uc SB Eh lift The D. Van Nostrand Company intend this book to be sold to the Public at the advertised price, and supply it to the Trade on terms which will not allow of discount. A MANUAL OF CEMENT TESTING FOR THE USE OF ENGINEERS AND CHEMISTS IN COLLEGES AND IN THE FIELD BY WILLIAM ALLYN RICHARDS, B.S. IN M.E. Instructor in the University of Chicago , Junior Member A *S.M.E. Member A merican Gas Institute, A merican Chemical Society AND HENRY BRIGGS NORTH, D.Sc. Associate Professor of Chemistry in Rutgers Collegt Member of the A merican Chemical Society A merican Electrochemical Society Societe chimique de France ILLUSTRATED NEW YORK D. VAN NOSTRAND COMPANY 25 PARK PLACE 1912 COPYRIGHT, 1912, BY D. VAN NOSTRAND COMPANY Stanbope jpress F. H. GILSON COMPANY BOSTON, U.S.A. PREFACE. IN order to insure uniformity of results in the testing of cement, it is essential that each test should invariably be made in precisely the same manner and under exactly the same conditions. A committee of the American Society of Civil Engineers has, with this aim in view, prepared and published a set of Standard Methods of Testing Cement, and these methods are to-day employed throughout the United States. This little volume, as its name implies, is a laboratory manual on cement testing, and is intended to assist in bringing about uniformity in the testing of cement. The authors have endeavored to present, in a somewhat con- densed form, such directions as will enable a student in the laboratory or an operator in the field office to correctly interpret the Standard Methods of Testing and Specifica- tions for Cement as published by the committee of the American Society of Civil Engineers, American Society for Testing Materials, Association of American Portland Cement Manufacturers, and the American Railway Engineers and Maintenance of Way Association; they have endeavored to give sufficient detail to enable all students to learn the same manipulations and thus be able to perform each test in a certain well defined and similar manner. ill 268767 IV PREFACE All of the tests described have been performed in the laboratory under the eyes of the writers and have been found to produce uniformly good results. Acknowledgment has been made to various authorities on the subject by special mention or as references at the end of the several chapters. Any corrections or suggestions will be gratefully received. W. A. R. H. B. N. June i5th, 1912. CONTENTS. PART I. PAGE INTRODUCTION ix CHAPTER I. CLASSIFICATION, COMPOSITION, MANUFACTURE. Definition Classification Portland Natural Pozzuo- lana Mixed Distinguishing Features Composition Silica Lime Alumina Iron Oxide Magnesia Sulphuric Acid Sulphur Alkalies Carbonic Acid Manufacture Raw Materials Cement Rock Limestone Marl Clay Chalk - Alkali Waste Mixing (Wet Process, Dry Process) Kilns (Stationary, Rotary) Grinding References i CHAPTER II. SAMPLING. Storage Collecting the Sample Sample Cans References . . 7 CHAPTER III. FINENESS. Importance Method Apparatus (Sieves, Scales) To Make the Test Results Deductions References 9 CHAPTER IV. SPECIFIC GRAVITY. Definition Significance Apparatus (Le Chatelier Specific Gravity Flask, Funnel, Chemical Balance) To Make the Test Calculation Cleaning the Flask Conclusion References ... 14 v vi CONTENTS CHAPTER V. NORMAL CONSISTENCY, MIXING, TIME OF SET. PAGE Significance Standard Apparatus (Vicat Apparatus, Scales, Burette) Mixing To Make the Test Time of Set Sig- nificance To Make the Test Conclusions References 20 CHAPTER VI. CONSTANCY OF VOLUME. Significance Kinds of Tests (Normal, Accelerated) Appara- tus (Boiling Apparatus) To Make the Tests Conclusions References 28 CHAPTER VII. TENSILE STRENGTH. Use Factors Affecting Strength Composition Fineness Amount of Water Apparatus (Molds, Testing Machines) To Make the Tests (Neat Cement) To Make the Test (Mortar) Determine the Percentage of Water Method of Mixing Breaking (Briquettes) Conclusions References 33 CHAPTER VIII. COMPRESSIVE STRENGTH AND TRANSVERSE TESTS. Compressive Strength Molds To Make the Test (Neat, Mortar) Breaking Conclusions Transverse Tests (Modu- lus of Rupture) Molds To Make the Test Breaking Calculations Conclusions References 41 CHAPTER IX. SAND AND STONE. Sand Test of Natural Sand Per Cent of Loam Mechani- cal Analysis Apparatus To Make the Test The Uniformity Coefficient The Effective Size To Find the Uniformity Co- efficient and Effective Size Voids Apparatus To Make the Test Stone Mechanical Analysis (Apparatus, To Make the Test) Voids (Apparatus, Specific Gravity, To Make the Test) References 49 CONTENTS vii CHAPTER X. LABORATORY EQUIPMENT. PAGE Special Apparatus Machines (Tension Test) Long Lever Shot Spring Balance Clips Transverse Tool Compres- sion Tool Universal Testing Machine Sand Shaker Scales and Balance Boiling Apparatus Moist Closet Storage Tanks Table Burette Molds (Briquette, Cube, Bar) - Miscellaneous Apparatus 63 PART II. INTRODUCTION Part played by Chemical Analysis; Preparation of Sample for Analysis 80 ANALYSIS OF CEMENT Determination of Loss on Ignition Silica (SiO2) Iron and Alumina (Fe 2 O 3 and A1 2 O 3 ) Lime (CaO) Magnesia (MgO) Sulphuric Acid (SO 3 ) Total Sulphur (S) Sulphur as Sulphide (S) Moisture Alkalies (K 2 O and Na 2 O) Carbon Dioxide (CO.) 84 ANALYSIS or LIMESTONE 106 ANALYSIS OF MARL 107 ANALYSIS OF SLAG 107 ANALYSIS OF CLAY 107 PART I. INTRODUCTION. THE Portland Cement Industry in the United States has had a most marvelous development. In 1880 the United States produced 82,000 barrels of Portland Cement, while in 1910 the output was estimated to be 70,000,000 barrels. This great increase in the use of cement is fitting testi- mony of its great value as a material of construction. Like all other materials used in construction, cement must be tested. Iron, steel, wood and stone, in their preparation for use or tests, have only their shapes changed ; but it is quite different with cement, which comes from the manufacturer to the testing laboratory, or wherever it is to be used, in the form of a fine powder, there to be mixed with water into a paste and deposited in forms till hardened into a solid. It is evident that of all materials of construc- tion subjected to a system of testing, cement is probably the most dependent on the judgment and skill of the person making the tests. It was with a view to eliminating this personal factor as far as possible, and thereby placing the tests of one operator, or one laboratory, on a basis of comparison with another operator or laboratory, that the American Society of Civil Engineers and several other societies appointed a committee to draw up specifications to be used in all tests of cement in the United States. X INTRODUCTION These specifications form the basis of this manual, and whenever the term " Standard Specifications," is used, it refers to the "Standard Methods of Testing and Specifi- cations for Cement," of the American Society of Civil Engineers. Classes. Cement tests are of two classes: (i) Experi- mental Tests, made for scientific purposes, and comprising such tests as modulus of elasticity, coefficient of expansion, etc., and (2) Routine Tests, made to ascertain if a certain consignment of cement will answer the requirements of a set of specifications, as regards soundness and strength. The routine tests usually employed are fineness, spe- cific gravity, soundness, tensile strength (both neat and sand), and time of set, while compression and transverse tests are sometimes used. The tests for soundness and strength are called primary tests, while fineness, specific gravity, etc., are called second- ary, since they give only additional information, which is of little value in itself. Routine tests alone will be considered in this work. CEMENT TESTING CHAPTER I. CLASSIFICATION, COMPOSITION, MANUFACTURE. Definition. Hydraulic cement is a material, which, when pulverized and mixed into a more or less pasty mass with water, has the property of setting or hardening under water. Classification. Cements are usually classified as follows : (i) Portland, (2) natural, (3) Pozzuolana, (4) blended or mixed. Portland cement is the finely ground powder of a clinker resulting from the incipient fusion of an intimate artifi- cial mixture of finely ground calcareous and argillaceous* materials, and must contain no materials added after cal- cination other than a small amount of calcium sulphate to regulate setting.! Natural cement is the finely ground powder of a clinker, * Calcareous partaking of the nature of calcite or calcium carbonate Argillaceous of a clayey nature. t This definition is sometimes further limited by stating: The finished product must contain at least 1.7 times as much lime, by weight, as silica alumina and iron oxide combined. ; C GEMENT TESTING resulting from the burning, at a heat below incipient fusion, of argillaceous limestone or other suitable natural rock. Pozzuolana cement results from grinding and mixing in definite proportions slaked lime and blast furnace slag, or certain volcanic lava. Mixed cement is, as the name implies, a cement made up of different brands or kinds of cements, and sometimes inert substances. Distinguishing Features. Natural or common cements are light or dark gray, according to the stone from which they are made. The specific gravity is from 2.7 to 3.0, with an average about 2.85. Portland cements have a specific gravity of from 3.0 to 3.5, averaging about 3.15. Natural cements have much quicker set and are lower in strength in the earlier tests. Pozzuolana cement made from slag is characterized chiefly by its light lilac color, absence of grit, low specific gravity (2.6-2.8), and by the intense bluish green color of a fresh fracture after long submersion in water. Composition. The basic elements of Portland cement are silica, alumina and lime. Ingredients such as iron, magnesia, alkalies, sulphuric acid, carbonic acid, and water also occurs in varying quantities, replacing some of the basic elements. The following represents about the limits within which fall the constituents of various American Portland cements, which pass the Standard Specifications for soundness, setting time and tensile strength: CLASSIFICATION, COMPOSITION, MANUFACTURE 3 Per Cent. Silica 20 to 24 Alumina 5 to 9 Iron Oxide 2 to 4 Lime 60 to 63.5 Magnesia i to 2 Sulphur Trioxide 1.5 The following represents an average: Per Cent. Silica 22.0 Alumina 7.5 Iron Oxide 2.5 Lime 62.0 Magnesia 2.5 Sulphur Trioxide 1.5 Silica (Si0 2 ). 19-24 per cent, exists in combination with lime as calcium silicate, which is an active hardening factor. It should not be present as free silica. Lime (CaO). 59-67 per cent, depending on the relative proportions of alumina and silica and care with which the cement has been manufactured. When in the combined state the greater the amount the stronger the cement. Excess of lime, or lime in the free state, will make an un- sound cement by expanding due to slaking. The more lime, the slower the setting. Alumina (A1 2 3 ). 5-10 per cent, mostly combined as calcium aluminate. The greater the proportion, the quicker the setting and the lower ultimate tensile strength. Le Chatelier believes calcium aluminate to be the greatest factor in hardening. Iron Oxide (Fe20s). Usually less than 4 per cent. Probably has little influence on the cement, though be- lieved by some to act the same as alumina. 4 CEMENT TESTING Magnesia (MgO). 2-4 per cent, by some considered as an impurity, while other investigators claim it acts the same as lime. Four per cent is placed as the limit by the Standard Specifications. Sulphuric Acid or Sulphur Trioxide (SOs). 1.25-1.75 per cent, due mostly to the introduction of calcium sul- phate into the finished cement to regulate setting. The more calcium sulphate (CaSO 4 ) the slower the set. It should never exceed 2-3 per cent, while the Standard Specifications limits it to 1.75. Sulphur (S). Found only in small amounts, usually comes from the coal used in burning the clinker, though sometimes from the raw materials. Sulphides, when in any considerable quantity, cause discolorations (dark blue spots) in the cement on hardening, and disintegration due to oxidation. Alkalies (K 2 O and Na20). 0.5-2 per cent, have little or no effect on cement unless in large quantities. Carbonic Acid (CO 2 ). 0.5-1.5 per cent, due mostly to absorption from the air; a large proportion shows under- burning or excess of lime. Natural and Pozzuolana Cements. The constituents of natural and Pozzuolana cements are practically the same as those of Portland cement, except that in the natural they are found in varying proportions. The following analyses* will serve to illustrate. * From Eckel's " Cement Materials and Industry." CLASSIFICATION, COMPOSITION, MANUFACTURE Portland. Natural. Pozzuolana. Silica 21 . ^O 26.40 28 o< Alumina 7.65 6.28 II .40 Iron 2.85 I .OO o. 54 Lime 60 (K 4< 22 ^O 20 M^agnesia 2 (K O OO 2 06 Sulphuric acid I 8l I 37 Alkali I . 1^ 4.00 Carbonic acid and water 7.86 2 . 7Q As the composition of natural cement from different plants, and frequently from the same plant, varies greatly, the analysis just given must not be considered as an aver- age, but simply as an illustration. MANUFACTURE. Raw Materials. The essentials, silica, lime and alumina, are obtained from six different sources. (1) Cement rock and limestone. (2) Limestone and clay. (3) Marl and clay. (4) Chalk and clay. (5) Slag and limestone. (6) Alkali waste and clay. Cement rock, from which about two- thirds of the cement manufactured in the United States is made, is an argilla- ceous limestone, low in magnesia. Marl, an almost pure calcium carbonate, is a soft, wet, calcareous earth. Clay is a more or less plastic substance composed chiefly of aluminum silicate, formed by the decomposition of minerals. 