks or bins. It is usually better to provide storage piles than pay demurrage charges. When the size of job warrants, bins should be provided for holding the aggregates and loading the trucks. Bins with weighing or measuring devices are needed when trucks are loaded by batches. A weather-tight cement storage shed capable of holding a car- load or more of cement is often essential. With batch loading, this cement shed should be located near the aggregate bins, so that the required sacks of cement can be placed on top of the ageregates for each batch. A truck turntable at the job is ahelp when batches are hauled by trucks. It is advisable to keep trucks, materials, etc., off of the pre- pared subgrade as much as possible. Any roughening or dis- turbance of the subgrade surface must be rectified before the concrete is placed. A typical organization for a 3-bag batch mixer is as follows: One foreman One joint man One mixer operator Two concrete distributers One batch operator Two strike-off board men One subgrader One finish foreman Two form setters Two finishers or helpers One water boy Two laborers to cover finished pavement EE —— FIELD WORK 290 Enough trucks and drivers should be used to keep the mixer well supplied with materials. The number of trucks needed will depend on the size of mixer or batch, the size of trucks, and the length of haul. One truck turntable man will be needed if a turntable is used. If the cement and aggregates are piled on the job in advance, three or four cement handlers, five or six fine aggregate wheelers, and eight coarse aggregate wheelers are necessary. One or two trucks will be needed for hauling cement. If the pavement is to be reinforced, one or two men will be needed to place reinforcement. When the materials are unloaded at a railway siding, and batch haulage is used, one crane operator, one or two bin operators, one cement loader, two cement unloaders (from cars to shed), and possibly two shovelers will be needed. One foreman will be needed at the siding. When advisable, some laborers may be shifted from one kind of work to another. Compared with a 3-bag batch mixer, a 6-bag batch mixer will require about 50 per cent more laborers and about twice as many trucks. Problems.—a. Inspect a highway concreting plant in operation and write a report describing the plant layout and crew organization in detail. b. In regard to the section of concrete pavement to be built by the class, overhaul plant available and place it in good ‘working order, and determine the size of crew needed, crew organization, and duties of each laborer. c. Prepare a detailed estimate of the organization required for a 6-bag batch concrete mixer, giving the number of laborers of each class and their duties. Assume batch haulage with trucks having a capacity of approxi- mately 2 cu. yd. and an average length of haul of 3 miles from railway siding to job. How many trucks are needed? Plan the materials. plant at the railway siding, and list the number of workers required and their duties. JOB 92. CONCRETE PAVEMENTS—PROPORTIONING, MIXING, PLACING, AND FINISHING CONCRETE Just before starting the concreting, the subgrade should be rechecked to see if it conforms to the specifications, and any irregu- larities corrected. The subgrade should be moist, so-that it will not absorb water from the concrete. It is advisable to sprinkle the subgrade until it does not readily absorb any more water. When desired, the subgrade may be wet down from 12 to 36 hr., before placing the concrete. 256 CONCRETE PRACTICE The reinforcement of the type, size, and weight shown on the plans prepared by the engineer should be placed as directed in the specifications (Appendix 13). Care must be taken to secure the reinforcement in its proper place, so that it will not readily be displaced when the concrete is poured. Any method of measuring the materials, including water, that will accurately give the required proportions is satisfactory. Aggregates should be dry, unless their water content is found Fic. 118.—Charging the mixer. and allowed for, or except when the sand is measured by the inundation method. The amount of water per sack of cement must be accurately controlled. The mixer should conform to the specifications in _ regard to type and operation. Some engineers require a net mixing time of 114 min. instead of 1 min., as usually specified. The mixed concrete should be deposited rapidly and uniformly over the subgrade. ‘Tamping, spading, and slicing is advisable to remove air from the concrete, and to compact it thoroughly and uniformly. FIELD WORK 257 A mechanical tamper is sometimes used as in the Vibrolithic process. In this process, a set of duck boards of definite size, with spaces between them, is placed on the fresh concrete, and a gas or oil engine, with an unbalanced flywheel, is pulled back and forth across the boards. The unbalanced flywheel, when rota- ting, acts as a tamper and thoroughly compacts the concrete. More coarse aggregate should be added from time to time, so that there will not be an excess of mortar on the pavement surface. Fig. 119.—Spreading concrete on subgrade. The concrete pavement surface may be finished according to any one of the methods given in the specifications. Some engi- neers prefer to roll the fresh concrete across the pavement with a 6-ft. wooden or metal roller after the concrete has been struck off, and before it has been belted. The roller should not weigh more than 50 Ib., should have a smooth surface, and should be from 8 to 12 in. in diameter. The roller should be built in two sections, so that these sections may be separated a little when a, joint is reached, and the concrete on both sides of the joint rolled in one operation. All portions of the concrete surface should have at least three separate rollings. 258 CONCRETE PRACTICE In regard to the finishing of joints and edges, some engineers prefer a 3g-in. or a /4-in. radius instead of the 14-in. radius, speci- fied in the standard specifications. Fria. 120.—Construction of a concrete highway. Fig. 121.—Mechanical finishes. The finished surface should be such that it will conform to the required form of cross-section without a deviation of more than 14 in. at any place. In regard to the longitudinal trueness of FIELD WORK 259 the surface, a 10-ft. straightedge placed parallel to the center line of the pavement should not show a deviation of more than 44 in. The pavement surface should be tested for trueness before the last finishing operation is begun, and concrete removed or added as needed to give the required smoothness .of surface. When concrete is added or removed at any point, the surface of this point must be completely refinished. Problems.—a. Inspect the mixing, placing, and finishing of a section of a concrete pavement or highway, noting kinds and proportions of materials, plant details, pavement cross-section, reinforcement, joints, etc., and the methods of mixing, placing, and finishing the concrete. Note the amount of pavement placed in a day’s run (square yards of surface and cubic yards of concrete), and compute the labor hours required per square yard of surface and per cubic yard of concrete. b. Wet down the subgrade and mix, place, and finish the section. of concrete pavement for which the subgrade and forms were prepared in the previous job. Compute labor hours required per square yard of pavement surface and per cubic yard of concrete. JOB 93. CONCRETE PAVEMENTS—CURING As the curing or hardening of concrete is not a ‘drying out’’ process, the concrete should be protected so that the moisture needed will not be evaporated. Concrete hardens best in the presence of moisture, hence the newly laid pavement should be covered or screened against the action of a hot sun or of a drying wind. The standard specifications for concrete highway pavements given in Appendix 13 describe the protection of the fresh concrete by burlap or canvas covers, wet earth covers, and sprinkling or ponding. To be efficient, the covering must be kept wet. Shrinkage cracks or “hair checks”’ are apt to form on the pave- ment surface during very hot and dry weather, due to the unequal shrinkage of the concrete and the exposed surface drying out a little. Working the pavement surface by tamping and belting until the hardening is fairly well advanced will help close shrinkage cracks, or help prevent such cracks from forming. Another method of preventing these shrinkage cracks is to cover the fresh concrete with burlap strips, and then keep the burlap moist, by spraying water through atomizing jets so as to keep a fine mist over it. 260 CONCRETE PRACTICE When the concrete has hardened sufficiently, so that shrinkage cracks will not form, but is not yet hard enough to permit pond- Fig. 122.—Curing concrete pavement with burlap cover. Paid i Si 4 Py ~ Fig, 123.—Curing concrete pavement with earth cover. Placing the earth cover. ing or covering with earth, the pavement surface may be pro- tected by canvas covers attached to frames. These frames span ee FIELD WORK 261 the pavement and keep the canvas a short distance above the concrete surface. Every other frame should have a strip of Fig. 124.—Curing concrete pavement with earth cover. Wetting earth cover. Fig. 125.—Curing concrete pavement by ponding. canvas to serve as a transverse partition across the pavement and thus prevent drafts along the surface. The canvas cover should be kept moist by spraying lightly with water. 262 CONCRETE PRACTICE ...When the concrete has hardened so that it may be covered with arth or ponded, the canvas-covered frames may be removed and the concrete surface protected for about 2 weeks by ponding or by an earth covering. Figures 122 to 126, inclusive, show various methods of protecting the newly laid concrete pavement. When it is practically impossible to protect the pavement surface by coverings or ponding, as in the case of some city streets, the fresh concrete surface may be kept wet by sprinkler heads arranged at suitable intervals, and connected by a hose to the city’s or contractor’s water supply. The sprinkler heads Fic, 126.—Curing concrete pavement with hay or straw cover, should be adjusted so that the water will fall on the concrete in the form of a fine spray or mist. Calcium chloride salt or crystals spread on the concrete surface (not less than 14 Ib. per sq. yd.) accelerates the hardening of the concrete, and tends to keep the surface from drying out too rapidly. The calcium chloride should not be applied until at least 24 hr. after the pavement is laid, and then only after the pavement has been kept thoroughly wet by sprinkling with water for the entire period, except the last hour just previous to the application of the calcium chloride. If rain falls within 2 hr. after the calcium chloride has been applied, an additional appli- FIELD WORK 263 cation must be made. The calcium chloride should not be applied by shovels or brooms, but may be applied by a squeegee, or a suitable mechanical device giving a uniform distribution. Coatings of sodium silicate and other materials have been used in some instances, but laboratory tests have not shown these coatings to be superior to ponding or moist earth covers. In general, no such protective measures are necessary when the temperature is 50°F. or less. While concrete hardens less rapidly at low temperatures, there is but little evaporation of moisture from the concrete surfaces. Concrete pavements preferably should not be placed during freezing weather (35°F. or less). Article 70 of the specifications in Appendix 13 gives instructions for cold weather work. Before the highway is opened to traffic, shoulders should be constructed on both sides of the pavement. The material for shoulders should be of the kind specified, and should be placed, tamped, or rolled to conform with the requirements of the plans and specifications. Problems.—a. Inspect the curing of a concrete pavement, noting methods used in detail for protecting the concrete surfaces, time required, and approxi- mate labor needed. b. Using the method selected by the instructor, protect the surface of the pavement placed in previous jobs for a curing period of 2 weeks. JOB 94. CONCRETE SEPTIC TANKS Briefly, the principle on which a small sewage disposal system operates is that of bacterial decomposition (or rotting) due to the action of bacteria. There are two classes of these bacteria: aerobic bacteria which require the presence of oxygen (air); and anaerobic bacteria, which do not need oxygen (or air). Usually the small sewage disposal system is composed of a septic tank, which is comparatively tight, and in which anaerobic bacteria work, and a distributing system, which may be a dry well, or a system of drain tile, and in which aerobic bacteria can work. A concrete septic tank should be about 5 ft. deep, as experience has shown that a depth of about 4 ft. of liquid is essential, and of sufficient width and length to care for the average amount of sewage received in 1 day (about 50 gal. per person). Baffle plates should be placed close to the entrance and discharge pipes, or else 264 CONCRETE PRACTICE the tank should have a central partition so as to lower the velocity of the liquid through the tank. Concrete baffle boards about 2 in. thick are permanent. The length of the tank should be “ _-3 Bars 4"0¢.--, House grass RSH LDS ek | Chipped vent- ane —] —-_ 4 a . ea ae WI >) a " me Bars, |2"0.c. |an eae both ways if Fia. 127.—Cross sections of single chamber septic tank and siphon chamber. approximately twice the breadth. The sewage may be dis- charged directly into the distributing system, or into a siphon chamber. The top of the septic tank should preferably be com- Fig. 128.—Forms for single chamber septic tank. posed of tightly laid concrete plank, which may be removed when the tank requires cleaning. Many authorities prefer the use of a siphon chamber, especially when tile drains are used to distrib- ute the sewage. The siphon causes a periodic discharge, which FIELD WORK 265 nts SRN Te (pT IE REEY Nah 8 Ne beets @ Peace, of erase hr rae peri oe 5 Fie. 129.—Septic tank with siphon chamber. % Rods - #’ oc. Fig. 130.—California type of septic tank, 266 CONCRETE PRACTICE tends to fill the drain tile for a time and to reduce the chance of clogging the tile near the septic tank. The use of a siphon is not so essential when a dry well is built. When drain tile are used to distribute the sewage, the tile may be arranged in two, four, or six lines and of sufficient length for the purpose. A longer system is required in a tight soil than in a porous one. The slope of the drain tile should be from 2 to 6 in. per 100 ft. of length. The table which follows gives approxi- mate lengths of tile needed for tanks of various sizes and for differ- ent soils. Drain tile 4 in. in diameter is commonly used. The tile system should have an air vent, which is usually constructed near the septic tank and spihon chamber. A dry well makes a satisfactory distributing system when the well can be carried down to sand or gravel, or to rock crevices. The bottom of the dry well should be 5 ft. or more below the bottom of the septic tank, and the horizontal cross-sectional area of the dry well should be about four or five times that of the septic tank. The dry well may be walled up with stone or brick laid loose, and a concrete cover provided. ‘This cover preferably should not be lower than the top of the septic tank. ‘The cover should be provided with a suitable manhole and cover for cleaning purposes, and an air vent should extend from the top of the dry well to the ground surface. In most instances, the dirt walls of the excavation may be used for outer forms of the septic tank and inner forms of wood con- structed as in Fig. 128. The walls and bottom of the septic tank should be 5 or 6 in. thick, and should be reinforced with woven wire or with 14-inch round rods spaced about 12 in. on centers in both directions. The reinforcement should extend down the walls and across the bottom of the tank, forming a kind of steel basket. The concrete mix should be about 1:2:3 by volaIag: good materials being used. The cover of the septic tank should be made in the form of planks, as shown in Fig. 129. These concrete planks should be 4 in. or more thick, and reinforced in the bottom with 14-inch round bars running lengthwise of the plank. The thickness of the plank and the amount of reinforcement will depend partly on the depth of dirt over the top of the tank. FIELD WORK ) 267 Figure 131, and the following table, give the dimensions of septic tanks of different capacities. These dimensions are the ones recommended by the Portland Cement Association. When a siphon chamber is not required, the tank may be constructed according to dimensions, A, B, C, and F. For tanks having a VU Plan of tank with siphon. Cross section of tank with Cross section of siphon. single chamber tank. Fie. 1381.— Diagrams of septic tanks. capacity of 750 gal. or less, 3-in. siphons are suitable, and 4-in. siphons are required for the larger tanks. DIMENSIONS OF Septic TANKS Dimensions Suggested length of Maximum tile system number of | Capacity yi B C D E F persons in gallons Paes. served bi & i g e 8 ie g y g S Open Tight e S ® S 2 S 2 S ® g % | soil, feet | soil, feet les) Pel ee | Ble tl elie |] ee Be 5 250 2 4|...| 6 Zed ale One L 150 250 10 500 3 5| 41] 5 BY Ie cca) kobe al 300 500 15 750 Selon son tLOn eS By Meter) PA es al 450 750 20 1000 SMe A harsl 5) oy KOM ter ae al 600 1000 25 1250 4/6/9 5 be Siadl pei toy ah 750 1250 Problems.—Construct a septic tank of the size selected by the instructor. Compute materials required; excavate, build forms, and make and place the concrete. Concrete plank for the cover may be made above ground, and placed when the interior forms of the tanks are removed. JOB 95. CONCRETE STEPS Practically every home needs one or more flights of concrete steps, either leading from the basement or from the front and rear entrances, or connecting one walk with another. Concrete steps, when well constructed, are firm, durable, safe, and sanitary. Forms for steps are usually of wood. For the side forms, 2-in. 268 CONCRETE PRACTICE plank should be used, and 1-in. material is usually satisfactory for braces and forms for risers. When desired, the forms for risers may be made to cause recessed panels in the risers. Forms for steps must be securely staked or otherwise fastened so as to be reasonably rigid. The form surfaces which come in contact with the concrete should be well oiled or thoroughly wetted a short time before the concrete is placed. The earth forming the subbase should be thoroughly and uni- formly tamped and compacted. Drainage must be provided, either by drain tile or a layer of porous material, such as cinders, if there is a reasonable chance of water collecting under the steps. 1x4" Supports For Pee ene Wall Fia. 1382.—Forms and section of concrete steps. In general, the concrete mix and consistency used for concrete steps should be the same as that used for the construction of concrete sidewalks. For separate flights of steps, a 1:2:3 mix by volume is recommended. The thickness of the steps at any point should not be less than 6 in. Figure 132 shows the method of construction of concrete basement steps. Side walls for steps in concrete walks may be provided or not, as desired. The methods of mixing, placing, finishing, and curing of con- crete for concrete sidewalks should be followed when making concrete steps. Wood floats should be used for finishing, as steel tools may make the surface too slippery. Steel tools are necessary for edging and rounding corners, ete. ta is FIELD WORK 269 Forms may be removed after a few days. The steps should be covered for a day with wet canvas or burlap, and then kept wet for a week so that the concrete can ‘‘cure”’ and “‘harden”’ in the presence of moisture. Problems.—Construct a flight of steps as directed by the instructor. Compute materials needed, excavate and compact subbase, construct forms, mix, place, and finish concrete, cure concrete, and remove forms. JOB 96. CONCRETE WINDOW SILLS AND LINTELS Precast concrete window sills and lintels have often been used instead of cut stone sills and lintels, and with satisfactory results in regard to labor required and appearance of the finished work. In general, precast sills and lintels are more economical than those cast in place in the walls. | There are two kinds of sills and lintels, those made in one section and those made in two sections. When the sill or lintel does not extend clear through the wall, and is not to have room plaster applied directly to one side of it, the one-piece lintel: is satisfactory. A one-piece sill or lintel must be furred out for the lath and plaster, because otherwise water may pass through the concrete and show on the plaster. The two-piece sill or lintel is one constructed in two sections, with an air space provided between the sections. This air space is necessary to prevent the passage of water through the concrete, or the condensation of water on the inside surfaces. The width of the air space may be 14-in. or more, and the space must be continuous. Both sections of a lintel should prefer- ably be of the same size or about the same size. Lintels should be reinforced, so that they can properly carry the loads that will be applied to them. At least two reinforcing bars should be used for each lintel (one bar for each section, if the lintel is in two parts). In general, the cross-sectional area of the reinforcement should be from about 34 of 1 per cent to 1 per cent of the cross-sectional area of the lintel. When placing lintels in walls, the reinforced side must be the lower one, that is, the reinforcement must be in the bottom of the lintel. As the sills do not carry any appreciable load, they do not need to be reinforced, except, possibly, to reduce the chance of 270 CONCRETE PRACTICE breaking them in handling. A 14-in. round bar placed about 1 in. from each corner of the sill will usually be sufficient. The table which follows gives the reinforcement needed for lintels of various heights and used in different stories of the building. This table may be used for designing lintels for residences and ordinary store buildings, up to two stories and basement in height. For one-story houses, the first-story values may be used for the basement lintels, and the second-story values for the first-story lintels. For warehouses, larger and higher buildings than two story residences, and buildings sub- jected to heavy loadings, the design of the lintels should be left to the concrete-designing engineer. NUMBER AND SIzE OF RounpD Bars REQUIRED FOR REINFORCING LINTELS OVER Doors AND WINDOWS Basement | | First story | Second story Height of lintel in inches eee 6 to 9 | 9 to 12 6 to 8 | 9 to 12 6 to 8 | 9 to 12 opening in inches Number and size of bars Num- Nu : Num ele Ni : Num . | Num i i Size ee Size ees Size ee Size ie Size en Size 0-28 3 16 2 14 2 16 2 34 2 3¢ 2 36 28-36 2 54 2 4 2 4 2 3g 2 36 2 | 3% 36-48 2 34 2 | 54 BA Se 2 16 2) 4 Pa ee a 48-60 2 4% 2 34 2 34 2 56 2 58 2 44 60-72 3 as ee Fea oe | 2 1% 29S. 2. | 34 Notre.