6 CEMENT TESTING Chalk, a soft, earthy variety of limestone or carbonate of lime, is usually of a yellowish-white color, but is some- times snow white. It is easily broken, has an earthy frac- ture, is rough, dry and harsh to the touch, and adheres slightly to the tongue. It sometimes contains a little silica, alumina, or magnesia, and occasionally all three. Limestone is a substance formed when clay has been deposited with calcareous matter. Alkali waste is the refuse from the manufacture of soda. It exists as caustic lime. These materials are very carefully analyzed and propor- tioned before mixing. The mixing is done in one of two ways, (i) by a wet or (2) by a dry process, after which the mixture is calcined. For this there are two kinds of kilns in use: (i) the stationary and (2) the rotary. Including the grinding of the clinker, the manufacture of cement, regardless of the process or method used, consists of three steps: (i) mixing and grinding, (2) calcining the mixture, and (3) reducing the clinker to a powder. REFERENCES. "Practical Cement Testing," by Taylor; "Concrete: Plain and Reinforced," by Taylor and Thompson; "Examination of Portland Cement," by R. K. Meade; "Manufacture of Portland Cements," by A. V. Bleininger; "Fourth Series," Bulletin 3, Ohio Geological Survey. CHAPTER II. SAMPLING. Storage. Cement is shipped in wooden barrels, cloth or paper bags, none of which furnish very good protection for its contents. Therefore, it is necessary to provide a good dry storage place. Inspection. The material, the condition of the packages, and, if possible, the transporting medium of each shipment should be thoroughly examined. Be very careful in the ex- amination of the storage room or warehouse. It must be dry and free from leaks. All packages should bear the manu- facturer's name or trade-mark, and any unmarked packages should be rejected. If the specifications call for sealed packages, all packages should be sealed and all seals should be similar. The cement should contain no hard lumps, as these indicate injury from moisture, which has caused partial set. Soft lumps easily broken by the fingers indi- cate aging, which is not harmful. It is well to ascertain the average weight of the packages. Collecting the Sample. The selection of the sample for testing must be left largely to the discretion of the party taking it. The quantity must depend upon the importance of the work and the number of tests to be made, as well as the facilities for making them usually 8 to 10 pounds. 7 8 CEMENT TESTING The sample must be a fair average of the shipment and also of the package. One barrel in ten is a fair average for a large shipment, but on small work or in small shipments samples should be taken more often; and never less than five bags should be sampled. To obtain an average of the shipment, the samples should be taken from packages in different parts of the pile. An average of the package is K obtained by means of a sampling auger (Fig. i), such FIG i as is used by butter or sugar inspectors, inserting it from top to center in bags, and from side to center in barrels, midway between the heads. Sample cans * marked with all necessary information as to the shipment, brand, manufacturer, etc-., should be used to store the sample in, until tested. Each sample should be thoroughly mixed and passed through a sieve having twenty meshes per linear inch, in order to break up lumps and remove foreign material and further mix the sample. REFERENCE. "Practical Cement Testing," by Taylor. * Mason (fruit) jars make good sample jars. CHAPTER III. FINENESS. Importance. In itself, fineness is of little importance, but because it affects the other properties it becomes of considerable moment. In the early stages of hardening only the finer particles have any effect, as water is slow in reaching the interior of the larger particles, thereby delaying the hydraulic action. Also, the finer particles will more easily cover the sand grains, making mortar much stronger, and allowing the use FIG. 2. of a larger percentage of sand. Neat cement mixtures are usually less strong with fine than with coarse cement. Seasoning can take place more easily with finely ground cement; because of this, fine cement is less liable to un- soundness. 9 10 CEMENT TESTING Method. Fineness is determined by passing the cement through sieves (Fig. 2) ; other methods by means of currents of air or liquids have been proposed but are little used.* Apparatus. Sieves, numbers 20, 50, 100 and 200, pan and cover, shot and scales. The sieves should be circular, between 6 and 8 inches in diameter and i\ inches deep, provided with a pan 2 inches deep, and a cover. The wire cloth should be woven from brass wire having diameters as follows : Inches. No. 20 0.034 No. 50 0.0090 No. zoo 0.0045 No. 200 0.0024 The cloth should be mounted on the frames without dis- tortion; the mesh should be regular in spacing and within the following limits : No. 50 not less than 48 nor more than 50 per linear inch. No. 100 not less than 96 nor more than 100 per linear inch. No. 200 not less than 188 nor more than 200 per linear inch. * "The classification of coarse materials according to size is very readily accomplished by means of sieves." But with cement and other fine materials a large proportion will pass the finest sieve; it is, therefore, desirable to have some way of separating these very fine particles. "It is well known that homogeneous substances fall in liquids with a speed that varies with their size, that is to say, the larger fall more rapidly than the smaller ones; and if a stream of liquid can be given a definite upward flow, certain relatively coarse particles will settle out and other relatively fine particles will be floated away." Classifiers for laboratory use have been made for the separation of fine particles, but the experiments so far take from two to four hours, and for cement are otherwise not entirely satisfactory. See article by G. W. Thompson, Proc. Am. Socy. for Testing Materials, 1910, vol. x, p. 601, also Taylor's " Practical Cement Testing, " p. 64. FINENESS II Scales. The scales used in tests for fineness should be sensitive to 5 centigrams. Figs. 3 and 4 show the two types generally used. That shown in Fig. 4 is designed especially for fineness tests. The beam is graduated so as to represent percentages of 50 grams.* To Make the Test. Weigh out 50 grams of the FIG. 3. thoroughly dried and coarsely screened sample, and place in the No. 200 sieve with about 200 grams of rather coarse shot. Then, FIG. 4. with pan and cover attached, hold all in the hands in a slightly inclined position, and move backward and forward, * The cuts for Figs. 3 and 4 were loaned by the E. H. Sargent Co., of Chicago. 12 CEMENT TESTING changing the plane of inclination, and allowing the sieve to strike the palm of the hand a sharp blow, squarely on the side, at the rate of about two hundred strokes a minute, for ten minutes. Empty the cement that has passed the sieve, clean the pan, and shake for one minute more.* When the amount passing the sieve in one minute of con- tinuous shaking is less than o.i per cent (0.05 gram), the residue is passed through the No. 20 sieve, to separate it from the shot, and is weighed. This weight in grams, multiplied by 2, gives the per cent retained on the No. 200 sieve. Place the residue on the No. 100 sieve and con- tinue the operation as above. Results should be reported to o.i per cent on forms similar to the one shown at the end of the chapter. A convenient method of determining when less than o.i per cent has passed a sieve is to weigh out 0.05 gram of cement; form it into a compact heap and lay it aside for reference. Then, by comparing the cement being tested with this, it can be told at a glance if the shaking should be continued. The difference in color and structure between the several residues should be observed and noted. Deductions from Test. Specifications generally state that for natural cement a residue of not more than 15 per cent shall be left on the No. 100 sieve, nor 30 per cent on * Should the residue after the one minute of continuous shaking be greater than o.i per cent the operation must be continued till not more than o.i percent remains on the sieve after one minute of continuous shaking. FINENESS the No. 200 sieve; and for Portland cement not more than 8 per cent on the No. 100, nor 25 per cent on the No. 200 sieve; but unless the cement acts badly in the other tests it is not well to reject a cement, except when variation from these requirements is great. REFERENCES. "Taylor's Practical Cement Testing," pp. 75-78; Johnson's " Materials of Construction," Art. 310; "Standard Methods of Testing and Specifications for Cement," Pars. 19-27. FINENESS. Apparatus Condition of Sample Brand Ho. Weight of A/G Weight ^o fie- Pefa'inecl hxineoi JZefarxxf tarmecf Remarks CHAPTER IV. SPECIFIC GRAVITY. Definition. The specific gravity of a substance is the ratio of the weight of a given volume of that substance to the weight of an equal volume of water. In the metric system it is the ratio of the weight of the substance in grams to its volume in cubic centimeters. Significance. " The specific gravity of cement is lowered by adulteration and hydration, but the adulteration must be in considerable quantity to affect the results appreciably." As the differences in specific gravity are usually very small, every precaution must be taken to make the results accurate. At the best, it is now believed, the test is of but little value, as can be seen from the following, which are the conclusions reached by R. K. Mead and Lester C. Hawk after a series of experiments.* " The specific gravity test is of no value whatever in detecting underburning, as underburned cement will show a specific gravity much higher than that set by the stand- ard specifications. Underburned cement is readily and promptly detected by the soundness tests, and no others are needed for this purpose. * Proceedings of the loth annual meeting of the Am. Socy. for Testing Materials, vol. vii, p. 363. 14 SPECIFIC GRAVITY 15 " The value of the specific gravity test as an indication of adulteration is much exaggerated. While a large admix- ture of any light adulterant with the cement would be shown, there is at the same time much slag and also Rosendale cement which could be mixed with cement in large quantities without lowering the specific gravity below the limit of our standard specifications. " Low specific gravity is usually caused by sea- soning of the cement or clinker, either of which improves the product. "'The proposition to ignite the cement sample which falls below specifications and determine the specific gravity upon the ignited portions is of no value because adulterated cements also have their specific gravity very much raised by such ignition." Apparatus. Le Chatelier specific gravity flask, glass funnel, ring stand, settling jar, glass rod and pipette (Fig. 5), chemical balance (Fig. 20). Various forms of specific gravity flasks have been devised, most of them on the same principle; but the one now used almost exclusively is the Le Chatelier apparatus (Fig. 6). This consists of a flask (a) of 120 c.c. capacity, with a neck (6) about 9 mm. in diameter and 20 cm. long, which has a bulb (c) at the middle, with graduation marks immediately above and below; the volume between these marks is 20 c.c. The neck, from the mark above the bulb i6 CEMENT TESTING for about 6 cm., is graduated into tenths of a cubic centi- meter. To Make the Test. Fill the Le Chatelier flask with benzine (62 Baume naphtha) to the lowest mark, taking care not to wet the side of the neck above the bulb. Let this stand while 65 grams* of the cement to be tested is weighed out on a chemical balance. With a pipette, adjust the lower meniscus exactly to the mark under the bulb taking care to avoid parallax by sighting on a distant horizontal line of about the same level as the eye. Support funnel (a) by a ring stand (&), (Fig. 7), allowing the stem to project into the flask about one inch. A pad of paper should be placed under the flask for protection from breaking. Introduce the cement all at one time into the funnel, holding a glass rod in the bottom to control the dis- charge of the cement. By slightly raising and lowering the glass rod, a small portion of the cement will pass through * While the Standard Specifications give 64 grams the authors have been in the habit of using 65 grams. Other cases are known in which the test is made with 65 grams of Portland or 64 of natural cements. Poet, FIG. 7. SPECIFIC GRAVITY 17 the funnel into the flask; and by slightly jarring the flask on the paper pad, all of the cement may be made to pass to the bottom of the flask with almost perfect elimination of air, thereby displacing the benzine. See that all of the cement enters the flask, by brushing scale pan, weighing paper, rod and funnel. The funnel used in introducing the cement must be perfectly dry; otherwise some of the cement will be prevented from entering and the test will be spoiled. The displaced benzine rises to some division in the graduated neck, as 0.8, shown by the line in Fig. 7; and this plus 20 c.c. (the vol. of bulb), making 20.8 c.c., is the volume of the 65 grams of cement; and ~ p _ weight of the cement _ 65 gms. _ displaced volume 20.8 c.c. To prevent evaporation the flask should always be grasped above the benzine. The room should be cool and free from air currents. The flask may be immersed in water to keep it at a constant temperature. Cleaning the Flask. To empty the flask, shake it vigorously to loosen the cement, then invert quickly over a large jar and shake with a vertical motion. Add a small amount of clear benzine and repeat the operation until all the cement is removed.* The benzine should be filtered and used again. * A thorough cleaning of the lower bulb is not necessary between tests, but the neck must always be kept clean. l8 CEMENT TESTING Conclusion. In order to draw conclusions from a specific gravity test, the operator must be familiar with the specific gravity of the brand of cement he is working with, as different brands vary greatly. When a sample tests below the known average of the brand it must be subjected to further examination for adulterants, and an additional specific gravity test should be made on an ignited sample, to see that the low specific gravity is not due to excessive seasoning. The final rejection or acceptance must be based on the results of the strength tests, modified by the specific gravity, as the experience of the operator indicates. REFERENCES. Taylor's "Practical Cement Testing," pp. 46-51, 58-63; John- son's, "Materials of Construction," Art. 311; "Standard Methods of Testing and Specifications for Cement," Pars. 8-19. SPECIFIC GRAVITY SPECIFIC GRAVITY. Apparatus Condition of Sample Brand fa Wefyhf 6>f Sample frtcre&fe of Vo/ume $p*cffic Gr&v/ty Average Remarks CHAPTER V. NORMAL CONSISTENCY, MIXING, TIME OF SET. Significance. Different percentages of water used in making the pastes,* for soundness tests, setting tests, briquettes for strength tests, etc., cause the same sample of cement to give widely varying results. Likewise, these results are affected by a difference in the amount of working that the pat receives. Therefore, it is necessary to fix some standard by which the amount of water may always be kept uniform, and the amount of working always the same. Standard. The standard requires the use of such a quantity of water as will, with a definite amount of working, reduce the cement to a certain state of plasticity, called normal consistency. The plasticity recommended by the Standard Specifications is such that the plunger of a Vicat apparatus will sink to a point in the mass 10 mm. below the top of the ring. Apparatus. Vicat apparatus, scales, glass plate and rub- ber ring, burette (Fig. 8 or Fig. 36). The Vicat apparatus is the one now used almost entirely. This consists of a frame (k), (Fig. 9), in which a rod (/) moves. There are two caps (a and d) which may be placed on the upper end of * The term paste is used to designate a mixture of cement and water, and the term mortar a mixture of cement, sand and water. 