—Two bars are to be used for each lintel. Place one bar in each section of a two-piece lintel. Bars should be embedded 34 in.. from the lower side of the lintel as placed in the wall. The forms for concrete sills or lintels may be made either of metal or wood. Metal forms are satisfactory when a large number of sills or lintels of the same size are to bemade. Wooden forms are usually more satisfactory when a variety of sizes and only a few sills or lintels of each size are wanted. Glue, plaster, or sand molds may be used for making ornamental sills and lin- tels, as in making ornamental trim stone. Wooden molds may be kept from swelling and warping by giving them one or two FIELD WORK 271 coats of shellac or linseed oil. Just before the concrete is placed, the form surfaces should be given a thin coating of form oil, to keep the concrete from sticking to the forms. Almost any clear oil that will give a thin oil film which will not stain the concrete will be satisfactory. Forms should be designed so that they can be easily assembled and taken apart. The various form pieces should be of the exact size and shape required, and should fit together in such a manner that they may be easily pulled away from the concrete without injuring the surfaces or edges of the sill or lintel. When desired, sills and lintels may be made with special sur- _ face finishes or facings, according to methods described in See. II. The proportions of the mix for concrete for sills and lintels should be about 1:2:3 by volume. Fine aggregates should all pass the No. 4 sieve, and not over 5 per cent should pass the No. 100 sieve. Coarse aggregates should all pass the 34-in. sieve, and not over 5 per cent should pass the No. 4 sieve. As little mixing water should be used as will give a workable mix. Con- crete should be thoroughly tamped and worked in the forms to give the surfaces desired, free from voids and pockets. The amount of hair cracks and crazing may be reduced by avoiding an excess of fine material (cement, stone dust, silt), by using as little mixing water as necessary, by placing and finishing the concrete so that a film of water and fine material will not be left on the surface, by not using steel finishing tools, if possible, and by keeping the concrete surfaces wet for about 1 week or 10 days after the concrete is placed. Problems.—Estimate the materials required for forms and concrete, construct forms, and make some window sills and lintels according to the sizes and designs given by the instructor. Note labor required. Com- pute complete costs per cubic foot of concrete placed and per sill or lintel made. JOB 97. PLAIN CONCRETE FLOORS In this job, the construction of plain concrete floors laid on the ground is considered. Such floors are suitable for basement floors, barn floors, small garage floors, etc. The following condensed specifications are for plain concrete floors, which are to be subjected to light and moderate traffic. 272 CONCRETE PRACTICE They may seem to be a little severe for basement floors for resi- dences. ‘These specifications are similar to the American Concrete Institute Tentative Standard Specifications for Concrete Floors. Condensed Specifications for Plain Concrete Floors Laid on the Ground and Suitable for Moderate or Light Traffic General Requirements Portland Cement.—Shall meet the requirements of the Standard ges fications for Portland Cement as given in Appendix 1. Fine Aggregate.—Shall consist of natural sand or screenings from hard, tough, crushed rock or gravel consisting of quartz grains or other hard material clean and free from any surface film or coating, graded from fine to coarse with coarse particles predominating. Dry fine aggregate shall all pass a No. 4 sieve, not more than 25 per cent shall pass a No. 50 sieve, and not more than 5 per cent shall pass a No. 100 sieve. Percentage of silt, clay, or loam shall not be more than 5 per cent. Tensile strengthof 1:3 mortar briquettes should be equal to, or more than, that of standard Ottawa sand briquettes of the same mix and consistency. Course Aggregate.—Shall consist of clean, hard, tough, uncoated crushed rock or gravel containing no soft, flat, and elongated particles, and being free from vegetable and organic matter. All coarse aggregate shall be well graded, and shall pass a 114-in. sieve, and not more than 5 per cent shall pass a No. 4 sieve. No. 1 Aggregate for Wearing Courses.—Shall be of equal quality as coarse aggregate. All No. 1 aggregate when dry shall pass a 3-in. sieve, and not more than 10 per cent shall pass a No. 4 sieve. Water.—Shall be clean and fit to drink. Reinforcement.—Should in general meet the requirements of the Stand- ard Specifications for Steel Reinforcement of the A. 8. T. M. Joint Filler.—Should be a suitable compound which will not soften and run in hot weather or pone or crack in cold weather, or premolded strips of bituminous-filled fiber 1¢-in. thick, and of a width equal to the thickness of the floor slab. Measuring.—Shall be such as will insure uniform proportions and con- sistency at all times. Mixing.—Concrete shall be mixed until each particle of fine aggregate is coated with cement paste, and each particle of coarse aggregate is coated with mortar. A batch mixer is preferred for mixing. Retempering.—Retempering or remixing mortar or concrete that has partially hardened shall not be permitted. Curing.—A freshly finished concrete floor shall be protected from the sun, wind, and rain until it can be sprinkled and covered. As soon as the finished floor has hardened sufficiently, it shall be covered with an inch of wet sand or 2 in. of wet Sawdust, and kept wet by sprinkling with water for at least 10 days. FIELD WORK 273 Subgrade.—Shall be well drained and compacted to a firm surface with a uniform bearing power. All soft and spongy places shall be removed and filled with suitable material well tamped. A drainage system shall be provided when necessary. Subbase.—When required, only clean coarse gravel or steam-boiler cinders free from ash and unburned coal shall be used. Thickness of sub- base shall be at least 5 in. Subbase shall be thoroughly compacted and wetted before the concrete is deposited. Forms.—Shall be free from warp, and of sufficient strength and rigidity. Shall be well staked or braced and held to established lines and grades, and their upper edges shall conform to the established grades of the floor. Forms shall be cleaned and thoroughly wetted or oiled before concrete is deposited. Size and Thickness of Slabs.—The floor slabs shall be independently divided concrete block having an area not more than 100 sq. ft., or dimen- sions greater than 10 ft. If larger areas are required, the slabs must be specially reinforced. ‘The thickness of the floor slab should not be less than 5in. Thickness selected depends upon the loads, subbase, and strength of mix. Joints.—When required, }4-in. joints shall be left between the slab and walls and columns of the building. Edges.—Unless protected by metal, edges of slabs should be rounded to a radius of 4 in. Consistency.—The least amount of mixing water that will give a work- able mix shall be used for concrete and mortar mixes. Reinforcement.—Slabs having an area of more than 100 sq. ft. or dimen- sions greater than 10 ft. shall be reinforced with wire fabric, or with plain and deformed bars. The reinforcement shall weigh not less than 28 lb. per 100 sq. ft. of floor surface. The reinforcement shall be placed upon, and slightly pressed into, the concrete base immediately after the base is placed. It shall not cross joints, and shall be lapped sufficiently to develop the full strength of the metal. Two-course Plain Concrete Floors Proportions for Base Course.—The concrete shall be mixed in the pro- portions by volume of one sack of portland cement, 24 cu. ft. of fine aggre- gate, and 5 cu. ft. of coarse aggregate. Placing Base Course.—After mixing, the concrete shall be handled rapidly and the successive batches deposited in a continuous operation, completing individual sections of the required depth and width. Under no circumstances shall concrete that has partly hardened be used. The forms shall be filled, and the concrete struck off and tamped to a surface, the thickness of the wearing course below the established elevation of the floor. The method of placing the various sections shall be such as to pro- duce a straight, clean-cut joint between them, so as to make each section an independent unit. If dirt, sand or dust collects on the base it shall be removed before the wearing course is applied. Workmen shall not be 274 CONCRETE PRACTICE permitted to walk on the freshly laid concrete. Any concrete in excess of that needed to complete a section at the stopping of work shall not be used. In no ease shall concrete be deposited upon a frozen subgrade or subbase. Proportions for Mixture No. 1 for Wearing Course.—The wearing course shall be mixed in the proportions of one sack of portland cement and 2 cu. ft. of fine aggregate. The minimum thickness shall be 34 in. Proportions for Mixture No. 2 for Wearing Course.—The wearing course shall be mixed in the proportions of one sack of portland cement and one cubic foot of fine aggregate and one cubic foot of No. 1 aggregate. The minimum thickness shall be 34 in. Mortar Consistency for Wearing Course.—The mortar shall be of the driest consistency possible to work with a sawing motion of the strikeboard. Placing Wearing Course.—The wearing course shall be placed immedi- ately after mixing. It shall be deposited on the fresh concrete of the base before the latter has appreciably hardened, and brought to the established grade with a strikeboard. In no case shall more than forty-five minutes elapse between the time the concrete for the base is mixed and the wearing course is placed. Finishing Wearing Course.—After the wearing course has been brought to the established grade by means of a strikeboard, it shall be worked with a wood float in a manner which will thoroughly compact it and provide a surface free from depressions or irregularities of any kind. When required, the surface shall be steel-troweled, but excessive working shall be avoided. A mixture of dry cement, sand and No. 1 aggregate may be applied to the fresh concrete of the base for a wearing course, but in no case shall dry cement or a mixture of dry cement and sand be sprinkled on the surface of the wearing course to absorb moisture or to hasten the hardening. Special methods not conflicting with these specifications may be used. Coloring.—If artificial coloring is employed, only mineral coloring matter shall be used, and it must be incorporated with the entire wearing course, and shall be mixed dry with the cement and aggregate until the mixture is of a uniform color. In no case shall the amount of coloring exceed 5 per cent of the weight of the cement. One-course Plain Concrete Floors Proportions.—The concrete shall be mixed in the proportions of one sack of portland cement to not more than 2 cu. ft. of fine aggregate and not more than 3 cu. ft. of coarse aggregate, and in no case shall the volume of the fine aggregate be less than one-half the volume of the coarse aggregate. A cubic yard of concrete in place shall contain not less than 6.8 cu. ft. of cement. Placing.—(This is the same as for placing base course of two-course floors. ) Finishing.—After the concrete has been brought to the established grade by means of a strike board, and has hardened somewhat, but is still work- able, it shall be floated with a wood float in a manner which will thoroughly compact it and provide an.even surface. When required, the surface shall FIELD WORK 275 be steel troweled, but excessive working shall be avoided. Unless pro- tected by metal, the surface edges of all slabs shall be rounded 14 in. When desired, a terrazzo floor finish may be applied to any concrete floor. A concrete floor surface may be made satisfactory for dancing by applying liquid soap and rubbing this soap into the pores of the concrete with a scrubbing brush. An application of pow- dered soap to a treated floor helps to keep-it in condition. Another method is to apply paraffin wax, dissolved in turpentine, in sufficient quantity to fill the pores of the concrete. After the turpentine has evaporated and the floor surface is dry, powdered wax should be applied as in the case of a wooden floor. There are various methods of treating concrete surfaces, which have been previously described in the text. When desired, most any of these methods may be used for treating concrete floor surfaces. Problems.—a. Observe the construction of a concrete floor, noting preparation of subgrade and subbase, forms, dimensions and thickness of concrete slab, one- or two-course floor, proportions of mix, consistency, concrete plant, reinforcement, mixing, placing, finishing, curing, etc. Note organization of crew and labor hours required for each part of the work. b. Construct a one-course concrete floor as directed by the instructor: (1) preparing a complete estimate of all materials, plant, and labor needed; (2) preparing the subgrade, subbase, and forms; (3) mixing, placing, and finishing the concrete; and (4) curing the concrete. Keep records of all materials and labor used. JOB 98. CONCRETE CULVERTS—SPECIFICATIONS AND ESTIMATES Concrete culverts are of three kinds: pipe, box, and arch. Pipe culverts are usually the most economical for small areas, while box and arch culverts are needed for larger areas. The selection of a culvert depends upon the size and character of the drainage area, available head room, depth of fill, kind of foundation, and the opinion of the person selecting the culvert. Sometimes box and arch culverts are built without a floor, and are called open-box or open-arch culverts. The present practice is to provide concrete floors for all concrete culverts unless the natural bed or floor should happen to be of comparatively hard 276 CONCRETE PRACTICE bedrock, so that the side walls will not be undermined by water. A culvert, in order to be efficient, should have the same general direction as the flow of the stream; the bottom of the culvert should be lower at the discharge end than at the head end; the slope or inclination of the culvert bed should be about the same as that of the stream; the head walls or wings should be arranged to help the flow of the water; and there should be no projections in the culvert bed or obstructions near the entrance or discharge ends which would interfere with, and reduce, the free flow of the water. In general, the culverts should be placed across road- ways and in the direction of the stream flow. The size of the waterway or the culvert cross-sectional area required depends upon the maximum rate of rainfall, area and shape of the watershed, kind and condition of the soil, and the character and slope of the drainage surface and stream bed. The best way of determining the culvert area needed is to observe the flow of the stream during flood times, and to measure the cross-section of the stream at some narrow place near the culvert site. When stream data is not available or reliable Talbot’s formula may be used for finding the required culvert area. This formula Lee A = Cw/D3 where A = area of waterway in square feet D = drainage area in acres C =a coefficient, depending on the character of the drainage area C varies from 24 to 1 for steep and rocky ground; it equals about 14 for rolling agricultural country subject to floods due to melting of snow, and with a valley length of three to four times its width; and equals about 1, or less, in localities not affected by floods due to melting snow, or where the valley length is many times the width. C should be increased for steep side slopes, especially when the upper part of the valley is much steeper than the channel near the culvert. The following table gives the area of waterway required for various drainage areas: a FIELD WORK Bit WATERWAY OR CULVERT AREA REQUIRED eteste area in Steep slopes Rolling country Flat country aaa Culvert area in square feet 10 5.6 1.9 1.1 20 9.4 3.1 1.9 30 12.8 4.3 2.6 40 16.0 5.3 one 50 19.0 6.3 3.8 60 21-5 fas 4.3 80 at 9.0 5.4 100 a2 1025 6.3 125 ol 12,5 fee 150 43 14.5 8.6 200 aps 18 10.5 300 fie. 24 15 400 89 30 18 600 121 40 24 800 150 50 30 1000 178 59 36 The length of the culvert. will depend upon the width of the roadway and the depth of fill on top of the culvert. The slope of the earth fill can usually be taken as one and one-half horizon- tal to one vertical. In highway construction, the width of road- way should not be decreased at a culvert, as such practice is dangerous. Head walls and wings should be built so that the embankment is protected and the flow of the water aided. These wings may be placed parallel with, or at right angles to, or inclined (usually 30 to 45 deg.) with, the axis of the culvert. Wings parallel to the roadway are often used for small culverts with low fills, and the wing walls are built up above the grade line to provide a guard rail. Flared wings are better on deeper fills, as these wings facilitate the flow of water and are economical in the amount of concrete required. Wings parallel to the axis of the culvert are sometimes used when the culvert is likely to be made longer in the near future. In general, the head walls and wings should be long enough to keep the culvert opening clear when earth falls around the ends. CONCRETE PRACTICE 278 a “UOISSTUIMIOZT) ABMYSIFT UISUOOST MA —}IOA[ND XOq 9}OIDTON— EET ‘DIT "“Sdiolf{y ‘oD : : poe dyn hie Of [foe Jyp pro g2 yyteg 22a LX %e B Was {79 AYE . . worsspuiweg Komybyy 241M Of, UYIM pau Kyeunzas oq [Joys Pua ayrbuEldy eo yim sobpa posodx? 42 faA2g Ze G24 2 ; UISLIOIEIY JO CUOYOUyIzIde pumpuofe po2jde 212M Siojlwolp Op dy joys 610g suoysodord “OSIM NOSIOWN P2yis2d’ exmssyo s62/UN pus abaoyocip ‘Su0g puog jo2UeyzaU P2UWdefyP — 7: 2:]-_ SELL 27 [JOYS 24212009 /// NOISSINWOD AVMHDIH NISHOISIM 22% 102) “20 qour F jasiag adoe auonbs, 2 eg (fous puausazsejuied //¥ ‘bumesp sity 7028. you OG STIVMGN] SNIdOTS :SFLON TWYINTD LY3SATIND XOB 3LSYDNOD ZX oes auvonwis ' OMPOOY WOULWAFTFI DNF - Os See . 4 NOWLWAFTT FUEF | ZB WHO MOMLITS ISUVSWWUL FZ i PPS H O) @) ie 22unftig| A2/7 HO ; =f/// a “FA | Pr? | 14a | am ee ees ee my 44 Ol= Med preg | su2ue7 | 2/2131009 | e WM).I5/ 1.67 | + | oo] PY SUM) .D-/ [Ese | PF | Fy _| peuipryeT FL\,O- | |_| Reet 3 | i PY PART «EGR DMISOINIFTS SO THT Ce ———— swe2nde log 2yyopoll PeAO4CAD {IM HOR) on Files Se = pxeoddns Ky4edo4d 2q of yvaUussrdojiulasy LYIAMID TINS IO HTS F INFINFISOINIFAY AOL IO WH Id € FIELD WORK 279 Pipe culverts of cast iron, corrugated iron, vitrified clay, and plain and reinforced concrete are suitable in many places. Cor- rugated iron for small pipe culverts and reinforced concrete pipe for the larger sizes seem to be preferred at present. All pipe culverts should have concrete head walls to protect the embank- ments and the ends of the culverts. Reinforced concrete pipes up to about 6 ft. in diameter have been used. Concrete box and arch culverts of many types have been designed and used. Most every State Highway Commission and Railroad Company has its own set of standards for these kinds of culverts. The design of a box or arch culvert depends upon the foundation conditions, depth and character of the soil, and loadings to be applied. Culverts of more than 6-ft. span are frequently classified as bridges. Figure 133 shows a standard design of a concrete box culvert with sloping end walls prepared by the engineers of the Wisconsin Highway Commission. Specifications for concrete materials and for concrete for plain and reinforced concrete culverts vary in different localities. The specifications of the Wisconsin Highway Commission for Concrete in forms given in Job 36, are typical. Clauses not applying to the particular job are omitted or crossed out. Class A concrete is preferred for the standard concrete box culverts. Forms for culverts are often constructed of 2-in. plank, well supported, braced, and tied in place. Forms for the interior of a box culvert should be so made that they can be readily removed without damage to the concrete. Wedged braces may be used, with the wedges so made and placed that they can be readily removed. The concrete should be allowed to cure or harden for at least 3 weeks in hot weather, or longer in cold weather, before the forms are removed. Exposed concrete surfaces should be pro- tected from the rays of the sun and dry winds during the curing period. When practicable, the exposed surfaces should be covered with damp sand and kept wet for 1 week or 10 days after the concrete has attained initial set. If a surface covering is not practicable, then the concrete should be sprinkled twice a day. Problems.