20 NORMAL CONSISTENCY, MIXING, TIME OF SET 21 the rod (/) and a needle (k) i mm. in diameter, or cylinder (b) i cm. in diameter (0.39 in.), at the lower end and held by a thumbscrew (g). The caps (d and a) are of such weight that when used with the needle or cylinder respectively, their FIG. FIG. 9. weight together with the rod (/) is 300 grams. To the rod (/), which can be held in any desired position by the thumbscrew (/), is attached an indicator, which moves over a scale (graduated to millimeters) attached to the frame (k). The paste is placed in a rubber ring (i) 4 cm. high and 7 cm. in diameter at the base and slightly tapering to the top, resting on a glass plate (/) about 10 cm. square. Mixing. Weigh out 500 grams of cement and form it into a crater about 4 inches in diameter (Fig. 10). For first trial, into this crater pour, all at one time, a quantity 22 CEMENT TESTING of water equal in amount to about 20 per cent of the weight of the cement. With a trowel turn the cement from the outside edges, into the water, a little at a time, till the crater is filled and the water is absorbed. This should take about a minute's time. Now turn this mixture over two or three times with the trowel to distribute equally the wet cement, and form into a pile. Knead the mixture vigorously for 1 1 minutes, much as dough is kneaded for bread. The process is best described as follows : Place the hands, with the fingers and thumbs touching, over the top of the pile, the wrists resting on the table. Then push rapidly forward with a downward pressure of about 15 pounds and at the same time close the fingers in, so as to squeeze the pile. Do this two or three times. Then turn the pile at an angle of 90 degrees and continue the kneading. At the end of a minute and a half, form the paste into a ball and toss from one hand to the other six times, holding the hands 6 inches apart.* To Make the Test. Press the ball into the large end of the rubber ring of the Vicat apparatus, smooth off and place on a glass plate with the large end down. Smooth the top with a trowel, using light pressure. Place the ring under the Vicat plunger; set the plunger in contact with * To secure uniformity of results, these directions must be followed to the letter. NORMAL CONSISTENCY, MIXING, TIME OF SET 23 the surface, read the scale and quickly release the plunger. Take the final reading on the scale when perceptible motion has ceased. The paste is of normal consistency when the plunger penetrates 10 mm. below the surface. If the correct penetration is not obtained, discard the sample and make another trial, using more or less water as re- quired. Continue until the right percentage of water is found. Record on blanks similar to the one shown at the end of the chapter. The Vicat apparatus must always be kept exceptionally clean. During all mixing operations the hands should be pro- tected with rubber gloves. TIME OF SET. Significance. The time of set gives no indication of the strength or soundness of a cement. But it is very important to know the time of initial set (the time which elapses from the moment water is added to the cement until the paste ceases to be plastic, or when crystallization begins), and final set (the time taken to become a hard mass). Handling the cement after it commences to set, or after the process of crystallization or hardening has begun, will weaken it and cause it to disintegrate. It is, therefore, very important to know how long a time may be allowed in mixing and placing a batch of cement without injury to 24 CEMENT TESTING it, and after it is placed how long it will take it to harden so that the forms may be removed. It should harden as quickly as possible after initial set. It usually takes con- siderable time for mixing and placing concrete (the form in which cement is most generally used) ; therefore, a cement should have a slow " initial set " but reach " final set " soon after. These periods are arbitrarily measured by the penetration of weighted wires of given diameter, as the needle of the Vicat apparatus. Things Affecting the Time of Set. Fineness, allowing the water to reach the interior of the particles more easily, increases the rapidity of setting. Long standing cements absorb moisture from the air and lose their hydraulic property. The greater the amount of water used in mixing, the slower will be the set. Increased temperature of the mixing water hastens the time of set. To Make the Test. The Vicat apparatus with needle is used. Mix 500 grams of cement to a paste of normal consistency. Record the time of adding the water. Place the paste in the Vicat ring as in normal consistency tests, bring the Vicat needle into contact with the surface, and release quickly. Find to what mark the needle should descend to be 5 mm. from the bottom of the ring. Release needle at intervals till set occurs. Initial set is said to have occurred when the needle NORMAL CONSISTENCY, MIXING, TIME OF SET 25 ceases to penetrate beyond a point 5 mm. from the bot- tom, and final set when it makes no indentation. Always see that the needle and apparatus are clean. If Portland and natural cements are to be tested at the same time, mix the Portland first, as it requires more time to attain set. Test Portland cement for initial set after 15 minutes, and natural after 5 minutes. The rings with the samples being tested should be stored in a damp closet during the test. Conclusions. Time of set being influenced by so many conditions, tests made by the' same operator often do not check closer than 10 per cent and by different operators vary even more. Therefore, considerable allowance should be made in judging a cement for time of set. It requires from 20 to 30 minutes to mix and place a batch of concrete in large work, but it also takes much longer to set than in the tests; so that, in general, a cement need not be rejected unless the mixing and placing on the work takes two or three times as long as the test set. REFERENCES. Normal Consistency. Taylor's, "Practical Cement Testing," pp. 92 to 95, 120 to 126; Johnson's, "Materials of Construction," Arts. 316, 318; "Standard Methods of Testing and Specifications for Cement," Pars. 27, 37, 52, 59. Time of Set. Taylor's "Practical Cement Testing," pp. 80 to 83, 88 and 89; Johnson's, "Materials of Construction," Arts. 164, 312, 421; "Standard Methods of Testing and Specifications for Cement," Pars. 37 to 44. 26 CEMENT TESTING NORMAL CONSISTENCY. Temperature of Temperature of Humidity Mixii Room ig Water -, Mo. 'of Per Cent of Water *-* Remarks .. NORMAL CONSISTENCY, MIXING, TIME OF SET 27 TIME OF SET. Apparatus Temperature of Room Temperature of Mixing Water . . Humidity 1 1 A ^^k fcli ^t Initia/ $*f /V>7^/ ^/ 355? 77>77