—Prepare the materials estimate for the Wisconsin Highway Commission Concrete Box Culvert shown in Fig. 133, assuming an 18-ft. 280 CONCRETE PRACTICE roadway and a fill of 6 ft. over the top of the culvert. Estimate excavation, forms, reinforcement, cement, sand, and crushed rock, assuming Class A concrete. If an actual culvert is to be constructed, the roadway width, fill, culvert length, etc., in this job should be changed to conform with those for the culvert to be built. Prepare an estimate of the labor required for this culvert, subdividing the estimate as follows: excavation, forms, bending and placing reinforce- ment, mixing and placing concrete, removal of forms, and backfilling. JOB 99. CONCRETE BOX CULVERTS—EXCAVATION AND STAKING OUT The best way is to stake out and construct the culvert before the fill is placed. When the fill is already in place, the dirt must be excavated to the bottom of the culvert floor. The bottom of the excavation should be true to grade and alignment. All soft and spongy places in the soil should be removed and replaced with good earth, well tamped to give a uniform bearing power. It is important that the dirt forming the subgrade be firm and compact to give a uniform bearing power. ‘Trenches for the cut- off walls at each end of the culvert must be dug. The slope of the excavation should be such that there will be no trouble due to dirt sliding down on the subbase, or into the forms. In staking out a culvert, stakes are driven to give the elevation, slope, or grade and alignment of the top of the culvert floor, as well as the general overall dimensions of the culvert. In general, the culvert will extend crosswise of the roadway, and its align- ment and slope will conform to that of the waterway. Care should be taken not to have the culvert floor too far above or below the bed of the waterway, or too far out of alignment so as to obstruct the flow of water, or to reverse the slope of the culvert floor. This slope should preferably not be less than 14 in. to the foot. A convenient bench mark and reference stakes (offset a given distance to the side of the center line of the culvert) should be provided for the purpose of checking the elevation and slope of the culvert floor. Problems.—a. Observe the staking out of a culvert, noting just what stakes are set, how they are set, and where. b. Stake out a culvert. This culvert may be assumed to be placed under an existing roadway, or to be for a proposed new roadway. An engineer’s level, level rod, and measuring tape should be used if available. Satisfactory work may be donewith a good carpenter’s level, straightedge, and measuring | : ; FIELD WORK 281 tape, if engineering instruments are not to be had. Draw a sketch showing location of the roadway and all stakes set. If any excavating is needed, this should be done, noting quantity of dirt removed and labor hours required. JOB 100. CONCRETE BOX CULVERTS—FORMS AND REINFORCE- MENT The forms used for large concrete culverts are usually of 2-in. plank well braced and tied. For smaller culverts, 1-in. boards SW Fia. 135.—Forms for 10 X 10 ft. reinforced concrete box culvert, C. B. & Q. Ry. may be used, if they are supported and held in place by cross- braces placed fairly close together. Figures 134 and 135 should be examined for details of culvert forms. 282 CONCRETE PRACTICE Care should be taken in the design of the forms so that they will be firm and unyielding, and yet be economical in regard to lumber and be easy to remove. Wedges, with the braces of the inside forms of a box culvert, aid in making these forms easy to remove. The reinforcement bars should be carefully placed in position and wired together, so that they will not be displaced during concreting. Problems.—a. Observe the construction of forms for a concrete box culvert, noting size and dimensions of the culvert, amount, kind, and dimen- sions of form lumber used for different parts of the forms, ties, braces, wedges, etc. Make sketches of the forms, if these sketches will help illus- trate and explain the form construction. Note labor hours required, and number of square feet of form surface. Observe how the reinforcing rods are placed and secured in position. b. Make a bill of material for the form lumber. Make sketches for the design of the form, if such sketches are needed. Construct the form for the culvert staked out in the preceding jobs, noting labor hours required. Place reinforcement bars in forms and secure them in position, noting labor hours required. JOB 101. CONCRETE BOX CULVERTS—CONCRETING Before starting concreting, the materials should be on the job, and the plant clean and in working order. Sometimes the mixer can be placed high enough above the culvert forms so that the concrete can be chuted into the forms. - Usually runways and barrows or carts are used for transporting concrete. The concrete is poured monolithic up to the construction joint, then the inside forms and the reinforcement bars for the top of the culvert are placed in position and the concreting finished. These inside forms should be previously prepared, so that they can be placed without appreciably interrupting the process of concreting. With good planning, the delay in concreting should not be over 20 or 30 min. If more than 45 min. are required for the placing of the inside forms, the concrete surface at the construction joint should be roughened, cleaned of all loose concrete material, debris, and laitance, and a coat of cement grout applied before any new concrete is placed. As the concrete is placed in the forms, it should be spaded so as to push the large aggregate away from the form surfaces and LF >. ee FIELD WORK 283 to remove air pockets. A little tamping may be advisable thoroughly to compact the concrete in place. All exposed edges should be rounded, and the exposed surfaces of the concrete should be finished when the concrete is placed. Problems.—a. Observe the concreting of a concrete box culvert, noting the plant layout, organization of crew, method of placing concrete, amount of concrete placed, and time required. b. Arrange the plant, organize crew, and mix and place concrete in the concrete box culvert forms constructed in the previous job. Note amount of concrete placed and labor hours required. JOB 102. CONCRETE BOX CULVERTS—REMOVING FORMS After the concrete has hardened, the forms should be removed in such a manner that the concrete will not be damaged. Con- crete should be from 14 to 28 days old in warm weather, and older in cold weather, before the forms are removed. After the forms are removed, the concrete surfaces should be gone over, fins and projections removed, and holes and spongy places dug out and patched. The form lumber removed should be separated, nails removed, surfaces cleaned, and then piled for removal to another job. The backfilling should now be done. The dirt should be placed in layers about 6 in. thick, and each layer tamped and compacted before the succeeding layer is placed. If a supply of water is available, thoroughly wetting the backfill will help settle the dirt. Problems.—a. Observe the removal of forms, concrete surface cleaning and repairing, and backfill on a concrete box culvert Job, noting amount of work done and labor hours required. b. When the concrete of the box culvert made in previous jobs is 3 weeks old, remove the forms, and separate, clean, and pile the lumber; clean and patch concrete surfaces; and make all needed backfill, noting amount of work of each kind and labor hours required. ~JOB103. CONSTRUCTION OF REINFORCED CONCRETE BUILDINGS The successful and economical construction of a reinforced concrete building requires very careful planning in regard to plant, forms, labor, rate of progress, and other construction details. As a building is larger and more complicated in detail than most of the structures described in previous jobs, the profit- 284 CONCRETE PRACTICE able construction of the building will, consequently, require much more care and thought. The estimates for plant, materials, labor, and costs should be carefully made according to the principles given in Sec. IV. The correct planning of the work is important. The prepara- tion and use of progress charts, work schedules, and material schedules are almost a necessity on large jobs, and are an aid on smaller and medium-sized jobs. The choice of plant, plant layout, materials storage, and simi- lar items must be carefully thought out in advance. Sketches for the plant layout should be prepared on all large jobs. The excavation for the basement will usually be made according to the methods already given, except that trucks with a steam or gas shovel or drag line will probably be used on largejobs. Inmany instances, the walls of the excavation will need to be braced. A pump may be required for the removal of ground water. In special cases, it may be necessary to , shore up or underpin the walls of adja- Fic. 136.—Isolated footing. cant buildings. After the excavation is completed, the building foundations are constructed. ‘These foundations may be in the form of separate or isolated footings for each of the columns and walls; combined footings (including the so-called cantilever footings), when one or more columns are carried by one footing; continu- ous footings, when the footing is continuous under a row of columns; and raft footings, which extend over the whole lot, support all columns, and are built monolithic. Raft footings are frequently used when the soil has but comparatively low support- ing power. Piles are used under the footings when so required by soil conditions. Concrete footings (either plain or reinforced) appear to be the most economical at the present time. The formwork; steel bending and placing, and pouring of concrete for the foundations rarely cause any trouble. Location or key plans showing the location of columns and beams are almost necessary on all reinforced concrete building Neen s/eps outsive This Outline for gsteped | Ashped footing | footing FIELD WORK 285 SB EREOM ¥ Fig. 137.—Combined footing. Wa S NAL (GAY _Ik ir MH REY bF"2; gf? ‘ Neer Note.- Heavy dot and dash lines indicate stee/ in fop dak Heavy dotted lines indicate steel ip bottom Fic. 138.—Raft foundation. 286 CONCRETE PRACTICE jobs. i Fifth |_| floor NINE STORIES re--neree neers ons eederessoe~ H Hy : ff 3 acces nanene nae be mene ness cet eees 0 cewek: sedessesaseus mere T EN, STORI eS wm aeed samst oes badesosss 3 #7009 be aor sg tf eee . ‘ FLAT SLAB CONSTRUCTION BEAM AND GIRDER CONSTRUCTION Fig. 142.—Cross sections of reinforced concrete buildings. 288 CONCRETE PRACTICE The concrete mixes used are invariably given in the plans and specifications. Mixes are usually proportioned to give a 28-day unit compressive strength of 2000 lb. per sq. in. or greater. Columns are usually poured up to the bottom of the column capital and allowed to set 24 hr. before pouring the capital and floor slab. Whenever practicable, the column capitals and floor slabs and beams for any one floor should be poured in a single operation. Forms should not be removed too soon, especially in cold weather. In general, the beam and floor-slab forms should be designed and built so that they may be removed without dis- turbing some of the props or shores which support the beams and slabs. Props should not be removed until it is certain that the concrete has hardened and attained enough strength easily to carry the loads placed upon it. After the forms are removed, all fins and other projections should be removed, porous places cut out and patched when necessary, and the exposed concrete surfaces finished as required in the plans and specifications. In most commercial and factory buildings, a cement floor finish is usually applied integral with the floor slab. In some instances, the cement floor finish is applied after the floor slab has hardened. Some other types of finish commonly used are terrazzo, tile, asphalt, linoleum, brick, steel plates (for trucking aisles), wood block set in asphalt, and various types of wood floors. Tile floors are commonly used in entrances, corridors, lobbies, vestibules, and toilets. Asphalt floors are suitable where water- proof floors are desired. Brick and wood block floors are suit- able where heavy trucking occurs. Finished wood floors of oak, maple, or birch are often desired. Sleepers (about 2 X 3 in. in size and placed 16-in. on centers) are set on, and anchored to the floor slab. A layer of waterproof building paper is placed on top of the sleepers, and then the finished flooring is laid. Sometimes the space between the sleepers is filled with lean cinder concrete. Floor coverings, such as linoleum, are suitable for offices, corri- — dors, schoolrooms, ete. Various types of roofings have been used for reinforced concrete buildings. A cement-finish roof surface is satisfactory when absolute dryness is not required. Cement roof finishes tend to FIELD WORK 289 erack in time, and thus cause small leaks. An asphalt coating, using asphalt with a high melting point, gives fairly satisfactory service, but must be renewed every year or so. The same is true of special roof paints. | APPENDICES o}H0g 3 ‘unig doy A "OHIO" zg! JPAs]-pUDj{sLO) \. Sass a 43 YI = Cage e 3 Sg TO 499NDY aes vila g 7. = N ‘S s “UDG woa}yog [ABT 4uUD{SUOD pe : : a Boreas : “1... sabuy saddon Away ---~ -- palapjo> 4a Badly 2 - buoy, auyp uasy, 2 aay uay 2 SE Noy uU LS f Bi Of--" = 0 pausing ADP] Aol *41dA0N) 40 SUOILOAD[Z 9 A A ad of =. &, ao S Phctiaettl aad CONCRETE PRACTICE 314 WOI}VID9UISICT O1}104SIC, *480} SSOUPUNOS UI soIN]Iej [RoIdA],—F “D1q suryoey BUHIVID eseyUuLYg Tom APPENDICES 315 46. Vicat Apparatus. The time of setting shall be determined with the Vicat apparatus described in Sec. 38. (See Fig. 2.) TaBLE I.—PEROCENTAGE OF WATER FOR STANDARD MorTARS i Percentage of Percentage of Percentage of Percentage of water for neat water for one water for neat water for one cement paste of cement, three cement paste of cement, three normal consist- | standard Ottawa || normal consist- | standard Ottawa ency sand ency sand 15 9.0 23 10.3 16 9.2 24 10.5 17 9.3 25 Sieg 18 9.5 26 10.8 19 9.7 27 11.0 20 9.8 28 11.2 21 10.0 29 nD em 22 1022 30 Le 47. Vicat Method. A paste of normal consistency shall be molded in the hard-rubber ring G as described in Sec. 39, and placed under the rod B, the smaller end of which shall then be carefully brought in contact with the surface of the paste, and the rod quickly released. The initial set shall be said to have occurred when the needle ceases to pass a point 5 mm. above the glass plate in 14 min. after being released; and the final set, when the needle does not sink visibly into the paste. The test pieces shall be kept in moist air during the test. This may be accomplished by placing them on a rack over water contained in a pan and covered by a damp cloth, kept from contact with them by means of a wire screen; or they may be stored in a moist closet. Care shall be taken to keep the needle clean, as the collection of cement on the sides of the needle retards the penetration, while cement on the point may increase the penetration. The time of setting is affected not only by the percentage and temperature of the water used and the amount of kneading the paste receives, but by the temperature and humidity of the air, and its determination is therefore only approximate. 48. Gillmore Needles. The time of setting shall be determined by the Gillmore needles. The Gillmore needles should preferably be mounted as shown in Fig. 5 (b). 49. Gillmore Method. The time of setting shall be determined as follows: A pat of neat cement paste about 3 in. in diameter and 4 in. in thickness with a flat top (Fig. 5 (a)) mixed to a normal consistency, shall be kept in moist air at a temperature maintained as nearly as practicable at 21°C. (70°F.). The cement shall be considered to have acquired its initial set when the pat will bear, without appreciable indentation, the Gillmore needle, 14 in. in diameter, loaded to weigh 44 lb. The final set has been acquired when the pat will bear without appreciable indentation, the Gill- 316 CONCRETE PRACTICE more needle 144 in. in diameter, loaded to weigh 1 lb. In making the test, the needles shall be held in a vertical position and applied lightly to the surface of the pat. XIV. TENSION TESTS 50. Form of Test Piece. The form of test piece shown in Fig. 6 shall be used. The molds shall be made of non-corroding metal and have sufficient material in the sides to prevent spreading during molding. Gang molds (a) Pat with top surface flattened for determining time by Gillmore method. ee. Z (b) Gillmore needles. Fire: 5. when used shall be of the type shown in Fig. 7. Molds shall be wiped with an oily cloth before using. 51. Standard Sand. The sand to be used shall be natural sand from Ottawa, IIl., screened to pass a No. 20 sieve and retained on a No. 30 sieve. This sand may be obtained from the Ottawa Silica Co., at a cost of 3 ets. per lb., f.o.b. cars, Ottawa, Ill. 52. This sand, having passed the No. 20 sieve, shall be considered stand- ard when not more than 5 g. passes the No. 30 sieve after 1 min. continuous sieving of a 500-g. sample. 53. The sieves shall conform to the following specifications: APPENDICES 317 Fig. 7.—Gang mold. 318 CONCRETE PRACTICE The No. 20 sieve shall have between 19.5 and 20.5 wires per whole inch of the warp wires and between 19 and 21 wires per whole inch of the shoot wires. The diameter of the wire should be 0.0165 in. and the average diam- eter shall not be outside the limits of 0.0160 and 0.0170 in. The No. 30 sieve shall have between 29.5 and 30.5 wires per whole inch of the warp wires and between 28.5 and 31.5 wires per whole inch of the shoot wires. The diameter of the wire should be 0.0110 in. and the aver- age diameter shall not be outside the limits 0.0105 to 0.0115 in. 54. Molding. Immediately after mixing, the standard mortar shall be placed in the molds, pressed in firmly with the thumbs and smoothed off with a trowel without ramming. Additional mortar shall be heaped above the mold and smoothed off with a trowel; the trowel shall be drawn over the mold in such a manner as to exert a moderate pressure on the material. The mold shall then be turned over and the operation of heaping, thumbing, and smoothing off repeated. 55. Testing. Tests shall be made with any standard machine. The briquettes shall be tested as soon as they are removed from the water. The bearing surfaces of the clips and briquettes shall be free from grains of sand or dirt. The briqeuttes shall be carefully centered and the load applied continuously at the rate of 600 lb. per min. 56. Testing machines should be frequently calibrated in order to deter- mine their accuracy. 57. Faulty Briquettes. Briquettes that are manifestly faulty, or that give strengths differing more than 15 per cent from the average value of all test pieces made from the same sample and broken at the same period, shall not be considered in determining the tensile strength. XV. STORAGE OF TEST PIECES 58. Apparatus. The moist closet may consist of a soapstone, slate, or concrete box, or a wooden box lined with metal. If a wooden box is used, the interior should be covered with felt or broad wicking kept wet. The bottom of the moist closet should be covered with water. The interior of the closet should be provided with non-abosrbent shelves on which to place the test pieces, the shelves being so arranged that they may be with- drawn readily. 59. Methods. Unless otherwise specified, all test pieces, immediately after molding, shall be placed in the moist closet for from 20 to 24 hr. 60. The briquettes shall be kept in molds on glass plates in the moist closet for at least 20 hr. After from 20 to 24 hr. in moist air the briquettes shall be immersed in clean water in storage tanks of non-corroding material. 61. The air and water shall be maintained as nearly as practicable at a temperature of 21°C, (70°F.). APPENDICES 319 APPENDIX 2 STANDARD METHOD OF TEST _ FOR UNIT WEIGHT OF AGGREGATE FOR CONCRETE American Society for Testing Materials Serial Designation: C 29-21 This method is issued under the fixed designation C 29; the final number indicates the year of original adoption as standard, or, in the case of revi- sion, the year of last revision. PROPOSED AS TENTATIVE, 1920; ApoprEep, 1921 This method was approved May 29, 1923, as “Tentative American Standard” by the American Engineering Standards Committee 1. The unit weight of fine, coarse, or mixed aggregates for concrete shall be determined by the following method: 2. Apparatus. (a) The apparatus required consists of a cylindrical metal measure, a tamping rod, and a scale or balance, sensitive to 0.5 per cent of the weight of the sample to be weighed. (b) Measures.—The measure shall be of metal, preferably machined to accurate dimensions on the inside, cylindrical in form, water-tight, and of sufficient rigidity to retain its form under rough usage, with top and bottom true and even, and preferably provided with handles. The measure shall be of }40-, 4-, or 1-cu. ft. capacity, depending on the maximum diameter of the coarsest particles in the aggregate, and shall be of the following dimensions: : Inside Inside Minimum thick- | Diameter of lar- bapacity, diameter, | height, ness of metal, gest particles of A inches inches U. S. Gage aggregate, inches V9 6 6.10 No. 11 Under 4 Vy 10 11.00° No. 8 Under 144 1 14 11.23 No, “5” Over 144 (c) Tamping Rod.—The tamping rod shall be a straight metal rod 34 in. in diameter and 18 in. long, with one end tapered for a distance of 1 in. to a blunt bullet-shaped point. 320 CONCRETE PRACTICE 3. Calibrating the Measure. The measure shall be calibrated by accu- rately determining the weight of water at 16.7°C. (62°F.) required to fill it. The factor for any unit shall be obtained by dividing the unit weight of water at 16.7°C. (62°F.)