% * 7 14 tl 28 Pat-$ /n water 7 14 71 28 Condition of Ball Condition of Pat steamed 3 Hours Conclusions CHAPTER VII. TENSILE STRENGTH. Use. Cement is used in compression, but since there is a certain fairly definite relation between its strength in compression and tension, the accepted method for deter- mining this strength is the use of a tensile test, which is the test most easily performed. It is made by mixing the cement into a paste, or the cement and sand into a mortar, and molding into test specimens or briquettes, which are allowed to set and are tested at the end of i, 7 and 28 days, or, in some cases, at longer intervals. Strength tests of mortar briquettes are of much greater importance than are neat cement tests, as it is in the form of a mortar that cement is used. FACTORS AFFECTING STRENGTH. Composition. Aluminates are presumably responsible for the setting, and silicates for the final hardening; there- fore, high aluminates will give a cement a higher early strength and a lower ultimate, and vice versa. Aging. Cement should not age longer than necessary for manufacture, as this will lower the initial strength and, if it is allowed to continue much longer, the ultimate strength. 33 34 CEMENT TESTING Fineness. Fineness will, in general, weaken neat cement, but will strengthen sand mortar. This increase in strength of sand mortar is due to the fact that fine cement more thoroughly covers the sand grains, while in the neat the weakening seems to be due to the fact that, in a coarse briquette, the line of break passes around, rather than through the grains, thereby increasing the breaking area. Amount of Water. The amount of water used in mixing and the method employed seem to affect the strength of the cement greatly. (Chap. V.) Apparatus. Briquette molds, either single (Fig. 13) or gang (Fig. 14), glass plate the size of the mold. To Make the Test. (Neat Cement.) Weigh out 800 grams of cement (which will make 5 bri- quettes), mix to normal consistency and fill the molds as FIG. 13. FIG. 14. follows. (The molding of the briquettes is perhaps the most important factor in cement testing.) Place a well-oiled mold on an oiled glass plate,* sides toward the operator, put enough cement to half fill the molds into each opening, and press it lightly and evenly * Plate should be of the same width as the outside of the molds and enough longer tc rest on the cleats of the damp closet to be used. TENSILE STRENGTH 35 into the bottom of the molds. Do this with the fingers and thumbs, never with a tamper of any sort. Place enough cement in and above the molds to more than fill them; turn the molds 90 and begin at the end farthest away to press, without ramming, the cement into the molds with the thumbs, gripping the sides of the molds with the fingers so as to exert a pressure of about 25 pounds. Press each briquette in this manner three times, once at each end and once in the middle. Turn the mold back to the original position, add more material and smooth off with a trowel, using about 5 pounds pressure. The smoothing should be a cutting action, taking away the excess material and yet filling in all the openings. With a few final strokes of the trowel, make the surface perfectly smooth and press the cement well up to the sides. Place a glass plate on top and turn the mold over, and smooth the bottom in the same manner as the top, by adding material and troweling. The mold resting on the glass plate is now placed in a damp closet for 24 hours, when the briquettes are removed from the molds and stored on edge in water. They must remain here until they are to be broken, which should be done immediately after removal from the water. Make enough briquettes so that five may be broken at each period called for, usually i, 7 and 28 days, though often the i-day tests are omitted. 36 CEMENT TESTING MORTAR BRIQUETTES. To Make the Test. Weigh out materials as follows:* For Portland cement, i to 3 mortar, cement 250 grams, sand 750 grams. For natural cement, i to 2 mortar, cement 300 grams, sand 600 grams. Determine the percentage of water by Taylor's formula, as follows : 4 (n + i) where X = per cent of water for the sand mixture; N = per cent of water for the neat cement ; n = parts of sand to one of cement by weight; S = a constant depending on the character of the sand and consistency desired. (For Ottawa sand, S = 25; for bar sand, 5 = 27 to 33; usually use 33.) The method of mixing and filling the molds is the same as for the neat briquettes, except that the amount of water is determined as above, and the cement and sand are mixed dry to a uniform color before forming into a crater. Make six briquettes of each cement, three to be tested at each period of 7 and 28 days. Briquettes should be stored in water in a damp closet (the same as the neat), after being marked with the necessary information as to brand, proportions of sand, etc. * This amount should be sufficient to fill 4 3-gang molds. TENSILE STRENGTH 37 BREAKING. Test pieces must be broken as soon as they are taken from the water. Any standard machine (Figs. 21-25) may be used, but it should be supplied with the solid metal clips (Fig. 15), as they are the ones recommended by the Standard Specifications. Clips should be used without cushioning the points of contact. Great care must be observed to center the briquettes in the clips and to see that they are free from sand, in order to avoid cross-strains, which cause clip breaks. Apply the load slowly, as a suddenly applied load may produce vibration or shock, which will cause the briquette to break before the ultimate strength is reached. The Standard Spec- ifications recommend that the rate of application of pressure be 600 pounds per minute. The average value of the briquettes of one sample broken should be taken, with high or low results excluded. Conclusions. A cement, to be acceptable, should fulfil the following conditions in the tension test: " (i) Both neat and sand briquettes shall pass a minimum specified amount at 7 and 28 days. (2) That the neat value at 7 days shall not be excessive. (3) There shall be no falling off between 7 and 28 days in neat test. (4) Sand tests must show an increase of at least 10 to 15 per cent. (5) Sand tests are the true tests of the strength. A cement failing in sand FIG. 15. 38 CEMENT TESTING tests should be rejected even if it passes the neat test. When the reverse is true, i.e., when it passes the sand test and fails in the neat, cement may be accepted if no signs of unsoundness have developed." The following rules, given by Taylor in " Practical Cement Testing," should be followed. " At 7 days: Reject on a decidedly low sand strength. Hold for 28 days on low or excessively high neat strength, or a sand strength barely failing to pass requirements. "At 28 days: Reject on failure in either neat or sand strength. Reject on retrogression in sand strength, even if passing the 28-day requirements. Reject on retrogres- sion in neat strength, if there is any indication of poor quality, or if the 7-day test is low; otherwise accept. " Accept if failing slightly in either neat or sand at 7 days and passing at 28 days." REFERENCES. For Neat. Taylor's "Practical Cement Testing," pp. 120-125; Johnson's, "Materials of Construction," Arts. 315, 316, 319, 320, 323, 324 and 325; "Standard Methods of Testing and Specifications for Cement," Pars. 59-69. For Mortar. Taylor's "Practical Cement Testing," pp. 108, 114, 120-125; Johnson's "Materials of Construction," Arts. 317-319, 406-411; Taylor and Thompson's "Concrete: Plain and Rein- forced," pp. 132, 133; "Standard Methods of Testing and Specifica- tions for Cement," Pars. 35-36. TENSILE STRENGTH 39 TENSILE STRENGTH. (Neat Cement.) Machine used for Breaking Per cent of Water used in Mixing.. Aye Brarnaf Afo. 5r&r?af f\fo. 7er75//e $fre/7q/h Pev/artier? from Mearr? 