! by the weight of water at 16.7°C. (62°F.) required to fill the measure. 4. The sample of aggregate shall be room dry and thoroughly mixed. 5. Method. (a) The measure shall be filled one-third full and the top leveled off with the fingers. The mass shall be tamped with the pointed end of the tamping rod twenty-five times, evenly distributed over the sur- face. The measure shall be filled two-thirds full and again tamped twenty- five times as before. The measure shall then be filled to overflowing, tamped twenty-five times, and the surplus aggregate struck off, using the tamping rod as a straightedge. In tamping the first layer the rod should not be permitted forcibly to strike the bottom of the measure. In tamping the second and final layers, only enough force to cause the tamping rod to penetrate the last layer of aggregate placed in the measure should be used. No effort should be made to fill holes left by the rod when the aggregate is damp. (b) The net weight of the aggregate in the measure shall be determined. The unit weight of the aggregate shall then be obtained by multiplying the net weight of the aggregate by the factor found as described in Sec. 3. 6. Accuracy. Results with the same sample should check within 1 per cent. APPENDIX 3 STANDARD METHOD OF TEST FOR SIEVE ANALYSIS OF AGGREGATES FOR CONCRETE American Society for Testing Materials Serial Designation: C 41-24 This method is issued under the fixed designation C 41; the final number indicates the year of original adoption as standard or, in the case of revision, the year of last revision. IssumD as TENTATIVE, 1921; ApopTED, 1922; REvIsED, 1924 1. Sampling. A representative test sample of the aggregate shall be selected by quartering or by use of a sampler, which after drying will give not less than the following: (a) Fine aggregate, 500 g. (b) Coarse aggregate, or a mixture of fine and coarse aggregates, weight in grams, 3000 times size of largest sieve required, measured in inches. 1 The unit weight of water at 16.7°C. (62°F.) is 62.355 Ib. per cu. ft. _ ; APPENDICES 321 TABLE | ert ea Sieve Wire Tol ' : : olerance, per cen _ Opening diameter »P Sieve number! or Aver- f Maxi- Bia nt Wire diameter size in inches age Mm. Jere TG Berea bee 8 OPeRs) a saute Open ing | Under | Over | ing | | | No. 100 0.1490 .0059,0. 102 0.0040 6 15 35 40 No. 50 0.297,0.0117|0.188 0.0074 6 15 35 40 No. 30 0.59 |0.02320.33 |0.0130 5 15 30 25 No 16 1.19 |0.0469,0.54 |0.0213 3 15 30 10 No. 8 2.38 |0.0937/0.84 |0.0331 3 15 30 10 Nor 4 4.76 |0.187 {1.27 |0.050 3 15 30 10 3¢ in. 9.5 |0.375 |2.33 |0.092 3 10 10 10 24 in, 19.0 (0.75 (3.42 |0.135 3 10 10 10 to doin, 20.4 {1.00 |4.12 |0.162 3 10 10 10 14 in. 38.0 {1.50 [4.50 |0.177 3 10 10 10 east 50.8 |2.00 /|4.88 |0.192 3 10 10 10 3. in. 7.0 |3.00 (6.3 |0.25 3 10 10 10 1 The requirements for sieves No. 100 to No. 4 conform to the requirements of the U. S Standard Sieve Series as given in U. S. Bureau of Standards Letter Circular No. 74. The liberal tolerances will permit the use of certain sieves which do not exactly correspond to the numbers given in table. 2. Treatment of Sample. The sample shall be dried at not over 110°C. (230°F.) to constant weight. 3. Sieves. (a) The sieves shall be of square mesh wire cloth and shall be mounted on substantial frames constructed in a manner that will prevent loss of material during sifting. (b) The size of wire and sieve openings shall be as given in Table I. 4. Procedure. (a) The sample shall be separated into a series of sizes by means of the sieves specified in Sec. 3. Sifting shall be continued until not more than 1 per cent by weight of the sample passes any sieve during 1 min. (b) Each size shall be weighed on a balance or scale which is sensitive to 1/000 of the weight of the test sample. (c) The percentage by weight of the total sample which is finer than each of the sieves shall be computed. 5. Report. (a) The percentages in sieve analysis shall be reported to the nearest whole number. (b) If more than 15 per cent of a fine aggregate is coarser than the No. 4 sieve, or more than 15 per cent of a coarse aggregate is finer than the No. 4 sieve, the sieve analysis of the portions finer and coarser than this sieve shall be reported separately. 322 CONCRETE PRACTICE APPENDIX 4 TENTATIVE METHOD OF DECANTATION TEST FOR SAND AND OTHER FINE AGGREGATES American Society for Testing Materials Serial Designation: D 136-22 T This is a Tentative Standard only, published for the purpose of eliciting criticism and suggestions. It is not a Standard of the Society and until its adoption as Standard it is subject to revision. IssuED, 1922 1. Scope. This method of test covers the determination of the total quantity of silt, loam, clay, etc., in sand and other fine aggregates. ! 2. Apparatus. The pan or vessel to be used in the determination shall be ° approximately 9 in. (230 mm.) in diameter and not less than 4 in. (102 mm.) in depth. 3. Treatment of Sample. The sample must contain sufficient moisture to prevent segregation and shall be thoroughly mixed. A representative portion of the sample sufficient to yield approximately 500 g. of dried material, shall then be dried to a constant weight at a temperature not exceeding 110°C. (230°F.). 4. Procedure. The dried material shall be placed in the pan and sufficient water added to cover the sample (about 225 ¢.c.). The contents of the pan shall be agitated vigorously for 15 sec., and then be allowed to settle for 15 sec., after which the water shall be poured off, care being taken not to pour off any sand. This operation shall be repeated until the wash water is clear. Asa precaution, the wash water shall be poured through a 200-mesh sieve and any material retained thereon returned to the washed sample. The washed sand shall be dried to a constant weight at a temperature not exceeding 110°C.. (230°F.) and weighed. 5. Calculation of Results. The results shall be calculated from the formula: Percentage of silt, clay, loam, etc. = original dry weight —weight after washing original dry weight 6. Check Determination. When check determinations are desired, the wash water shall be evaporated to dryness, the residue weighed, and the percentage calculated from the formula: x 100 weight of residue original dry weight 1 This determination of the percentage of silt, clay, loam, etc., will include all water-soluble material present, the percentage of which may be deter- mined separately if desired. Percentage of silt, loam, clay, etc. = x 100 APPEN DICES 323 APPENDIX 5 STANDARD METHOD OF TEST FOR ORGANIC IMPURITIES IN SANDS FOR CONCRETE American Society for Testing Materials Serial Designation: C 40-22 This method is issued under the fixed designation C 40; the final number indicates the year of original adoption as standard, or in the case of revision, the year of last revision. PROPOSED AS TENTATIVE, 1921; ApopTED, 1922 This method was approved May 29, 1923, as “Tentative American Standard” by the American Engineering Standards Committee. 1. Scope. The test herein specified is an approximate test for the presence of injurious organic compounds in natural sands for cement mortar or concrete. The principal value of the test is in furnishing a warning that further tests of the sand are necessary before they be used in concrete. Sands which produce a color in the sodium hydroxide solution darker than the standard color should be subjected to strength tests in mortar or con- crete before use. 2. Sample. (a) A representative test sample of sand of about 1 lb. shall be obtained by quartering or by the use of a sampler. Procedure. (b) A 12-0z. graduated glass prescription bottle shall be filled to the 414-0z. mark with the sand to be tested. (c) A 3 per cent solution of sodium hydroxide (NaOH) in water shall be added until the volume of sand and liquid after shaking gives a total value of 7 liquid oz. (d) The bottle shall be stoppered and shaken thoroughly and then allowed to stand for 24 hr. (e) A standard color solution shall be prepared by adding 2.5 c.c. of a 2 per cent solution of tannic acid in 10 per cent alcohol to 22.5 ¢.c. of a 3 per cent sodium hydroxide solution. This shall be placed in a 12-oz. prescription bottle, stoppered and allowed to stand for 24 hr., then 25 c.c. of water added. Color Value. (f) The color of the clear liquid above the sand shall be compared with the standard color solution prepared as in Paragraph (e) or with a glass of color similar to the standard solution. 3. Solutions darker in color than the standard color have a “‘color value”’ higher than 250 parts per million in terms of tannic acid. 324 CONCRETE PRACTICE APPENDIX 6 PROPORTIONS! FOR CONCRETE OF GIVEN COMPRESSIVE STRENGTH AT 28 DAYS From the 1924 Report of the Joint Committee on Standard Specifications for Concrete and Reinforced Concrete. : The table gives the proportions in which portland cement and a wide range in sizes of fine and coarse aggregates should be mixed to obtain concrete of compressive strengths ranging from 1500 to 3000 Ib. per sq. in. at 28 days. Proportions are given for concrete of four different consistencies. The purpose of the table is twofold: (1) To furnish a guide in the selection of mixtures to be used in preliminary investigations of the strength of concrete from given materials. (2) To indicate proportions which may be expected to produce concrete of a given strength under average conditions where control tests are not made. If the proportions to be used in the work are selected from the table with- out preliminary tests of the materials, and control tests are not made during the progress of the work, the mixtures in bold-face type shall be used. The use of this table as a guide in the selection of concrete mixtures is based on the following: (1) Concrete shall be plastic; (2) Aggregates shall be clean and structurally sound; (3) Aggregates shall be graded between the sizes indicated; (4) Cement shall conform to the requirements of the Standard Specifica- tions and Tests for Portland Cement (Serial Designation: C 9-21) of the American Society for Testing Materials. (Appendix 1.) The plasticity of the concrete shall be determined by the slump test carried out in accordance with the Tentative Method of Test for Consistency of Portland-Cement Concrete (Serial Designation: D 1388-25 T) of the American Society for Testing Materials. (Appendix 7.) Apply the following rules in determining the size assigned to a given aggregate: (1) Not less than 15 per cent shall be retained between the sieve which is considered the maximum size? and the next smaller sieve. (2) Not more than 15 per cent of a coarse aggregate shall be finer than the sieve considered as the minimum size.? (3) Only the sieve sizes given in the table shall be considered in applying Rules 1 and 2. 1 Based on the 28-day compressive strengths of 6- by 12-in. cylinders, made and stored in accordance with the Standard Methods of Making Compression Tests of Concrete (Serial Designation: C 39-25) of the American Society for Testing Materials. (Appendix 8.) 2 For example: a graded sand with 16 per cent retained on the No. 8 sieve would fall in the 0-No. 4 size; if 14 per cent or less were retained, the sand would fall in the 0-No. 8 size. A coarse aggregate having 16 per cent coarser than 2-in. sieve would be considered as 3-in. aggregate. 325 APPENDICES (4) Sieve analysis shall be made in accordance with the Standard Method of Test for Sieve Analysis of Aggregates for Concrete (Serial Designation: C 41-24) of the American Society for Testing Materials. (Appendix 3. ) Proportions may be interpolated for concrete strengths, aggregate sizes and consistencies not covered by the table or determined by test. PROPORTIONS FOR 1500 Ls. PER Sq. IN. CONCRETE Fine Proportions are expressed by volume as follows: Portland Cement: Aggregate: Coarse Aggregate. Thus 1:2.6:4.6 indicates 1 part by volume of portland cement, 2.6 parts by volume of fine aggregate, and 4.6 parts by volume of coarse aggregate. Size of fine aggregate cI \oo cas oOo =H fe} a So ( @) ro) Z i=) —H re fo} 4a (en) (o.@) N re) A (=>) an o g< ae Size of coarse aggregate HOMO OND HOARD THROnm HOM AtRA COMM TOYN HAAM CAAH ONIN Tod ea IS HON O15 gi od toeaa Tega O19 gi oo ht) 1D + giod id giod 419619 Onda OAD 110 B= 00 haw Oran Rand TROD 0 0 19 15 115 1 +H 018 19 +H 5 wi gg A THON tog ose od od ed 4 SHA dian vod ed 1 sO O03. 19 eg ONON RHWhm HOyr COOH DOWD MHOS HOODOO OtRD ODAWH QANHAO Osos IN THN 19.19 gyi od O19 09 siieg CN 10 wi gio Sid gid vivied ol 1919 ios SAB OS HOOR OHOn ID HO 12 O en 19 mRO AOR Dm 0 Anwor Roan OGdH OOnn Sod eg oo ogy ooo OS eg CoN ed OO g ogc 0903 vind wise st seg CN HOMH Oth OD DAMN DHOH DMON WOAH NHONM HOMHR OCHM+ OMA HOE HHA WH CGSwd staan 1519 sod Cid god DER O19 qos O18 09 00 09 «© 00 HO 6919 chat Thom OH 0g Orato IQ AWS sO O19 HOOD roared Sie) Oth oo od ed CON ONAG CNA ANd od 03 ed 4 05 03 ed 4 co Ned woo ei ioe oc > a Seas lh a as snare eewae eet eived ot ace et 4 eel aie el Aged St aet heb ots COM NINWO ANNAN WHOM BORD NAAN COON MHOSG BNOH AMA woo eg 19 Hed 19.15 si os COIs Steg 19 19 gi od O15 gi od 15 i gi od C19 giod O18 09 0 EY AOOH Ran ODOR OOS Hoa aha ODOM oONIet Oats COWS OANA NAAN AA Aad Ade Colo Bal ON CONT Coie Bal od oo ga 0303 ei Seeeate seer ea eli rear el ied ean a eee et eal tell Se i ae a dil ities DOWD ONAR CHM ANAHDH ANIM WAMN COON t1HOO nes cdr visio a HEI OG xi od OOH 09 19 Hed 19.19 i od O19 gis 1D Ht god Ord ios S18 09 0 =H +H od HHO HOOD NOD OH 09 DHaN 900.0 AO 19 NO Anas Acid AA ei ANd ANd Ando ANd AA AA eo OO NEI od ON ed 4 Ned MHhRO FAHRO AHRO AHthO AHRO FHHRO AHRO FAHRO FHHRO FAHRO FAHhO re re re re re re re re res re 5 mal OOO 6! OOF CLIO GC OHO CO Om C1O1O 0 FOC OOM CIO O10) O'O CIO ClO OO OOToLOm moloLonS PeperPryp PYPHSH HHH YPHHH YHHH HHH YHHHH BHHH HHH HPHHH HYHHH \ OC EDO \ANMO \a Ka \aen Amen co Ane O00 \NODCOOD LOD COO \Red O00 0 Leon SA co \NeDOO AMO 9 0 lS co AS ‘S \S Nace rN OLS OS 4 . As! . . . . - qi Na (=| . . . . . >» aN = : & ; A : : : et my nN q An a Aa =| q a 3° ° ° ° om =N - rv = o=t 5 ae = a “= a a) Nn saa) N A) © ~ x = =e ° ° re) re) fo) } 8 3 3 3 3 = = r. ie = is “oo Noo \oo Nxt \st \ Z Z Zi a a oN oN oN oN oN oN CONCRETE PRACTICE 326 PROPORTIONS FOR 2000 Ls. PER Sq. IN. CONCRETE Fine Proportions are expressed by volume as follows: Portland Cement Aggregate: Coarse Aggregate. Thus 1:2.6:4.6 indicates 1 part by volume of portland cement, 2.6 parts by volume of fine aggregate, and 4.6 parts by volume of coarse aggregate. Size of fine aggregate Slump, inches Size of coarse aggregate OHO ONES HOM ONAD HHO Abie? VtOQNH |MOH MOWMD CASO NAA SHAAN WAN WAN Sad voGN wWriega OIA wviega 1D Hi gi od IQR COMM HHH ANON ORS DQAWH Kas Bann Honw mane niet SIH SGM CNA HN ANi HMA MOA HN woe woes toed Seas AeA sea Seer rat onl od waist eal yal wtted ea ett mt net ont ted ted Ray ae ow HON BDQArA OOMAH CHMR OWHWO OCOMHT HHAR ACON OCNMONM DBRHAAOS CONE GOAN WHAN WGN THAN WN WA wea Noh El 19.19 sfiod INOMD COMN OHO NMHthO HOMO OH ORIC9 ANOn oman CO AHS Or 6919 O09 OOAA GAnid AA ANd ANTiO NAG one OAc Od cocoa 09 03 ed tried bo I oe oe he So Do reread rie et aoe et et wad sel welt rol ed hte miei etee ol peti so INrIBH AROMW AAW HOHO ACON Hatt HMARR HWOUN BtRO ANAS Hg WOON WHA Widdion won WHA wie WOON wwiedal 19.19 od SOOM SARS BHMS HOWH BOA DHOn OtRH SAS HOU AOC AN Oo ON ANeid Addin ANOS ANdidic ANd Addo AN OA ONES c3 ON ed 4 aoa area bs oo a sree viet ha ee wi ted et vl ld ot Reet pas dain ariel RANOQD MHAN AMNWQ MOHAR ANON WBAWMD NHRA MoNn AORN ANAS HH VAN HHA WisgGa wOaN WA wea WAN WHA wis gies ONERH NAWA NOHO Frm Bad 6WHAwod WHAMS HOWD aon 00 Oth ANed Addo Addo Addo Gai ANd Addi Addis ANd ANd ANS aoaded sea AeA reac Ase ated ot Seed wt ied et ied et eet dot wot pol pot DHQmA MAAN SHIH HOUMA HOAN AMM OHNOAR MOAM ANOKO CHA HMI WAN WHgN WidGN THAN THAN Wr gia TOAN Wan Sogn NRWO HNHH QONK ASAm KNHOS ASWA Aawa Anew SONOS BHHOS HWS Added Ando Patio HiniS rds Adi Aridio Addo AA ANd AA eee Sea Area 5 oo oe aeewae Sey pol al wel ed mt el at al vol eat el ok al ol iil APO HPO AMES AWE O NRO EO Ath ARO MRO MYR rin > ° 200 2° S828 2882 S388 S858 SESS S382 S288 BESS SESS BESS SESE WNODEOW \NODDO OC NM O CO \NMOCW WOO OCO \NMDOCO MMOH \NODOW \NMDOCW \NMOC NOOO 28 ae PN aN a 2 aS ae None.... No. 4 to 34 in.. No. 4 to lin... No. 4 to 134 in. No. 4 t0\2:ine.. $2 to Lin... 3g to l}gin.... Se to. 2: ines oe $4 to 132 in.. 34. to 2 in. ss... $4 to'3. in. Ni che 5 3 laa) A 5. a © a oa & 35° ica) o q Ei Cress es wd OSs Se iS, o) & . a Z, me ee ° — mM fe, : a g2% rom o mS a = ¢g w & op) Lass} 5 cae ta S : © 5S Se ay go Mea IS Zz A a yee. A ie ie ee = N et a ee ied Cin ee ee es Z & § 2 oo 0 O SO & Weg e $< 8 ° 2 Ro oy pas) as fe) a . a oe q © mM 6c a 5, ere 5.8 = & 8 5 oO oO Bes Bes Ay. SBE < by volume of fine aggregate, and 4.6 parts by volume of coarse aggregate. Size of fine aggregate s \oo =. oOo = re) a ro) CO 3 Z roo) + re fe) Z ro) (o.6) N fe) a ° a2 sel aS em Size of coarse aggregate } } } } - } } less Tle eee {ee TC uee—_—_ i Tr i er nr OTe eer — Tee ees NS d ; A 5 : ; : ; —_ q q . . . . Ae —_ be = e qd a qa Fy = 3 “ x F & E te E 2 . [o} fe) [e) fe) om bi, -_ St m _ Coal i © os a 2 co) qo A = i) aa) © ~ Bi a } ° ° } } ° i=} . A . : a=) E S S S S o ae ie es = . iz Z Zz a Zi on EN on on oN oN CONCRETE PRACTICE 328 CONCRETE PER Sq. IN. Proportions FOR 3000 Lp. Proportions are expressed by volume as follows: Portland Cement: Fine Aggregate: Coarse Aggregate. Thus 1:2.6:4.6 indicates 1 part by volume of portland cement, 2.6 parts by volume of fine aggregate, and 4.6 parts by volume of coarse aggregate. Size of fine aggregate | - - s fe) = o lo) eC) mn o st bs | fe} a j=) ie.) N fe} a So 28 S5 ae Size of coarse aggregate INONE:....- No. 4 to 34 in.. No; 4 toil in... No. 4 to 14 in. No. 4 to 2.1n7).. 36 to lin... 3g to 1}4 in.... 34 to 2in... $4 to-2 in... 34) toroid eaeneys APPENDICES ; o29 APPENDIX 7 TENTATIVE METHOD OF TEST FOR CONSISTENCY OF PORTLAND CEMENT CONCRETE American Society for Testing Materials Serial Designation: D 138-25 T This is a Tentative Standard only, published for the purpose of eliciting criticism and suggestions. It is not a Standard of the Society and until its adoption as Standard it is subject to revision. IssuED, 1922; Revisep 1925 1. Scope. This test covers the method to be used both in the laboratory and in the field for determining consistency of concrete.} Lop rep 3 pa ee eee Pa Go cel ee «es Elevation. " Las xe st ae ee ~ By st ny aN ly y 1 This test is not considered applicable when there is a considerable amount of coarse aggregate over 2 in. in size in the concrete. The committee is now working on a method suitable for determining the consistency of con- crete using aggregate over 2 in, in size. 330 CONCRETE PRACTICE 2. Apparatus. The test specimen shall be formed in a mold of No. 16 gage galvanized metal in the form of the lateral surface of the frustrum of a cone with the base 8 in. in diameter, the upper surface 4 in. in diameter, and the altitude 12 in. The base and the top shall be open and parallel to each other and at right angles to the axis of the cone. The mold shall be provided with foot pieces and handles as shown in Fig. 1. 3. Sample. When the test is made at the mixer, the sample shall be taken from the pile of concrete immediately after the entire batch has been dis- charged. When testing concrete that has been hauled from a central mix- ing plant, the sample shall be taken from the concrete immediately after it has been dumped on the subgrade. 4. Procedure. The mold shall be placed on a flat, non-absorbent surface, such as a smooth plank or a slab of concrete, and the operator shall hold the form firmly in place, while it is being filled, by standing on the foot pieces. The mold shall be filled to about one-fourth of its height with the concrete which shall then be puddled, using 20 to 30 strokes of a %-in. rod pointed at the lower end. The filling shall be completed in successive layers similar to the first and the top struck off so that the mold is exactly filled. The mold shall then be removed by being raised vertically, immediately after being filled. The molded concrete shall then be allowed to subside, until quiescent, and the height of the specimen measured. 5. Slump. The consistency shall be recorded in terms of inches of sub- sidence of the specimen during the test, which shall be known as the slump. Slump = 12 — inches of height after subsidence APPENDIX 8 STANDARD METHODS OF MAKING COMPRESSION TESTS OF CONCRETE American Society for Testing Materials Serial Designation: C 39-25 These methods are issued under the fixed designation C 39; the final number indicates the year of original adoption as standard or, in the case of revision, the year of last revision. PROPOSED AS TENTATIVE, 1921; ApopTED, 1925 1. Scope. These methods are intended to cover compression tests of con- crete made in a laboratory where accurate control of quantities of materials and test conditions is possible. They are designed to apply primarily to hand-mixed concrete. ‘These methods may be used with slight modifica- tion in making tests of concrete for wearing resistance, bond between con- APPENDICES dol crete and steel, impermeability, etc. The investigation of machine-mixed concrete will require certain obvious changes in the method. For methods of conducting compression tests of concrete specimens made during the progress of construction work, see the Standard Methods of Making and Storing Specimens of Concrete in the Field (Serial Designation: C 31) of the American Society for Testing Materials.1 2. Preparation of Materials. Materials shall be brought to room tem- peratures (65 to 75°F.) before beginning tests. Cement shall be stored in a dry place; preferably in covered metal cans. The cement shall be thor- oughly mixed in advance, in order that the sample may be uniform through- out the tests. It shall be sifted through a No. 16 sieve and all lumps rejected. Aggregates shall be in a room-dry condition when used in con- crete tests. In general, aggregates should be separated on the No. 4, 3<-in. and 114-in. sieves? and recombined to the average original sieve analysis for each batch. Fine aggregate should be separated into different sizes also, in cases where unusual gradings are being studied. 3. Sampling for Preliminary Tests. Representative samples? of all concrete materials shall be secured for preliminary tests prior to the pro- portioning and mixing of the concrete. Cement test samples may be made up of a small quantity from each sack used in the concrete tests. Test samples of aggregates may be taken from larger lots by quartering. 4. Cement Tests. Cement shall be subjected to test, using the methods described in the Standard Specifications and Tests for Portland Cement (Serial Designation: C 9) of the American Society for Testing Material.‘ 5. Fine Aggregate Tests. Fine aggregates (passing through a No. 4 sieve) shall be subjected, when required, to the following tests: (a) Sieve analysis test made in accordance with the Standard Method of Test for Sieve Analysis of Aggregates for Concrete (Serial Designation: C 41) of the American Society for Testing Materials.5 (b) Test for organic impurities (natural sand only) made in accordance with the Standard Method of Test for Organic Impurities in Sands for Concrete (Serial Designation: C 40) of the American Society for Testing Materials. ® 11924 Book of American Society for Testing Materials Standards and Appendix 9. 2 For specifications for sieves, see Standard Method of Test for Sieve Analysis of Aggregates for Concrete (Serial Designation: C 41) of the American Society for Testing Materials, Appendix 3. 3 For methods of sampling large lots of deposits of aggregate, see the Standard Methods of Sampling Stone, Slag, Gravel, Sand, etc., for Use as Highway Materials (Serial Designation: D 75) of the American Society for Testing Materials, 1924 Book of A. S. T. M. Standards. 4 Appendix 1. 5 Appendix 3. 6 Appendix 5. 332 CONCRETE PRACTICE (c) Test for quantity of silt, clay, or dust made in accordance with the Tentative Method of Decantation Test for Sand and Other Fine Aggre- gates (Serial Designation: D 136-22 T) of the American Society for Testing Materials. (d) Test for unit weight made in accordance with the Standard Method of Test for Unit Weight of Aggregate for Concrete (Serial Designation: C 29) of the American Society for Testing Materials.” (e) Strength test of 1:3 mortar by weight at 7 and 28 days in comparison with standard sand mortar. 6. Coarse Aggregate Tests. Coarse aggregates (retained on a No. 4 sieve) shall be subjected when required to the following tests: (a) Sieve analysis test as specified under Sec. 5 (a); (b) Test for quantity of silt, clay, or dust, as specified under See. 5 (c); (c) Test for unit weight as specified under Sec. 5 (d). 7. Mixed Aggregate Tests. The unit weight of mixed fine and coarse aggregates as used in concrete tests shall be determined in accordance with the method specified in Sec. 5 (d). 8. Proportioning. ‘The quantities of each size of aggregate to be used in each batch shall be determined on the basis of the sieve analysis and the unit weight of the mixed aggregate. The exact quantities of cement and of each size of aggregate for each batch shall be determined by weight. The quantity of water for each batch shall be accurately measured. ‘The quantities of materials may be expressed as (a) 1 volume of cement to — volumes of total aggregate mixed as used, or (b) 1 volume of cement — volumes fine aggregate, and — volumes of coarse aggregate. Notr.—It is impracticable to give a general method for proportioning concrete for experimental purposes; the details will necessarily vary widely with the purpose for which the tests are made. The following procedure is suggested for specific cases: (a) Vary the cement content by 10 per cent intervals above and below assumed quantity. (b) Vary the proportions of fine to coarse aggregate, measured sepa- rately, at intervals of 10 per cent. (c) Vary the quantity of mixing water by intervals of 10 per cent. 9. Size of Test Pieces. Compression tests of concrete shall be made on cylinders of a diameter equal to one-half the length. The standard shall be 6- X 12-in. cylinders where the coarse aggregate does not exceed 2 in. in size; for aggregates larger than 2 in., 8- X 16-in. cylinders shall be used; 2- X 4-in. cylinders may be used for mixtures without coarse aggregate. 10. Mixing Concrete. (a) Concrete shall be mixed by hand in batches of such size as to leave a small quantity of concrete after molding a single test piece. The batch shall preferably be mixed in a shallow galvanized steel pan with a 10-in. bricklayer’s trowel which has been blunted by cut- ting off about 2% in. of the point, as follows: 1 Appendix 4. 2 Appendix 2, APPENDICES 330 (b) The cement and fine aggregate shall be mixed dry until the mixture is homogeneous in color; (c) The coarse aggregate shall be added and mixed dry; (d) Sufficient water shall be added to produce concrete of the required workability; Notr.—Concrete tests should be made on plastic mixtures. It is of the utmost importance that a uniform degree of workability be secured in tests involving comparisons of different materials and methods. (e) The whole shall be mixed thoroughly until the entire mass is homo- geneous in appearance. 11. Workability. The workability or plasticity of each batch of concrete shall be measured immediately after mixing by one of the following methods: (a) Slump test made in accordance with the Tentative Method of Test for Consistency of Portland Cement Concrete (Serial Designation: D 138- 25 T) of the American Society for Testing Materials.! (b) Flow test made by placing a metal form in the shape of a frustum of a cone 634 in. in top diameter, 10 in. in bottom diameter, 5 in. deep, on the table of the flow apparatus.2. The fresh concrete shall be placed in the mold in two layers. Each layer shall be puddled and finished as described in Sec. 18. Immediately after molding, the form shall be removed by a steady upward pull; the specimen raised 14 in. and dropped fifteen times in about 6 sec. by means of a suitable cam and crank. The spread of the fresh concrete due to this treatment, as compared with the original bottom diameter of the cone, expressed as a percentage, is the ‘‘flow.”’ 12. Forms. The forms shall preferably be of metal. Each form shall be provided with a machined metal base plate, and shall be oiled with a heavy mineral oil before using. Particular care shall be taken to obtain tight forms so that the mixing water will not escape during molding. Notr.—The best type of form consists of lengths of cold-drawn steel tubing, split along one element and closed by means of a circumferential band and bolt. Satisfactory forms can be made from lengths of steel water- pipe machined on the inside, from rolled metal plates, from galvanized steel, machined iron or steel castings. Paraffined cardboard molds will give good results under expert supervision. ; 13. Molding Test Pieces. Concrete test pieces shall be molded by placing the fresh concrete in the form in layers 3 to 4 in. in thickness. Each layer shall be puddled with twenty-five strokes with a 5g-in. round steel bar of a length 9 in. greater than the length of the mold, pointed at the lower end. After the top layer has been puddled, the surplus concrete shall be cleaned off with a trowel, and the mold covered with a machined metal plate or a piece of plate glass at least 14 in. thick, which will be used later in cap- ping the test piece. 1 Appendix 7. 2 For a description and illustration of one design for a flow table, see Proceedings, American Society for Testing Materials, Vol. XX, Part II, p. 242 (1920); and Concrete, p. 274, June, 1920. 334 CONCRETE PRACTICE 14. Capping Cylinders. Two to four hours after molding, the test pieces shall be capped with a thin layer of stiff, neat cement paste, in order that the cylinders may present a smooth end for loading. The cap shall be formed by means of a machined metal plate or a piece of plate glass of suitable size, at least 14 in. thick, worked down on the fresh cement paste until it rests on the top of the cylinder form. The cement for capping shall be mixed to a stiff paste before beginning to mix the concrete; in this way the tendency of the cap to shrink will be largely eliminated. The adhesion of the concrete to the metal base plate and the glass can be largely elimi- nated by oiling the cover plate and by inserting a sheet of paraffined tissue paper. 15. Curing Test Pieces. Concrete test pieces shall be removed from the forms 20 to 48 hr. after molding, marked, weighed, and stored in damp sand, under damp cloths or in a moist chamber until the date of test. The temperature of the curing room should not fall outside the range of 60 to 75°F, 16. Age at Test. Tests shall be made at the age of 7 and 28 days; ages of 3 months and 1 year are recommended, if longer-time tests are required. 17. Sequence of Tests. Three to five test pieces should be made on different days in investigations in which accurate comparisons are desired. 18. Preparation of Tests. Compression tests shall be made immediately upon removal of the concrete test pieces from the curing room; that is, the test pieces shall be loaded in a damp condition. The length and average diameter of the test piece shall be measured in inches and hundredths; two diameters shall be measured at right angles near the mid-length. The test piece shall be weighed immediately before testing. 19. Method of Testing. In general, only the ultimate compressive strength of the cylinders need be observed. The metal bearing plates of the testing machine shall be placed in contact with the ends of the test piece; cushioning materials shall not be used. An adjustable bearing block shall be used to transmit the load to the test piece. The bearing block shall be placed on top of the test piece in vertical testing machines. The diameter of the bearing block shall be approximately the same as that of the test piece. The upper section of the bearing block shall be kept in motion as the head of the testing machine is brought to a bearing on the test piece. 20. Application of Load. The load shall be applied uniformly and with- out shock. The moving head of the testing machine should travel at the rate of about 0.05 in. per min. when the machine is running idle. 21. Record of Tests. The total load indicated by the testing machine at failure of the test piece shall be recorded and the unit compressive strength calculated in pounds per square inch, the area computed from the average diameter of the cylinder being used. The type of failure and appearance of the concrete shall be noted. 22. Weight of Concrete. The weight of the concrete in pounds per cubic foot shall be determined from the weight of the specimens and their dimensions, APPENDICES 339 23. Density and Yield. Density and yield of concrete when required shall be calculated from the unit volumes of the constituent materials and the volume of the concrete. Density is here understood to be the ratio of solids in the concrete to the total volume of the mass. Yield is the volume of concrete resulting from one volume of aggregate mixed as used. 24. Report of Tests. The report of tests shall include the following: (a) The kind and origin of concrete materials. (b) Complete data on all tests of cement and aggregates. (c) A description of methods of making and testing the concrete, where methods deviate from the proposed standards. (d) The quantities of cement, aggregates, and water in each batch. (e) The method of measuring workability or plasticity with ‘‘slump”’ or “‘flow”’ of concrete. (f) The quantity of water expressed as a ratio to volume of cement. (g) The age at test. (h) The size of test pieces. (7) The date of molding and testing each cylinder. (j) The compressive strength in pounds per square inch of each test piece and average of tests in a set. (k) A description of failure and appearance of concrete on each test piece. (l) The unit weight, density, and yield of the concrete. APPENDIX 9 STANDARD METHODS OF MAKING AND STORING SPECIMENS OF CONCRETE IN THE FIELD American Society for Testing Materials Serial Designation: C 31-21 These methods are issued under the fixed designation C 31; the final number indicates the year of original adoption as standard, or in the case of revision, the year of last revision. PROPOSED AS TENTATIVE, 1902; ApDoprED, 1921 1. Scope. The methods herein specified apply to molding and storing of test specimens of concrete sampled from concrete being used in con- struction. 2. Size and Shape of Specimen. The test specimens shall be cylindrical in form with the length twice the diameter. In general, a mold whose diameter is not less than four times the diameter of the largest size aggregate shall be used. (The sizes most commonly used are 6- X 12-in. and 8- X 16-in. cylinders.) 336 CONCRETE PRACTICE 3. Molds. (a) The molds shall be cylindrical in form, made of non- absorbent material, and shall be substantial enough to hold their form during the molding of the test specimens. They shall not vary in diameter more than 14g in. in any direction, nor shall they vary in height more than 1/¢ in. from the height required. They shall be substantially watertight, so that there will be no leakage of water from the test specimen during molding. (b) Each mold shall be provided with a base plate having a plane surface and made of non-absorbent material. This plate shall be large enough in ; | ZS" ou += x3 Square Head g =f Bolt | \3 xi Steel Pipe Top ‘View. Stock : 62'0.D. Cold- Drawn Seamless Stee! Tubing; 7g Walls. Make Narrow Slit along one Side View. Element. May also Use 6 Steel Water-Pipe, Machined Inside. Slit alongone Element, so that wher Closed will give 6" Inside Diameter. Frark diameter properly to support the form without leakage. Plate glass or planed metal is satisfactory for this purpose. A similar plate should be provided for covering the top surface of the test specimen after being molded. (c) Suggestions for suitable forms are shown in Figs. 1, 2, and 3. 4, Sampling of Concrete. (a) Concrete for the test specimens shall be taken immediately after it has been placed in the work. All the concrete for each sample shall be taken from one place. A sufficient number of samples—each large enough to make one test specimen—shall be taken at different points so that the test specimens made from them will give a fair average of the concrete placed in that portion of the structure selected for EE EE a’ APPEN DICES BBv A tests. The location from which each sample is taken shall be noted clearly for future reference. (5) In securing samples, the concrete shall be taken from the mass by a shovel or similar implement and placed in a large pail or other receptacle, for transporting to the point of molding. Care shall be taken to see that each test specimen represents the total mixture of the concrete at that place. Different samples shall not be mixed together, but each sample shall make one specimen. 5. Molding the Specimens. (a) The pails or other receptacles containing the samples of concrete shall be taken as quickly as possible to the place ‘ TE fein eg See ey eM om wee ee mmowe oe wm Aone wwe wwe mw ew ec oon - 4 Sheet Iron, } ‘3x3 “Square kolled ene Head 5X1 Steel Pipe Bolt Top View. k | Side View Fia. 2. selected for molding test specimens. To offset segregation of the concrete occurring during transportation, each sample shall be dumped into a non- absorbent water-tight receptacle and, after slight stirring, immediately placed in the mold. (b) The test specimens shall be molded by placing the concrete in the form in layers approximately 4 in. in thickness. Each layer shall be puddled with twenty-five to thirty strokes with a 5£- to 34-in. bar about 2 ft. long, tapered slightly at the lower end. After puddling the top layer, the surface concrete shall be struck off with a trowel and covered with the top plate, which will later be used in capping the test specimens. 6. Capping Specimens. ‘Two to fourhours after molding, the test speci- mens shall be capped with a thin layer of stiff, neat cement paste, in order 338 CONCRETE PRACTICE that the cylinder may present a smooth end for testing. The cap can best be formed by means of a piece of plate glass 14 in. thick, and of a diameter 2 or 3 in. larger than that of the mold. This plate is worked on the fresh cement paste until it rests on top of the form. The cement for capping should be mixed to a stiff paste some time before it is to be used in order to avoid the tendency of the cap to shrink. Adhesion of the concrete to the top and bottom plates can be avoided by oiling the plates or by inserting a sheet of paraffined tissue paper. 7. Removal of Specimens from Forms. At the end of 48 hr., the test specimens shall be removed from the molds and buried in damp sand, except Kk » : 8 : 2 8 te 4% a) Ss 8 a ~ cy & _ gee 2 Pi Pat 3 : Lightly fae % ' Soldered~ or ‘Laced with Wire a ' Staples. S Top View. T) ' Ss ’ 3 ' Hy ' A ‘ Material: ; No. 20 Gage ' Galvanized ; Steel or Waxed Board, othe £02 Side View. Fia. 3. in case the molds shown in Fig. 3 are used; in this case test specimens may be buried in damp sand without removal of the mold, thus permitting ship- ping of the test specimens in the molds. 8. Storage of Specimens. (a) The test specimens shall remain buried in damp sand until 10 days prior to the date of test. They shall then be well packed in damp sand or wet shavings and shipped to the testing laboratory, where they shall be stored either in a moist room or in damp sand until the date of test. (b) Should a 7-day test be required, the test specimens shall remain at the works as long as possible to harden, and then shall be shipped so as to arrive at the laboratory in time to make the test on the required date. APPENDICES 339 APPENDIX 10 From the 1924 Report of the Joint Committee on Standard Specifications for Concrete and Reinforced Concrete. EFFECT OF OILS AND MISCELLANEOUS LIQUIDS ON CONCRETE AND METHOD OF PROTECTIVE TREATMENT WHERE REQUIRED : es Eff es Liquid seer a is Aa Surface treatment MINERAL Ors! 30° Baumé or heavier. .| Good concrete unaffect- | None—Good concrete ; ed. Very slight sur-| well spaded, or cement face penetration. mortar finish sufficient. Fuel oils above 30° || Good concrete unaffect- | Coatings of the magne- Baumé Distillates ed. More penetra-| sium fluosilicate class, Gas and lubricating tion than for heavy oils.) glues, or varnishes re- oils? quired for storage tanks. Kerosene, gasoline, | | Good concrete unaffect- | Gasoline-proof coatings DETID Eee fa iy cilens< ed. Considerable| producing glazed sur- penetration. face or treatment with iron compounds. ANIMAL O1ts (Sotip Farts)? Lard and lard oil....... May attack concrete| Various proprietary slowly, particularly if | compounds recom - in melted condition. mended by manufac- turers of technical paints. Goose fat, beef mar- | | No definite information. | Probably similar to that row, beef and mut- Probably similar to ; for lard oil. ton tallow and tal- lard oil. HS WGN Bayete sis Gs os 8 1 Signal oil, used by railroads, is a mixture of animal fat with mineral oil. Probably has about the same effect on concrete as lard oils. 2 Some lubricating oils are mixtures of mineral and animal oils. 3 Bureau of Standards tests with concrete tanks show slight roughening of surface at end of 12 months, and considerable deposit on surface through saponification. 340 CONCRETE PRACTICE Liquid ect on untreated Surface treatment concrete ANIMAL O1Ls (Liguip Farts) Marine: Menhaden oil........ No effect on good con- | Cushman’s tests indicate crete. various coatings no bet- ter than plain concrete. Cod liver GiLe .; 42 More or less disintegra- | Various proprietary Shark liver oil..... tion depending on qual-| compounds recom- Seal and whale oil.. ity of concrete. mended by manufac- turers of technical paints. Terrestrial: ) Sheep’s foot...... | More or less disintegra- | Various proprietary Horse’s foot...... tion depending on qual-| compounds recom - ity of concrete. mended by manufac- turers of technical paints. Neat a:f0ot*=. asa. No effect on good con-| No treatment required. crete. VEGETABLE O1Ls (Souip Fats) Cocostut Gis eio7. nee Some action if stored in | Several proprietary com- closed tank. Progres-| pounds seem to have sive disintegration ifin| proved effective on contact with surfaces| floors. Sodium silicate exposed to air. or magnesium fluosili- cate treatment appar- ently sufficient for closed tanks. Palm oilt¢s 2 eee No information. No information. VEGETABLE OILS Drying: Poppyseed oil..... No information. No information. 1 Bureau of Standards noted slight deposit due to saponification at end of 12 months. 2 Bureau of Standards tests with concrete tanks show considerable softening and roughen- ing of surface at end of 12 months, APPENDICES 341 Effect on untreated ao concrete Surface treatment VEGETABLE Oris (Continued) Linseed oil!........ No effect on good con- Hosmtolpes. kt... crete. Considerable Turpentine........ penetration of turpen- tine. Semidrying: No action if stored in closed tank of good con- crete. Cottonseed oil....... Progressive disintegra- tion, if in contact with surfaces exposed to air. Rape seed oil...... PaStOrOll... 2... . Mustard oil....... Non-drying: Eh Ce Probably some action. Butter oil (2) MIscELLANEOUS LIQUIDS Cushman’s tests indicate various coatings no bet- ter than plain concrete for linseed and rosin oils. Same as for cocoanut oil. Cushman’s tests show proprietary coatings of varnish type effective. Tanning liquors........ siderable effect. Other tanning extracts have no action. Attacks untreated con- crete tanks. Snlnte uguor.: i. +... .. Acetic acid attacks con- crete. Cider vinegar. .../..... Acid liquors show con-| Bituminous acid-proof paints effective for tanks holding acid tan- ning solutions. Good concrete with or with- out mortar finish suffi- cient for other tanning liquors. Cushman’s tests indicate bituminous acid-proof paints effective. Par- affin coating fair. Cushman’s tests indicate bituminous acid-proof paints effective. Par- affin coatings applied hot also useful for tanks. 1 Bureau of Standards noted at end of 12 months considerable deposit on surfaces of concrete tanks containing both boiled and raw linseed oil, due to saponification, but concrete showed no deterioration. 342 CONCRETE PRACTICE Tawaid Effect on untreated Surface treatment concrete ‘MisceLLANEous Liquips (Continued) Sauerkraut brine....... No action on good con-| Cushman’s tests show crete. special treatments no better than untreated concrete. W hey.i tien es eres More or less action de-| Cushman’s tests show pending on quality of| proprietary coating of concrete. varnish type effective. Sodium silicate treat- ment used on storage tanks. Buttermilk. oan. 1.7 eae No action on good con-| Untreated tanks used crete. successfully to store buttermilk. Molasses..............]| No action in closed con- | Good concrete well spad- crete. ed or finished with cement mortar suffi- cient. Annapolis mix- ture sometimes used. Sulfuric acid solutions. .| Progressive disintegra-| Bituminous acid-proof tion, particularly where] paints or mastic coat- concrete is subject to| ing effective. abrasion. APPENDIX 11 STANDARD SPECIFICATIONS FOR CONCRETE BUILDING BLOCK AND CONCRETE BUILDING TILE American Concrete Institute Submitted by Committee P-1, on Standard Building Units Serial Designation P—1A—25 1. GENERAL 1. The purpose of these specifications is to define the requirements for concrete building block and concrete building tile to be used in construction. 2. The word ‘‘concrete”’ shall be understood to mean portland cement concrete. I APPENDICES 343 3. Strength Requirements. According to the strength in compression 28 days after being manufactured or when shipped, concrete block and concrete tile shall be classified as heavy-load-bearing, load-bearing, and non-load-bearing on the basis of the following requirements: Compressive strength, pounds per square inch of gross cross-sectional Name of classification area as laid in the wall Minimum for in- dividual unit Average of 3 or more units Heavy-load-bearing block or tile.......... 1200 1000 Medium-load-bearing block or tile........ 700 600 Non-load-bearing block or tile........... 7 250 | 200 4. The gross cross-sectional area of a one-piece concrete block or tile shall be considered as the product of the length times the width of the unit as laid in the wall. No allowance shall be made for air spaces in hollow units. The gross cross-sectional area of each unit of a two-piece block or tile shall be considered the product of the length of the unit times one-half the thick-' ness of the wall for which the two-piece block or tile is intended. 5. The compressive strength of the concrete in units of all classifications except “‘non-load-bearing block” shall be at least 1000 lb. per sq. in., when calculated on the minimum cross-sectional area in bearing. 6. Absorption Requirements. Concrete building block and tile to be exposed to soil or weather in the finished work (without stucco, plaster, or other suitable protective covering) shall meet the requirements of the absorp- tion test. 7. All concrete building block and tile not covered by Paragraph 6 need not meet an absorption requirement. 8. Concrete block and tile shall not absorb more than 10 per cent of the dry weight of the unit, when tested as hereinafter specified, except when it is made of concrete weighing less than 140 lb. per cu. ft. For block or tile made with concrete weighing less than 140 lb. per cu. ft., the absorption in per cent by weight shall not be more than 10 multiplied by 140 and divided by the unit weight in pounds per cubic foot of the concrete under consideration. 9. Sampling.—Specimens for tests shall be representative of the com- mercial product of the plant. 10. Not less than three and preferably five specimens shall be required for each test. 11. The specimens used in the absorption test may be used for the strength test. 2. METHODS OF TESTING 12. Absorption Test.—The specimens shall be immersed in clean water at approximately 70°F. for a period of 24 hr. They shall then be removed, the surface water wiped off, and the specimens weighed. Specimens shall 344 CONCRETE PRACTICE be dried to a constant weight at a temperature of from 212 to 250°F. and reweighed. Absorption is the difference in weight divided by the weight of the dry specimens and multiplied by 100. 13. Weight of Concrete.—The weight per cubic foot of the concrete in a block or tile is the weight of the unit in pounds divided by its volume in cubic feet. To obtain the volume of the unit, fill a vessel with enough water to immerse the specimen. The greatest accuracy will be obtained with the smallest vessel in which the specimen can be immersed with its length vertical. Mark the level of the water, then immerse the saturated specimen and weigh the vessel. Draw the water down to its original level, and weigh the vessel again. The difference between the two weights divided by 62.5 equals the volume of the specimen in cubic feet. 14. Strength Test.—Specimens for the strength test shall be dried to constant weight at a temperature of from 212 to 250°F. 15. The specimens to be tested shall be carefully measured for overall dimensions of length, width, and height. 16. Bearing surfaces shall be made plane by capping with plaster of paris or a mixture of portland cement and plaster, which shall be allowed to harden thoroughly before the test. 17. Specimens shall be accurately centered in the testing machine. | 18. The load shall be applied through a spherical bearing block placed on top of the specimen. 19. When testing other than rectangular block or tile, care must be taken to see that the load is applied through the center of gravity of the specimen. 20. Metal plates of sufficient thickness to prevent appreciable bending shall be placed between the spherical bearing block and the specimen. 21. The specimen shall be loaded to failure. 22. The compressive strength in pounds per square inch of gross cross- sectional area is the total applied load in pounds divided by the gross cross- sectional area in square inches. APPENDIX 12 STANDARD SPECIFICATION FOR CONCRETE BRICK Submitted by Committee P-1, on Standard Building Units American Concrete Institute (Serial Designation P-1B-25) 1. GENERAL 1. The purpose of these specifications is to define the requirements for concrete brick to be used in construction. APPENDICES 345 2. The word “concrete” shall be understood to mean portland cement concrete. 3. The average compressive strength of concrete brick 28 days after being manufactured or when shipped shall not be less than 1500 lb. per sq. in. of gross cross-sectional area as laid in the wall, and the compressive strength of any individual brick shall be not less than 1000 lb. per sq. in. of gross cross-sectional area as laid in the wall. 4. The gross cross-sectional area of a brick shall be considered as the product of the length times the width of the unit as laid in the wall. 5. Concrete brick shall not absorb more than 12 per cent of the dry weight of the brick when tested as hereinafter specified, except when they are made of concrete weighing less than 125 lb. per cu. ft. For brick made of concrete weighing less than 125 lb. per cu. ft., the average absorption in per cent by weight shall not be more than 12 multiplied by 125 and divided by the unit weight in pounds per cubic foot of the concrete under consideration. 6. Specimens for tests shall be representative of the commercial product of the plant. 7. Five specimens shall be required for each test. 8. The specimens used in the absorption test may be used for the strength test. 2. METHODS OF TESTING 9. Absorption Test.—The specimens shall be immersed in clean water at approximately 70°F. for a period of 24 hr. They shall then be removed, the surface water wiped off, and the specimens weighed. Specimens shall be dried to a constant weight at a temperature of from 212 to 250°F., and reweighed. Absorption is the difference in weight divided by the weight of the dry specimens and multiplied by 100. 10. Strength Test.—Specimens for the strength test shall be dried to constant weight at a temperature of from 212 to 250°F. 11. The specimens to be tested shall be carefully measured for overall dimensions of length, width, and thickness. 12. Bearing surfaces shall be made plane by capping with plaster of Paris or a mixture of portland cement and plaster, which shall be allowed to harden thoroughly before the test. 13. Specimens shall be accurately centered in the testing machine. 14. The load shall be applied through a spherical bearing block placed on top of the specimen. 15. Metal plates of sufficient thickness to prevent appreciable bending shall be placed between the spherical bearing block and the specimen. 16. The specimen shall be loaded to failure. 17. The compressive strength in pounds per square inch of gross cross- sectional area is the total applied load in pounds divided by gross cross- sectional area in square inches, 346 CONCRETE PRACTICE APPENDIX 13 SPECIFICATIONS FOR PORTLAND CEMENT CONCRETE PAVEMENTS American Concrete Institute ONE-COURSE PORTLAND CEMENT CONCRETE PAVEMENTS FOR HIGHWAYS I. GENERAL 1. It is the intent of these specifications to cover the requirements for the materials and construction of Portland Cement Concrete Highway Pavement wherein the concrete is of uniform proportions from top to bot- tom of slab. II. MATERIALS (A) Cement 2. Cement shall be a standard portland cement which, at the time it is incorporated in the pavement mixture, shall conform to the Standard Specifications and Tests for Portland Cement (Serial Designation: C 9-21) of the American Society for Testing Materials, and subsequent revisions thereof, (B) Aggregates 3. Prior to placing any orders for aggregates, the contractor shall advise the engineer of the proposed source or sources of supply of aggregates. The engineer may require the contractor to submit 50-lb. samples of all aggregates proposed for use. If the engineer finds such samples fulfill the requirements of these specifications for aggregates, similar material shall be considered as acceptable. Acceptance of samples shall not be construed as a guarantee of acceptance of all materials from the same source, and it shall be understood that any aggregates which do not meet with the requirements of these specifications will be rejected. Upon receiving noti- fication of the proposed source or sources of aggregate supply, the engineer may elect to investigate and test the aggregate supply at the source; in which case he shall notify the contractor as to acceptability, or non-accept- ability of the proposed aggregates. ‘The engineer shall notify the con- tractor, after agreement upon a source or sources of aggregate supply, whether routine tests of aggregates during construction will be made at the source of supply or at the point of receipt. 4. (a) Fine Aggregate.—Fine aggregate shall consist of natural sand, stone screenings, slag sand, tailings, chatts, or other inert materials with APPENDICES 047 similar characteristics, or a combination thereof, having clean, hard, strong, durable, uncoated grains. When incorporated in the pavement mixture, fine aggregate shall be free from frost, frozen lumps, injurious amounts of dust, mica, soft or flaky particles, shale, alkali, organic matter, loam, or other deleterious substances. Ninety-five per cent of the fine aggregate, when dry, shall pass a one-fourth (14)-inch sieve; not more than 25 per cent shall pass a 50-mesh sieve, and not more than 5 per cent by weight shall pass a 100-mesh sieve. In no case shall fine aggregate be accepted con- taining more than 3 per cent, by dry weight, nor more than 5 per cent by dry volume, nor more than 7 per cent by wet volume, of clay, loam, or silt. If any sample of fine aggregate shows more than 7 per cent of clay, loam, or silt, in 1 hr.’s settlement after shaking in an excess of water, the material represented by the sample will be rejected. Fine aggregate shall be of such a quality that mortar composed of portland cement and the fine aggregate, when made into 2- X 4-in. cylinders, in the same proportions as will be used in the concrete mixture for the pavement, shall show com- pressive strength at 7 and 28 days equal to, or greater than, the compressive strength of cylinders composed of mortar of the same proportions of port- land cement and standard Ottawa sand. For proportioning test cylinders, portland cement and fine aggregate and standard Ottawa sand shall be measured by weight and the same portland cement shall be used with the Ottawa sand as with the fine aggregate to be tested. 5. (b) Coarse Aggregate.-—Coarse aggregate shall consist of one of the following materials, or a combination thereof; crushed rock, pebbles (gravel), air-cooled blast-furnace slag, chatts, or tailings. The particles of coarse aggregate shall be of clean, hard, tough, durable material, free from vege- table or other deleterious substances, and shall contain no soft, flat, or elongated pieces. Coarse aggregate, except air-cooled blast-furnace slag, shall show not more than 6 per cent loss in the wear test. (Nore: In many cases, it will be necessary for the engineer to specify the sizes, grading, and quality of coarse aggregate in accordance with local conditions. In every case, the engineer should provide specifications which will require the use of the best coarse aggregate which is economically available. The following specifications covering size and grading of coarse aggregate will be found applicable in most sections of the country, and are intended for use with the 1:2:3%, 1:2:3, or 1:114:3, mixture.) 6. The size of the coarse aggregate shall be such as to pass a 3-in. round opening. Coarse aggregate shall be uniformly graded within the limits shown in the following table, and any material which does not come within the limits specified shall be rejected. Passing 3-in. round opening, 100 per cent. Passing 2-in. round opening, not less than 82 per cent nor more than 95 per cent. Passing 4-in. round opening, not less than 15 per cent nor more than 25 per cent. Passing 14-in. sieve, not more than 5 per cent. 348 CONCRETE PRACTICE 7. Crushed rock shall consist of particles of rock produced by quarrying and crushing ledge rock, field boulders, or pebbles, from which, after crush- ing, all dust and pieces below one-quarter (14)-inch size have been screened out. Crushed rock shall conform in quality to the specifications under ‘“‘Coarse Aggregate.” 8. Pebbles (gravel) shall consist of loose material containing only particles retained upon a 14-in. sieve, resulting from the natural crushing and ero- sion of rocks. Pebbles must have wearing qualities at least equal to crushed stone. Pebbles shall conform in quality to the specifications under ‘‘ Coarse Aggregate.” 9. Air-cooled blast-furnace slag—The broken slag shall consist of roughly cubical fragments of air-cooled blast-furnace slag, reasonably uniform in density and quality and reasonably free from metallic iron, containing no dirt or other objectionable matter. The slag shall weigh not less than seventy (70) pound per cu. ft. 10. Chatts, or tailings, are terms locally applied to by-products, or waste products, of certain mining and industrial operations. When used as coarse aggregate for concrete pavements, such materials shall substantially conform to the specifications under ‘‘Coarse Aggregate.” 11. (c) Mixed Aggregate-—Mixed aggregate shall consist of a combina- tion of fine and coarse aggregates. That portion of mixed aggregate passing a one-quarter (14)-inch sieve shall conform to the requirements for fine aggregate; and that portion of mixed aggregate retained on a one-quarter (14)-inch sieve shall conform to the requirements for coarse aggregate. (C) Water 12. Water shall be clean, free from oil, acid, alkali, or vegetable matter. (D) Reinforcement 13. Reinforcement shall consist of steel fabric, or of steel bars, or a com- bination of both, and shall have an effective weight exclusive of dowel bars at joints and of circumferential bars of at least ...... lb. per 100 sq. ft. 14. (a) Steel Fabric.—Steel fabric shall be manufactured from cold- drawn wire, and shall comply with tentative standards of the American Society for Testing Materials, Serial Designation A 82-21 T. 15. The spacing of primary members shall be not more than ...... in., and of secondary members not more than ...... in. 16. (b) Steel Bar Reinforcement.—This style of reinforcement shall consist of steel bars of the size, shape, and spacing shown on the plans, and shall be properly formed into mats. All intersections of longitudinal and transverse bars along the exterior edges of the mat and every other intersection of the longitudinal and transverse bars in the interior of the mat shall be securely wired or clipped together to resist displacement during handling and concreting operations. ‘The materials shall have an effective weight of not less than ...... lb. per 100 sq. ft., exclusive of laps, ties, clamps, chairs, and such portions of the bars as are not in the plane of the mat for their full lengths. APPENDICES 349 17. Steel bars shall comply with the standard requirements for concrete reinforcement bars, structural and intermediate grades, of the American Society for Testing Materials, Serial Designation A 15-14. All bar rein- forcement, when placed in the pavement, shall be free from excess rust, scale or other substance which prevents the bonding of the concrete to the reinforcement. When in storage on the work, bars shall be protected from corrosion by placing them on a dry platform under a weatherproof cover. (E) Joint Filler 18. Joint filler shall consist of prepared strips of fiber matrix and bitu- men, containing not more than 25 per cent of inert material, having thickness of ...... in., and width equal to ...... in. greater than the _ thickness of the pavement at any point. The bitumen used in manufacture of the joint filler may be either tar or asphalt of a grade that will not become soft enough to flow in hot weather, nor brittle in cold weather. The prepared strips shall be cut to conform to the cross-section of the pave- ment and in lengths equal to the width of the pavement, except that strips equal in length to half the width of the pavement may be used when laced or clipped together at the center in a workmanlike and effective manner. (F) Shoulders 19. (Any special materials for the construction of shoulders should be here described as desired by the engineer.) lil. SUBGRADE 20. Subgrade will be considered as that portion of the highway upon which the pavement is to be placed. (A) Fine Grading 21. Fine grading will include the finished excavation and embankment which may be necessary to bring the subgrade to the required elevation, alignment, and cross-section. All suitable materials removed from the excavation in fine grading shall be used as far as practicable in the forma- tion of the embankment, as may be required. Such material not used in embankment may be deposited on the shoulders as directed by the engi- neer. When the amount of the embankment exceeds the amount -of the material available from excavation, suitable material shall be obtained by the contractor from borrow pits located beyond the limits of the shoulders or embankment slopes. Such borrow pits shall be left in neat condition, such as will drain completely. Ditch sections and back slopes of cuts must conform to the plans, and be left with neat and uniform appearance. (B) Preparation and Maintenance 22. The subgrade shall be constructed to have, as nearly as practicable, a uniform density throughout its entire width. Wherever the subgrade 350 CONCRETE PRACTICE extends beyond the lateral limits of an old roadway, or wherever an old gravel, macadam, or other hard, compared crust comes within 6 in. of the elevation of the finished subgrade, such old roadway or crust shall be ploughed, loosened, or scarified to a depth of at least 6 in., and the loosened material redistributed across the full width of the subgrade, adding suit- able material, when necessary, so that when compacted to the required elevation, alignment, and cross-section, the subgrade will approach, as nearly as possible, a condition of uniform density. Compression of the subgrade material shall be accomplished with a self-propelled roller weigh- ing not less than 3 tons. Hand-tamping portions of the subgrade may be directed by the engineer when necessary, ‘There shall not be left on the subgrade or shoulders, berms or ridges of earth or other material that will interfere with the immediate discharge of water from the subgrade to the side ditches, and the subgrade shall be maintained free from ruts so that it will, at all times, drain properly. 23. All depressions developing under traffic on the subgrade, or in con- nection with rolling, shall be filled with suitable material. Rolling shall be continued until the subgrade is uniformly compacted, properly shaped, and true to grade and alignment. It is not intended that the rolling shall be continued beyond this point, as the purpose of rolling is not to produce a subgrade that cannot be further compacted, but to produce a uniformly compacted subgrade. All hauling shall be distributed over the width of the subgrade so far as practicable, so as to leave it in a uniformly compacted condition. 