7ef?s//e $trer?gJJ? Pe war tier? frem Macrr? Rrunds Per- Cent founds frr&nf 7 Pays Mean Remarks CEMENT TESTING TENSILE STRENGTH. (Mortar.) Machine used for Breaking... Brarnef .* Cement * ll ^ ** a* ll 75/75/%P Zfrengfh Deviation from Mean. Pounds Per Cent Pays 28 Pays P0r/ ?8 Pays Pay* ~z.e Pt*y*^ / / Remarks CHAPTER VIII. COMPRESSIVE STRENGTH AND TRANSVERSE TESTS. Compressive Strength. In the United States, compres- sion tests are not used as standard tests for the reception of a cement, but where a concrete is required to be tested, or where a comparison test of different sands and stones that are to be used in concrete is to be made, the com- pression test is necessary as the size of the aggregate requires the use of larger specimens than the regular bri- quettes of the tension tests. The form and size of the specimen most generally used are two-inch cubes for mortar and six-inch cubes for con- crete. Cylinders six inches in diameter and ten inches to twelve inches deep are preferable for concrete because the ease of rilling and packing them makes the specimens of this size more uniform. In order that there may be proper contact between the testing machine and the specimen, the bearing surfaces of the specimen should be smoothed to true planes, and to correct any slight angle between the bearing surfaces, one surface should rest on a plate having a ball and socket joint. Blotting paper or plaster of Paris should be placed be- tween the block and the machine to counteract the irregu- 41 42 CEMENT TESTING larities in the specimen; this will, however, slightly lower the strength. Molds. Four gang 2-inch cube molds (Fig. 16) are gen- erally used, but the size depends to some extent on the capacity of the machines obtainable for breaking the specimens. To Make the Test. Oil the molds and glass plate thor- oughly before mixing. Neat. Weigh out 900 grams of cement (if 2-inch cubes are to be used) and mix by standard methods, as given FIG. 16. under Normal Consistency. Fill the molds in a manner similar to that described for briquettes, mark and place in the damp closet for 24 hours. Remove the cubes from the molds and place in water. Do not take from the water until ready to break. Test the cubes at the end of 7 and 28 days. Mortar. Weigh out 400 grams of cement and 1 200 grams of sand for 1:3 mortar, or 550 grams of cement and 1 1 oo grams of sand for i : 2 mortar. Determine the amount of water to use and fill the molds, following directions given for mortar briquettes. Place in a damp closet, remove from the molds, store and break, using directions given under Neat. COMPRESSIVE STRENGTH AND TRANSVERSE TESTS 43 Breaking. Use an ordinary universal testing machine (Fig. 29) of 30,000 capacity (for 2-inch cubes), with com- pression tool in the moving head. Place the cube exactly in the center of the machine. (This can be done by means of the circles cut in the table of the machine.) Run the head down until nearly in contact with the cube, with medium speed; change to the slowest speed and apply load, keeping the beam balanced until the cube yields under the load. Conclusion. The results of compressive tests are to be interpreted in accordance with the same general rules as for tension tests. There is a ratio between compression and ten- sile strength, which varies from 5 to 10 for average results.* TRANSVERSE TESTS. (Modulus of Rupture.) Molds. The molds for this test are usually i-in. by i-in. by i3-in. beam molds, though sometimes i^-in. by ij-in. by i3-in. or 2-in. by 2-in. by i3~in. molds are used; 6 beams will give a very good average result. Fig. 17 shows a gang mold. To Make the Tests. Oil the molds and the glass platef thoroughly. Weigh out 1000 grams of cement; mix and fill the molds in the same manner as for briquettes or cubes. When using gang molds do not try to turn the molds over, * See discussion in "Materials of Construction " by J. B. Johnson, and Practical Cement Testing, p. 215. t If glass plate large enough for gang mold is wanting, a water-soaked asbestos board may be used. 44 CEMENT TESTING but use extra precautions to see that the cement fills the bottom of the molds. Place in damp closet for 24 hours; remove from the molds and place in storage water for 7 days, and then break. FIG. 17. Breaking. Beams should be broken on the long lever testing machine with special attachment (see description on p. 70), using, if possible, a 1 2-inch span. Should any beams be broken in handling before being tested, they may be broken at shorter spans. Reports of this test should include the calculations. Calculations. The modulus of rupture is calculated by the formula i W L R = ^77;' which for i-inch square specimens becomes R=$W.L,m which 2 W = the center load in pounds, L = the length of span in inches, B = width of the specimen, H = the depth. COMPRESSIVE STRENGTH AND TRANSVERSE TESTS 45 Illustration. Suppose a beam i in. by i in. on a 1 2-inch span breaks with a center load of 50 pounds; then R = $W.L = - X 50 X 12 = 900 inch-pounds. 2 2 Another beam 2 ins. by 2 ins. on a 1 2-inch span breaks with 400 pounds, center load. 3 -W.L 3 X 400 X 12 R = : = = ooo inch-pounds. 2-B.H 2 2X2X4 Conclusion. There is a ratio* between transverse strength and tensile strength varying between 1.3 and 2.5. By assuming an average of 1.5 and multiplying the modulus of rupture by this average, an approximate estimate of the tensile strength may be obtained. However, this is rather unsatisfactory, since transverse specimens are subject to so many variations. A cement should never be condemned by a transverse test alone, unless a series of tests shows a very low value. REFERENCES. Compression Tests (Neat). Taylor's "Practical Cement Testing,'* pp. 212-216; Johnson's "Materials of Construction," Arts. 280, 315, 326. (Mortar) Taylor, pp. 212-216; Taylor and Thompson's "Con- crete: Plain and Reinforced," p. 136; Sabin's "Cement and Con- crete," Art. 52. Modulus of Rupture. Taylor's " Practical Cement Testing," pp. 216, 217, 231-234. * The student should compare tension and transverse tests and ascertain the ratio. CEMENT TESTING COMPRESSIVE STRENGTH. (Neat Cement.) Machine used for Crushing. Per Cent of Water used in Mixing ! 1 unci$ 4 is frequently employed instead of K^SaO?. The latter salt is preferable. THE CHEMICAL ANALYSIS OF CEMENT, ETC. 89 to cool; then dissolve in water. The solution thus ob- tained contains the iron and alumina in the form of sul- phates together with the excess of K 2 SO 4 . To determine the Fe 2 Os, the solution is acidified with H 2 SO 4 , the iron reduced to the ferrous condition, and then titrated with a standardized KMnO 4 solution. The re- duction of the iron may be brought about by one of the three methods described below. Reduction by Means of Zinc. Introduce the solution of iron and alumina from the bisulphate fusion into a 200 c.c. Erlenmeyer flask fitted with a one-hole rubber stopper, carrying an exit tube as shown in the drawing (Fig. 39). Add about 3 grams of pure, finely divided zinc and a few cubic centimeters of concentrated H 2 S0 4 . Tightly stopper the flask and allow the outer end of the exit tube to dip into a beaker of water as illustrated. This serves as a trap. The hydrogen generated by the sul- phuric acid and zinc completely reduces the iron to the ferrous condition and drives all air from the flask. When the zinc is entirely dissolved, filter rapidly through a Gooch crucible and wash the crucible several times with small amounts of water. Remove the stopper and quickly titrate the solution in the filter flask with a standardized solution of KMnO 4 . The number of cubic centimeters of KMnO 4 solution used, multiplied by its Fe 2 3 factor, gives the total weight of Fe 2 O 3 . 