24. After being prepared in the above manner, the subgrade shall be so maintained until the concrete pavement has been placed thereon. (C) Checking and Acceptance 25. Immediately prior to placing concrete pavement on the subgrade, it shall be checked by means of an approved scratch template, resting on the side forms, having the scratch points placed not less than 8 in. apart, and to the exact elevation and cross-section for the subgrade surface. The scratch template shall be drawn along the forms so that the plane of the points will be at a right angle to the grade line, and the long axis of the template at a right angle to the center line of the pavement. All high places indicated by the scratch points shall be removed to trude grade, and any low places back filled with suitable material, and rolled or hand-tamped until smooth and firm. The subgrade shall be checked and completed in accordance with these requirements for a distance of not less than 100 ft. in advance of the concrete. If hauling over the subgrade after it has been finished and checked as above specified results in ruts or other objection- able irregularities, the contractor shall reroll or hand-tamp the subgrade and place it in smooth and satisfactory condition before the pavement is deposited upon it. If the condition of the subgrade is such that it can- not be placed in satisfactory condition to receive the pavement by the above methods, placing pavement may be stopped by the engineer, unless the contractor can provide and haul over suitable trackways or use other satisfactory means for the protection and maintenance of the subgrade. APPENDICES dol (D) Special Treatment 26. (Special treatment may be specified for certain subgrades such as sand, gumbo, adobe, and other materials, which cannot be satisfactorily prepared for pavement by the methods specified in the foregoing paragraphs.) IV. FORMS (A) Materials 27. Wooden forms shall be dressed to 3-in. thickness, and equal in depth to the thickness of the pavement at the sides. Forms shall rest upon stakes driven into the ground within 1 ft. of each end of each separate piece, and at intervals not greater than 5 ft. elsewhere. Forms shall be held by stakes . driven into the ground along the outside edge at intervals of not more than 6 ft., two stakes being placed at each joint. The forms shall be firmly nailed to the side stakes, and firmly braced at any point where necessary to resist the pressure of the concrete or the impact of the tamper. Forms shall be capped along the inside upper edge with 2-in. angle irons. 28. Metal forms shall be of shaped steel sections not less than 10 ft. in length, for tangents and for curves having radii of 150 ft. and over. For curves of less radii, sections 5 ft. long may be used. Forms must have a depth equal to the side thickness of the pavement. Forms shall be made of steel plate of approved section. At least three bracing pins or stakes shall be used to each 10 ft. of form, and the bracing and support must be ample to resist the pressure of the concrete and the impact of the tamper without springing. (B) Setting 29. Forms shall be set to exact grade and alignment at least 500 ft. in advance of the point of depositing concrete. Before setting, the sections must be thoroughly cleaned. After setting, they shall be thoroughly oiled before concrete is placed against them. Forms in place will be subject to check and correlation of line or grade at any time. V. PAVEMENT SECTION 30. Width, thickness, and crown of concrete pavement shall be as shown on the plans for the improvement. VI. JOINTS 31. The joints to be formed shall be transverse or longitudinal. They shall be tested during and after finishing with a 10-ft. straightedge, and any irregularities in the surface shall be immediately corrected. Expansion joints shall be formed between the pavement under construction, and all other rigid types of pavement or structures to whichit may be adjacent. All joints shall be edged to a radius of } in. Joints shall be made as follows: (A) Transverse Expansion Joints 32. Transverse expansion joints shall be .......... in. wide, spaced eeranhir ss ft. apart. A bulkhead cut to the exact cross-section of the 302 CONCRETE PRACTICE pavement shall be securely staked in place at right angles to the center line and surface of the pavement. The premolded joint filler shall be placed against the bulkhead and held in position by pins on which there is an outstanding lug. Concrete shall be deposited on both sides of the bulkhead before it is removed. After the concrete has been struck off, the bulkhead shall be removed by lifting it slowly from one end and replacing it with concrete as it is lifted, so that the joint filler will be left in the correct position. 33. When expansion joints are made at the end of the day’s work, they shall be formed by finishing the concrete to the bulkhead, placed as before specified. When work is resumed, the joint filler shall be placed against the hardened concrete, and held in position by pins until fresh concrete is placed against it. 34. In pavements with integral curb, the joint shall be continuous in a straight line through pavement and curb. 35. Joints shall be opened on the edges for their entire depth, upon removal of the forms. 36. Before the pavement is ges to traffic the joint filler shall be trimmed off to a uniform height of }4 in. above the surface of the pavement. (B) Longitudinal Expansion Joints 37. Longitudinal expansion joints shall be formed by placing the filler against the form, bulkhead, curb, or adjacent structure and placing the concrete against it. The filler shall extend the full depth of the pavement, and be flush with the pavement surface. (C) Transverse Construction Joints 38. Transverse construction joints shall be formed whenever it is necessary to stop concreting for 30 min. or longer, except at expansion joints, by stak- ing in place a bulkhead, as specified for transverse expansion joints, and finishing the concrete to the bulkhead. An edging tool shall be used along the bulkhead to make the construction joint a regular and well-defined line. When the plans require steel dowels across transverse joints in this bulkhead there shall be holes spaced 3 ft., center to center, 3 in. below the surface of the finished pavement, through which 34-in. plain round steel rods 4 ft. long shall be inserted with 2 ft. projecting. At least one-half length of each bar shall be encased in heavy paper or coated with paint or oil in such a manner as to prevent a bond between the steel and the concrete. 39. When work is resumed, the plank shall be removed, care cane taken not to disturb the rods or the concrete. The fresh concrete shall be placed: directly against the face of the concrete previously laid and carefully worked around the rods. 40. If concreting must be stopped within 10 ft. of a previously made trans- verse joint, the concrete shall be removed to this joint. (D) Longitudinal Construction Joints 41. Longitudinal construction joints shall be formed where required, and must be straight and vertical. When so indicated on the plans, steel dowles shall be used as provided in the preceding section. APPENDICES 300 VII. WATER SUPPLY (A) Equipment 42. Where necessary for the supply of water for all operations described in these specifications, duplicate pumps, connected to an adequate pipe line along the improvement, shall be provided by the contractor. The pipe line must be fitted with drains at the low points, and air relief valves at the high points, and with convenient outlets for all paving operations. Where the concrete mixer operates on the subgrade, the pipe line shall have a minimum diameter of 2in. For supplying a mixer using more than 4 sacks of cement per batch, 60 per cent of the pipe line shall have a minimum diameter of 3 in., and the remaining 40 per cent shall have a minimum diameter of 2in. The large diameter pipe shall lead from the pump. (B) Priority to Water Supply 43. The concrete pavement in place, for 10 days after laying, and the subgrade preparation, shall have prior rights to the water supply. If it should develop there is not sufficient water for all purposes, the concrete mixer shall be shut down until the water needs of the curing and subgrading operations have been cared for. VIII. PROPORTIONING AND MIXING CONCRETE (A) Proportioning 44, (a) Measuring Materials.—The method of measuring materials for the concrete, including water, shall be such as to insure the required proportions of each of the materials as directed by these specifications. One sack of portland cement (94 lb. net) shall be considered 1 cu. ft. 45. (b) Proportions.—The concrete shall be proportioned 1 sack of port- land cement, not more than ............ cu. ft. of fine aggregate, and not MOPS AGM Pe cu. ft. of coarse aggregate. A cu. yd. of concrete in place, measured between neat lines, must contain ............ barrels of portland cement. ‘The engineer shall compare the calculated amount of cement required by these specifications with the amounts actually used in @ach. section Of concrete ............ ft. long, or between successive transverse joints. If the amount of cement actually used in the pavement varies from the specified amount by more than 3 per cent for any section, the engineer may require the proportions of the concrete to be adjusted so as to use the specified amount of cement. If it is found that the amount of cement used in any section is 9214 per cent, or less, of the specified quantity, the contractor shall be required to remove such section or sections, and replace them with concrete made in accordance with these specifications. Such removal and replacement shall be done at the expense of the contractor. (B) Mixing 46. (a) Operation of Mixer.—The concrete shall be mixed in a batch mixer, with the “boom and bucket” type of delivery. The capacity of the drum 354 CONCRETE PRACTICE shall be such that only whole bags of cement are used in each batch. Mix- ing shall continue for at least 1 min. after all materials, including water, are placed in the drum, and before any part of the batch is discharged. The drum shall be revolved not less than 14 nor more than 18 revolutions per minute. The drum shali be completely emptied before receiving materials for the succeeding batch. ‘The volume of the mixed material in each batch shall not exceed the mixer manufacturer’s rated capacity of the drum. 47. The mixer shall be provided with a water measuring tank into which mixing water shall be discharged, having a visible gage so that the amount of water for each batch may be separately and accurately measured. The mixer shall be provided with an approved batch-timing device, which will automatically lock the batch-discharging device during the full mixing time and release it at the end of the mixing period. The timer device shall have a bell which will automatically ring at the end of the mixing period. This device shall be subject to inspection and adjustment by the engineer at any time. 48. (b) Retempering.—Mortar or concrete which has partially set shall not be retempered by being mixed with additional materials or water. 49. (c) Central Mixing Plants.—The use of central mixing plants and the transportation of mixed concrete is permitted under these specifications, provided there is no segregation of the mixed concrete, when it is delivered at the point where it is to be deposited in the pavement. ‘The period between mixing and placing in the pavement shall not exceed 40 min., and this period may be reduced at the direction of the engineer. The concrete must be of workable consistency when placed on the subgrade. ~ Be 50. (d) Consistency.—The concrete mixture shall contain no more water than is necessary to produce a workable mass which can be brought to a satisfactory finish in the pavement. The amount of water used shall not exceed 614 gal. per sack of cement, when the aggregates are dry. IX. PLACING CONCRETE AND REINFORCEMENT (A) Inspection of Subgrade 51. (a) Rechecking Subgrade.—Immediately before placing concrete, or any type of reinforcement, the subgrade shall be rechecked by means of a scratch template as provided in paragraph 25 of these specifications, and any inequalities corrected as therein provided. 52. (b) Condition of Subgrade.—Concrete shall be placed only on a moist subgrade, but there shall be no pools of standing water. If the subgrade is dry, it shall be sprinkled with as much water as it will absorb readily, The engineer may direct that the subgrade be sprinkled or thoroughly wet down from 12 to 36 hr. in advance of placing concrete, where such procedure may be deemed necessary. (B) Placing Reinforcement 53. Steel fabric reinforcement of the size and weight shown on the plans shall be placed 2 in. below and parallel to the finished surface of the pavement - ~~) ae APPENDICES 355 unless otherwise indicated. Fabric shall extend to within 2 in. of sides and ends of slabs. All laps of fabric sections shall be not less than three- fourths of the spacing of members in the direction lapped. Steel bar reinforcement shall be placed 3 in. below the finished surface of the pave- ment unless otherwise indicated on the plans. Transverse bars shall extend to within 2 in. of the margins of the pavement. Bar reinforcement shall be placed and securely supported in correct position before any concrete is laid. All intersections of longitudinal and transverse bars shall be securely wired or clipped together to resist displacement during concreting operations. (C) Placing Concrete 54. The mixed concrete shall be deposited rapidly on the subgrade to the required depth and for the entire width of the pavement section, in successive batches and in a continuous operation without the use of intermediate forms or bulkheads between joints. While being placed, the concrete shall be vigorously sliced and spaded with suitable tools to prevent formation of voids or honeycomb pockets. ‘The concrete shall be especially well spaded and tamped against the forms. When the concrete is placed in two horizontal layers to permit use of steel reinforcement, the first layer shall be roughly struck off with a template or screed, riding on the side forms, at the correct elevation to permit placing the reinforcement in specified position. The concrete above the reinforcement shall be placed within 15 min. after the first layer has been placed. Any dust, dirt, or foreign matter which collects on the first layer shall be carefully removed before the upper layer is placed. 55. Whenever the placing of concrete is to be suspended for more than 30 min., a transverse joint shall be formed, at the point directed by the engineer to close the section. Any concrete in excess of that needed to complete a section, when work is stopped for more than 30 min., shall not be used in the pavement. (D) Finishing 56. (a) General.—Experienced and skilful workmen must be employed at all times for preparing the surface of the pavement. The concrete shall be brought to the specified contour by means of a heavy screed or template, fitted with handles, weighing not less than 15 lb. per lin. ft. This screed or template may be of steel, or of wood shod with steel. It shall be shaped to the cross-section of the pavement, and have sufficient strength to retain its shape under all working conditions. The template or screed shall rest on the side forms and shall be drawn ahead with a sawing motion. At transverse joints, the template shall be drawn not closer than 3 ft. toward the joint, and shall then be lifted and set down at the joint and drawn backwards away therefrom. Surplus concrete shall then be taken up with shovels and thrown ahead of the joint. 57. (b) Belting.—The concrete shall be finished by using a belt of wood, canvas, or rubber, not less than 6 nor more than 12 in. wide, and at least 2 ft. longer than the width of the pavement. The belt shall be applied with a combined crosswise and longitudinal motion. For the first applica- 356 CONCRETE PRACTICE tion, vigorous strokes at least 12 in. long shall be used, and the longitudinal movement along the pavement shall be very slight. The second applica- tion of the belt shall be immediately after the water sheen disappears, and the stroke of the belt shall be not more than 4 in. and the longitudinal movement shall be greater than for the first belting. 58. (c) Machine Finishing.—When a finishing machine is used, it shall be so designed and operated as to strike off and consolidate the concrete, eliminating ridges and producing a true and even surface. The operation of the machine shall be so controlled as to keep the coarse aggregate near the finished surface of the pavement. Repeated operation of the machine over a given area is to be avoided. 59. A hand-tamping template and belt must be kept for use in case the tamping machine breaks down. 60. (d) Longitudinal Floating.—Immediately after the screeding specified under IX (D) 56 (a) has been completed, the surface should be inspected for high or low spots and any needed corrections made by adding or remoy- ing concrete. Rough spots should be gone over with a long-handled float and worked to proper contour and grade. The entire surface shall then be floated longitudinally, with a float board not less than 16 ft. long and 8 in. wide. This float board shall have convenient plow handles at each end. It shall be operated by two men, one at each end, each man standing on a bridge spanning the pavement. The lower surface of the float board shall be placed upon the surface of the concrete with the long dimension parallel to the center line of the pavement. The float shall then be drawn back and forth in slow strokes about 2 ft. long, and advancing slowly from one side of the pavement to the other. The purpose of this operation is to produce a uniform, even surface on the concrete, free from transverse waves. The two bridges on which the workmen stand should be placed about 18 ft. apart when the length of the float is 16 ft. When the entire width of the pavement has been floated in this manner from one position of the bridges, they shall be moved ahead about 12 ft. so that the next section to be floated shall overlap the one previously so floated from 3 to 4 ft. After this floating has been completed,-and all transverse waves eliminated, the surface shall be finished by the belting process specified in Paragraph 57. 61. (e) Finishing at Joints and Tooling.—The contractor shall provid a suitable split float or split roller, having a slot to fit over expansion joints. This device shall be so arranged as to float the surface for a width of at least 3 ft. on each side of the joint simultaneously. This device shall be used in such manner as to produce a true surface across the joint. Edges of the pavement, at joints and side, shall be tooled for a width of 2 in., the corners rounded to a radius of 14-in. 62. (f) Trueness of Surface.—The finished surface of the pavement must conform to the grade, alignment, and contour shown on the plans. Just prior to the final finishing operation, the surface shall be tested with a light straightedge, 10 ft. in length, laid parallel to the center line of the pavement. Any deviation shall be immediately corrected. APPENDICES , oot 63. The contractor shall be held responsible for the trueness of surface of the pavement, and shall be required to make good any deviation from the alignment, grade, and contour shown on the plans. X. CURING AND PROTECTION (A) Burlap Cover 64. The contractor shall provide a sufficient amount of burlap or canvas for every mixer on the job, to cover all of the pavement laid in any one day’s maximum run. Burlap or canvas cover shall be made up in sheets 12 ft. wide, and 4 ft. longer than the width of the pavement. Burlap or canvas cover shall be placed on the concrete immediately after the final belting, and shall then be sprayed with water in such a manner that the surface of the pavement will not be damaged. Burlap or canvas cover shall be kept continuously moist by spraying until the concrete has taken final set. (B) Wet Earth Cover 65. As soon as it can be done without damaging the concrete, the surface of the pavement shall be covered with not less than 2 in. of earth, or 6 in. of hay or straw. This cover shall be kept continuously wet by spraying for 10 days after the concrete is laid. (C) Sprinkling or Ponding 66. The sprinkling system of curing may be used if approved by the engineer. The sprinkling equipment shall be placed carefully, and without injuring the concrete surface. The sprinkling system shall be so arranged, and supplied with sufficient water at ample pressure, to keep every por- tion of the pavement surface continuously wet (both night and day) for 10 days after laying the concrete. Dikes shall be constructed along both edges of the pavement, with cross-dikes where necessary, and the water flowing off the surface of the pavement shall be collected and led to the ditches or culverts as directed by the engineer. The contractor shall be held responsible for any damage to the roadway, shoulders, or adjacent property, by reason of escaping water. 67. The ponding system of curing may be used at the option of the con- tractor. Dikes shall be built along both edges of the pavement, with cross- dikes at sufficiently frequent intervals, and the pavement flooded with sufficient water within the dikes to keep all portions of the pavement sur- face continuously covered with water for 10 days after the concrete is laid. (D) Cleaning 68. After 14 days, the earth or other cover may be removed. After 30 days, the contractor may use a mormon or a fresno scraper to remove the cover, except that scrapers shall not be used within 1 ft. of expansion joints. Cover within 1 ft. of expansion joints must be removed by hand. Road 308 CONCRETE PRACTICE machines, or blade graders of the 2- or 4-wheel type shall not be used for removing the cover. 69. After the cover has been removed, or ponds emptied and dikes removed, the entire surface of the pavement shall be swept clean and free from dirt and debris. Horse- or motor-drawn sweepers shall not be oper- ated on the pavement till 30 days have elapsed after the concrete is placed. (E) Cold Weather Protection 70. Concrete shall not be mixed nor deposited when the temperature is below freezing, except under such conditions as the engineer may direct in writing. If, at any time during the progress of the work, the tempera- ture is, or in the opinion of the engineer, will, within 24 hr., drop to 38°F. the water and aggregates shall be heated, and precautions taken to protect the concrete from freezing until it is at least 10 days old. In no case shall concrete be deposited upon a frozen subgrade, nor shall frozen materials be used in the concrete. XI. PROHIBITION OF TRAFFIC (A) Barricades 71. The contractor shall provide and maintain substantial barricades across the pavement, with suitable warning signs by day and by night, to prevent traffic of any kind upon the pavement before it is 21 days old, or before the cover has been removed. The contractor shall provide and maintain watchmen at each mixer, whenever the paving crew is not at work, who shall prevent destruction or removal of barricades, and keep traffic off the pavement. 72. No section of pavement shall be opened to traffic until written instruc- tions have been given by the engineer. (B) Crossings 73. At public highway and private crossings, the contractor shall pro- vide suitable structures to carry the traffic across the pavement without injury to the concrete. All such structures shall be subject to the approval of the engineer, and he may direct their improvement, or repair, as condi- tions may require. XII. CONDITION BEFORE ACCEPTANCE 74. Before the road will be considered completed in accordance with these specifications, and acceptable to the engineer, the pavement, shoulders, ditches, back slopes, and structures, shall be placed in a neat and orderly condition, conforming to the plans and specifications in all respects. Equip- ment, surplus materials, and construction debris of every description shall be removed from the aoe of way. - APPENDICES d09 TWO-COURSE PORTLAND CEMENT CONCRETE PAVEMENT FOR HIGHWAYS I. GENERAL 1. It is the intent of these specifications to cover the requirements for the materials and construction of Portland Cement Concrete Highway Pavements composed of two layers of concrete made with unlike coarse aggregates, but of the same proportions. II. MATERIAL 2. The requirements for (A) Cement, (B) Aggregates, (a) Fine aggregates, shall be as specified in Sec. II, (A), (B) and (a) one-course concrete highway pavement. 3. (b) Coarse Aggregate for Bottom Course.—Structurally sound material considered too soft for a pavement surface may be used as the coarse aggre- gate in the bottom course. It shall consist of crushed rock, pebbles (gravel), air-cooled blast-burnace slag, chatts, or tailings. The particles of coarse aggregate shall be of clean, durable material, free from vegetable or other deleterious substances, and shall contain no flat or elongated pieces. (Note: In many cases it will be necessary for the engineer to specify the sizes, grading, and quality of coarse aggregate in accordance with local conditions. In every case, the engineer should provide specifications which will require the use of the best coarse aggregate, which is economically available. The following specifications covering size and grading of coarse aggregate will be found applicable in most sections of the country and are intended for use with proportions from 1:2:4 to 1:114:3.) 4. The size of the coarse aggregate shall be such as to pass a 3-in. round opening. Coarse aggregate shall be uniformly graded within the limits shown in the following table, and any material which does not come within the limits specified shall be rejected. Passing 3-in. round opening, 100 per cent. Passing 2-in. round opening, not less than 82 per cent nor more than 95 per cent. Passing 14-in. round opening, not less than 15 per cent nor more than 25 per cent. Passing 14-in. sieve, not more than 5 per cent. 5. (c) Coarse aggregate for top course shall consist of crushed rock, pebbles (gravel), air-cooled blast-furnace slag, chatts, or tailings. The particles of coarse aggregate shall be of clean, hard, tough, durable material, free from vegetable or other deleterious substances, and shall contain no soft or elongated pieces. The crushed rock shall wear not more than 6 per cent when subjected to the standard Deval abrasion test. When subjected to the abrasion test described on page 30, U. S. Department of Agriculture, Bulletin 555, pebbles shall show a loss of not more than 12 per cent. 360 CONCRETE PRACTICE 6. The size of the particles shall be such that at least 95 per cent shall pass a l-in. round opening and not more than 5 per cent shall pass a 14-in. sieve, with all the intermediate sizes retained. 7. The requirements for Crushed rock, Pebbles (gravel), Air-cooled blast furnace slag, Chatts, or tailings, (d) Mixed aggregates, shall be as specified in Sec. II (B) one-course concrete highway pavement. 8. The requirements for _ (C) Water, (D) Reinforcement, (EK) Joint filler, (F) Shoulders, shall be as specified in Sec. II, (C), (D), (E), (F), one-course concrete high- way pavement. III. SUBGRADE 9. The requirements for subgrade shall be as specified in Sec. III, one- course concrete highway pavement. IV. FORMS 10. The requirements for forms shall be as specified in Sec. IV, one-course concrete highway pavement. V. PAVEMENT SECTION 11. Width and thickness of concrete pavement and the depth of the top and bottom courses shall be as shown on the plans for the improvement. VI. JOINTS 12. The requirements for joints shall be as specified in Sec. VI, of one- course concrete highway pavement. VII. WATER SUPPLY 13. The requirements for water supply shall be as specified in Sec. VII, of one-course concrete highway pavement. VIII. PROPORTIONING AND MIXING CONCRETE 14. (a) Measuring Materials.—The method of measuring the materials for the concrete, including water, shall be such as to insure the required proportions of each of the materials as directed by these specifications. One sack of portland cement (94 lb. net) shall be considered 1 cu. ft. 15. (b) Proportions.—The concrete in both the top and bottom course shall be proportioned 1 sack of portland cement, not morethan............ cu. ft. of fine aggregate, and not more than ............ cu. ft. of coarse S— APPENDICES 361 aggregate. A cubic yard of concrete in place, measured between neat lines PIMEHCONTAIN his. ca barrels of portland cement. The engineer shall compare the calculated amount of cement required by these specifications with the amounts actually used in each section of concrete............ ft. long, or between successive transverse joints. If the amount of cement actually used in the pavement varies from the specified amount by more than 3 per cent for any section, the engineer may require the proportions of the concrete to be adjusted so as to use the specified amount of cement. If it is found that the amount of cement used in any section is 9214 per cent or less, of the specified quantity, the contractor shall be required to remove such section or sections, and replace them with concrete made in accordance with these specifications. Such removal and replacement shall be done at the expense of the contractor. 16. The contractor may, at his option, construct the top course of mortar composed of cement and fine aggregate mixed in the proportion of 1 sack of CCS Pl 9 cu. ft. of fine aggregate. 17. The requirements for (B) Mixing, ‘ (a) Operation of mixer, (b) Retempering, (c) Central mixing plants, (d) Consistency, shall be such as specified in Sec. VIII, (B), (a), (b), (c), (d), one-course concrete highway pavement. IX. PLACING CONCRETE AND REINFORCEMENT 18. The requirements for ‘(A) Inspection of Subgrade, shall be as specified in Sec. IX, (A), one-course concrete highway pavement. (B) Placing Reinforcement 19. Steel fabric reinforcement of the size and weight shown on the plans shall be placed between the bottom and top courses, unless otherwise indicated. Fabric shall extend to within 2 in. of sides and ends of slabs. All laps of fabric sections shall be not less than the spacing of members in the direction lapped. Steel bar reinforcement shall be placed between the top and bottom courses unless otherwise indicated on the plans. Transverse bars shall extend to within 3 in. of the margins of the pavement. Bar reinforcement shall be placed and securely supported in correct position before any concrete is laid. All intersections of longitudinal and transverse bars shall be securely wired or clipped together to resist displacement during concreting operations. (C) Placing Concrete 20. The mixed concrete shall be deposited rapidly on the subgrade to the required depth and for the entire width between longitudinal joints, without 362 CONCRETE PRACTICE the use of intermediate forms or bulkheads between joints. While being placed, the concrete shall be vigorously sliced and spaded with suitable tools, to eliminate voids or honeycomb pockets. The concrete shall be especially well spaded and tamped adjacent to forms, bulkheads, and curbs. The bottom course shall be struck off at the correct elevation with a template or screed riding on the side forms. The top course shall be placed within 15 min. after the bottom course was placed. Any dust, dirt, or foreign matter which collects on the surface of the bottom course shall be carefully removed before the top course is placed. 21. Whenever, because of a breakdown or for any other reason, operations will be stopped for more than 30 min., a transverse joint shall be formed at the point directed by the engineer, to close the section. Both the top and bottom courses shall be completed to this joint. Any concrete in excess of that needed to complete a section, when work is stopped for morethan 30 min., shall not be used in the pavement. 22. The requirements for (D) Finishing shall be as specified in Sec. IX, (D), of specifications for one-course concrete highway pavement. X. CURING AND PROTECTION 23. The requirements for curing and protection shall be as specified in Sec. X, of specifications for one-course concrete highway pavement. XI. PROHIBITION OF TRAFFIC 24. The requirements for prohibition of traffic shall be as specified in Sec. XI, of specifications for one-course concrete highway pavement. XII. CONDITION BEFORE ACCEPTANCE 25. The Condition before Acceptance shall be as specified in Sec. XII, of specifications for one-course concrete highway pavement. OS INDEX A Aggregates (See also Fine aggre- gates, Coarse aggregates, and Sand). definition, 1 inspection, 188 sampling, 188 sieve analysis curves, 191 tests of bulking effect of water, 195 colorimetric test, 194 sieve analysis, 190 silt in fine aggregate, 193 standard method of test, organic impurities, 323 sieve analysis, 320 unit weights, 319 tentative method of tests, de- cantation test, 322 ,unit weights, 189 voids, 191 Appendices, 303 Aspdin, Joseph, 3 B Basement (See Concrete basement). Bridges (See Reinforced concrete bridges). Briquettes, dimensions, 317 molds, 317 Buckets, drop bottom, 70 Building units (See Concrete build- ing units). Buildings (See Reinforced concrete buildings). C Cement, 1 (Also see Portland cement). Cement mortars (See Portland - cement mortars). tests (See Portland cement tests). Cementing materials, 2 classification, 2 Coarse aggregates, 12 (Also see Aggregates). bulking effect of water, 14 definition of, 1 fineness modulus, 15 inspection, 13 kinds, 12 sieve analysis, 15 specific gravity, 14 specifications, 15, 180 unit weight, 14 voids, 14 Concrete (Portland cement con- _ crete), bonding new to old, 67 consistency, 47 tentative method of test for consistency, 329 definition, 1 depositing in forms, 66 effect of various oils and liquids on concrete and protective treat- ment required, 339 effect of various substances in concrete mixes, 23 effect of various substances on hardened concrete, 25 estimating, 154 materials (See Aggregates). computing quantities, 49 measuring, 48 by volume, 48 by weight, 49 inundation method, 48 tests required for, 212 363 364 Concrete mixers, 55 mixing, by hand, 51 by machine, 55 specifications for, 57 placing during freezing weather, 70 placing under water, 69 properties, 17 abrasion, 22 absorption, 22 compressive strength, 17 contraction, 22 expansion, 22 slump, 19 unit weight, 22 workability, 19 proportioning, 26 by arbitrary proportions, 28, 199 by Joint Committee table, 33, 200, 324 by sieve analysis and maximum density curve, 30 by surface area method, 32 by voids, 29 by water-cement slump, 35, 202 by water-cement ratio, slump, and fineness modulus, 38, 204 general rules and theory, 26 illustrative example, 43 protection in freezing weather, 72 protection while hardening, 68 slump, 37 test specimens—making and stor- ing in field, 335 testing machines used, 213 tests, consistency or slump, 198 effect of age, 211 effect of varying amount of mixing water, 205 effect of varying fineness modu- lus, 207 _ required for concrete materials, 219 standard methods of making compressive tests, 330 ratio and CONCRETE PRACTICE Concrete tests, tentative method of making consistency test, 329 transportation, 61 barrows, 61 booms, 63 buckets, 65 carts, 61 towers, 61 waterproofing, by adding integral compounds, 74 by proper proportioning, 73 by water proof coatings and membranes, 75 Concrete aggregates gates). Concrete arches (See Reinforced concrete arches). Concrete basement, concreting, 231 estimating, 225 excavation, 227 forms, 229 removal of forms, 232 staking out, 223 Concrete block (See Concrete build- ing units). Concrete brick (See Concrete build- ing units). Concrete bridges (See Reinforced concrete bridges). , Concrete building units, block, brick, and tile manufacture, 106, 298 curing, 108 dry tamp method, 107 pressure method, 108 - wet cast method, 108 Concrete building units, block, brick, and tile specifications, 110, 342 block walls, laying, 299 pointing, 302 Concrete culverts, 275 concreting, 282 estimating, 275 excavation, 280 forms, 281 placing reinforcement, 281 removing forms, 283 specifications, 275 (See Aggre- INDEX Concrete culverts, staking out, 280 types, 275 water area required, 276 Concrete cylinder molds, 336 Concrete floors, 271 specifications, 272 one course, 274 two course, 273 Concrete forms (See Forms). Concrete ornamental stone, 110 Concrete pavements, 245 crew organization, 252 curing, 259 design, 245 estimating, 245 forms, 251 mixing, 255 placing concrete, 255 plant, 252 proportions, 255 specifications, 245 standard specifications, 346 one course pavement, 346 two course pavement, 359 subgrade, 251 Concrete plant, 58 for arched bridges, 297 for paving, 252 for slab and girder bridges, 292 Concrete septic tanks, 263 Concrete sidewalks, 233 base, 234 concreting, 236 curing, 236 estimating, 233 finishing, 236 forms, 234 grade, 234 location, 234 specifications, 233 Concrete steps, 267 Concrete surface finish (See Surface finishing), 96, 101, 161 estimating, 161 granolithic, 102 mechanical finishing, 96 terrazo, 102 365 Concrete surface finish, wearing sur- face, 101 Concrete tile (See Concrete building units). Concrete trim stone, 110 Concrete wearing surfaces, 101 granolithic, 102 preparation, 101 terrazo, 102 Concrete window sills and lintels, 269 dimensions, 270 forms, 270 mix62 71 reinforcement, 270 Consistency of concrete, 46 (See Concrete consistency). Contracts, 115 definition, 115 kinds, 115 standard bridge contract, 116 bond, 117 contract, 119 proposal, 120 Culverts, 275 (See Concrete culverts). Curbs and gutters, 241 (See Concrete curbs and gutters). EK Estimating, 143-179 building costs (square and cube methods), 166 concrete basement, 225 concrete culverts, 280 concrete (materials, costs), 154 concrete pavements, 245 concrete sidewalks, 233 concrete surface finish, 161 excavation, 145 forms, 151 in general, 143 miscellaneous items, 163 labor and 366 Estimating miscellaneous items (block masonry, brick work, flooring, flashing, glass and glazing, heating, lighting, plastering, plumbing, roofing, sash, stucco) reinforcing steel, 158 sample cost estimate, 172 sample quantity estimate, 168 Excavation, basement, 227 culverts, 280 estimating, 145 F Field work, 218 (For list of field jobs see table of contents). inspection of, 218 supervision of, 220 Fine aggregates (Also see Aggre- gates). definition, 1 fineness modulus, 10 general, 8 sand, 8 bulking effect of water, 9 grading, 9 Ottawa, 10 sieve analysis, 10 silt test, 9 voids, 9 screenings, 11 specifications, 11, 129 Fineness modulus (See also Aggre- gates, Fine aggregates and Coarse aggregates). of aggregates, 38 of coarse aggregates, 15 _ of fine aggregates, 10 maximum practical values, 39 Finishing concrete surfaces, 96 (See Concrete surface finishing). Floors (See Concrete floors). Forms, depositing concrete in, 66 estimating, 151 for arch bridges, 293 for basements, 229, 232 CONCRETE PRACTICE Forms for buildings, 286 for culverts, 281 for girder bridges, 290 for pavements, 251 for septic tanks, 266 for sidewalks, 234 for slab bridges, 290 for steps, 268 for window sills and lintels, 270 in general, 77 metal, 91-95 Blaw, 92 Flore tyles, 95 Floredomes, 95 Metaforms, 93 Meyer, 95 . steel craft, 92 wall, 91 removal of form marks, 96 specifications, 134 wooden, column forms, 88 cost, 77 erection, 79 floor forms, 90 lumber sizes, 78 nails, 78 removal of, 80 rules for, 78 ties, 83 wall forms, 81 G Gillmore needles, 316 Girder bridges (See Reinforced con- crete bridges). Gravel, 13 (See Aggregate and Coarse aggre- gate). Gypsum plaster, 2 H Hand mixing of concrete, 51 Hydraulic cement, 2 Hydraulic lime, 2 INDEX I Inspection of aggregates, 188 concrete work, 218 portland cement, 183 L Laboratory (See Table of contents for list of laboratory jobs). methods, 180 reports, 181 work, 180 Le Chatelier apparatus, 308 Lime, 2 Lintels, 269 (See Concrete window sills and Lintels). M Machine mixing of concrete, 55 Measuring concrete materials, 48 Mixers, 55 a ie Mixing concrete (See Concrete). Mortars (See Portland cement mor- tars). N Natural cement, 2 O Ottawa sand, 10 B Parker, James, 3 Pavements (See ments). Plans, 137 abbreviations used, 138 complete plans, 137 reading plans and blueprints, 138 standard plans for concrete high- way bridge, 139 Concrete pave- 367 Plant (See Concrete plant). Plasters (gypsum), 2 Portland cement, 3 history, 3 inspection, 183 manufacture, 4 dry process, 5 quantity, 4 raw materials, 4 wet process, 5 properties, 5 fineness, 6 set, 6 soundness, 6 specific gravity, 7 strength, 6 standard specifications, 303 standard tests, 184, 303 Portland cement concrete (See Con- crete). Portland cement mortars, 7 properties, 8 strength, 8 weight, 8 proportioning, 7 tests, 196 Progress charts and reports, 175 Properties of concrete (See Concrete properties). Proportioning of concrete mixes (See Concrete proportioning). Puzzolanic cement, 2 i, Roman cement, 3 Reinforced concrete bridges, arches, 293 . centering, 293 forms, 293 plant, 297 pouring, 298 Reinforced concrete bridges, slab and girder bridges, 283 excavation, 283, 290 forms, 286, 290 foundations, 283 368 Reinforced concrete bridges, slaband Specifications, girder bridges, placing steel, 286 planning construction, 283 plans, 286 plant, 292 pouring, 288 Reinforcing steel (estimating), 158 S Sand (See Aggregates and fine aggre- gates). Ottawa, 10 standard test for organic im- purities, 323 tentative decantation test, 322 Saylor, David O., 3 Screenings, 11 Septic tanks (See Concrete septic tanks), 263 Sidewalks (See Concrete sidewalks). Sieve analysis (See Aggregates, Fine aggregates, Coarse aggregates and Sand). coarse aggregates, 15 curves, 191 fine aggregates, 10 sand, 10 test methods, 320 Sieves (specifications and sizes), 321 Slab bridges (See Reinforced con- crete bridges). Slag (See Aggregates and coarse aggregates). Slag cement, 2 Slump of concrete, 37 test, 47, 329 test apparatus, 329 Smeaton, John, 3 Specifications, coarse aggregate, 15, 130 concrete brick, 344 concrete building block and tile, 342 concrete curbs and gutters, 244 concrete floors, 272 concrete pavements, 245, 346 CONCRETE PRACTICE concrete sidewalks, 233 detailed, 121 fine aggregate, 11, 129 forms, 134 general, 120 mixing concrete, 57 proportions for concrete, 324 reinforced concrete highway bridge, 122 standard (See Appendices). concrete brick, 344 concrete building block and tile, 342 method of test for making and storing concrete specimens, 335 making compressive tests of concrete, 330 organic impurities in sand, 323 sieve analyses, 320 unit weights of aggregates, 319 portland cement, 346 surface finishing, 135 tentative (See Appendices). method of test for consistency of concrete, 329 decantation test for fine aggregates, 322 Standard Ottawa sand, 10 Steel forms (See Forms). Surface finishing (See Concrete surface finish). concrete floors, 271 concrete pavements, 257 concrete sidewalks, 236 estimating; 161 mechanical, 96 rubbing, 99 sand blast, 99 sand float, 99 scrubbing, 99 tooling, 99 washing, 99 specifications, 135 INDEX Surface finishing, use of colored aggregates, 100 use of pigments, 100 T Testing machines, 213 Tests (See Various headings). required for concrete materials, 212 Time and work schedules, 173 Transportation of concrete Concrete), 61 Tremie, 69 (See V Vicat apparatus, 311 Voids in coarse aggregates, 14 sand, 9 369 W Walls (rules for laying concrete, block walls), 299 Water, bulking effect on sand, 9 for concrete, 1, 16 Water proofing concrete by adding integral compounds, 74 applying water proof coatings and membranes, 75 proper proportioning, 73 Water-cement ratio (See Concrete) 35, 38 Wearing surfaces, 101 (See Concrete wearing surfaces). Window sills, 269 (See Concrete window sills and lintels). Wooden forms (See Forms). Work and time schedules, 173 Work in the field (See Field work). == ere ean en mene apie so tes nehthenani Aarne la! 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