9 CEMENT TESTING Reduction with a Jones Reductor. A very convenient, as well as quick, method of reduction is accomplished by the aid of a Jones reductor. This apparatus is a glass tube of the form shown in Fig. 40, and is fitted to a filter flask by a tightly fitting rubber stopper. The reductor is filled as follows: Directly over the stopcock a few glass beads are placed and over these a little glass wool. This is then covered with a layer of sand. The balance of the tube, up to the enlargement at the top, is then filled with pure granulated zinc, after which the apparatus is ready for use. Once filled, it may be used indefinitely with no care save the occasional addition of a little zinc as the column of this metal is reduced by the action of acid. When not in use, the reductor should be tightly stop- pered to prevent evaporation, and under no circumstances, either when in use or not in use, should the surface of the liquid be allowed to recede below the top of the column of zinc. The operation of reduction is as follows: Suction is applied to the filter flask and the stopcock of the reductor is so regulated as to allow the liquid to be slowly drawn through the reductor into the filter flask. At first a little dilute H 2 SO 4 is drawn through the apparatus. The liquid to be reduced, which should contain enough H 2 S04 to have a moderate action on zinc, is then run through, and this is FIG. 40. THE CHEMICAL ANALYSIS OF CEMENT, ETC. QI followed by successive small quantities of water to displace all acid. The reductor is then removed from the flask and the solution in the latter is rapidly titrated to a per- manent pink color by means of standardized KMnO 4 solu- tion. As before mentioned, great care must be exercised during the process of reduction to prevent the surface of the liquid from falling below the top of the column of zinc. Reduction by Means of H 2 S. The solution from the bi- sulphate fusion is placed in a 200 c.c. flask, tightly stoppered with a rubber stopper provided with two tubes through which gas can enter and leave the flask (Fig. 41). The tube through which the gas enters should dip below the surface of the liquid, as is shown in the drawing. The solution is heated to boiling and a current HS of pure H 2 S is passed through until the solution is saturated. The tube through which the gas enters is now connected with a C02 generator, and while the solution in the flask is still boiling C0 2 is passed FIG. 41. through until all H 2 S has been removed - until wet lead acetate paper held near the exit tube is no longer blackened. The solution is then allowed to cool in the atmosphere of CO 2 , after which it is filtered and then titrated with standard KMnO 4 as previously described. A1 2 3 . The total weight of A1 2 3 is simply the difference between the combined weight of Fe 2 3 and A1 2 3 , and Fe 2 3 alone. 92 CEMENT TESTING LIME (CaO). Combine the filtrates B and C from the two precipita- tions of iron and alumina, acidify with HC1 and evaporate to a volume of about 250 c.c. Make alkaline with NH 4 OH and heat to boiling.* While the solution is still boiling, add an excess of a boiling solution of (NH 4 ) 2 C 2 O4. Boil for a moment longer and then allow to stand and settle for 20 minutes, or, better still, over night. Filter and wash thoroughly with hot water containing a little (NH 4 ) 2 C 2 O 4 .t (The nitrate, D, is used for the determination of magnesia, MgO.) Place the filter paper containing the precipitate while still wet in a weighed platinum crucible and heat carefully in the Bunsen flame until the paper is burned. Cover the crucible and ignite for 15 or 20 minutes in a good strong blast, to completely reduce the oxalate to oxide. After ignition quickly transfer the hot crucible to a desiccator, preferably one fitted with a U-tube containing soda lime as shown in Fig. 42. When cool, weigh. The crucible should be reheated, cooled and weighed until the weight is constant. This gives total lime, CaO. * A little A1(OH)3 often separates at this point. This will not happen, however, if the Fe(OH) 3 and A1(OH) 3 precipitates were kept hot while being filtered. If any separates, it should be filtered off, ignited and weighed. f Some chemists prefer to redissolve and reprecipitate the calcium, but this is entirely unnecessary in ordinary analytical work. THE CHEMICAL ANALYSIS OF CEMENT, ETC. 93 MAGNESIA (MgO). To the filtrate D from the calcium oxalate precipitation, add HC1 until acid. Evaporate to a volume of about 75 or 100 c.c. Then add an excess of Na 2 HPO 4 or NaNH 4 HPO4 solution and ammonia in moderate excess. Allow to stand at least 4 hours (better over night).* Filter and wash once or twice with a 2.5 per cent solution of NH 4 OH. Dissolve the precipitate on the paper in a little hot, dilute HNO 3 . Add a few drops of Na 2 HPO 4 solution and then NH 4 OH, drop by drop, until in moderate excess, with constant agitation of the solution. Allow to stand 4 hours, or over night if convenient. Filter and wash with 2.5 per cent NH 4 OH. Reject the filtrate. Transfer the precipitate and paper while still wet to a weighed platinum crucible and heat with a low Bunsen flame to dry and char the paper. Burn the paper at as low a temperature as possible. When entirely burned, ignite the crucible in a weak blast flame, cool and weigh. Repeat until constant weight is obtained. This gives weight of MgO as Mg 2 P 2 7 . This weight, multiplied by the factor 0.3621, gives total magnesia, MgO. SULPHURIC ACID (SO 3 ). Into a porcelain evaporating dish or casserole, weigh out one gram of the finely powdered sample, add dilute HC1 to * It is not necessary to remove ammonium salts before making this first precipitation of magnesia. Large amounts of ammonium salts do, however, greatly retard precipitation. 94 CEMENT TESTING cover the powder and take to dryness on the water bath. (By this treatment all the sulphur which was present in the cement as sulphide will be expelled as H 2 S.) Dissolve the residue in water,* treat with NH 4 OH and (NH 4 ) 2 C03 in excess, filter and wash thoroughly. Concentrate the fil- trate, acidify with HC1, heat to boiling for a moment and precipitate the sulphuric acid as BaS0 4 by adding a boiling solution of BaCl 2 , drop by drop, with constant stirring, until in excess. Allow to stand on the water bath about two hours, filter and wash. Or, if convenient, allow to stand over night at the ordinary temperature before filtering. Transfer the filter and precipitate to a platinum crucible and burn the paper at as low a temperature as possible. Ignite for 10 or 15 minutes with the cover off, cool and weigh as BaSO 4 . The weight of BaSO 4 obtained multiplied by the factor 0.3430 gives weight of sulphuric acid (SO 3 ). TOTAL SULPHUR. For the determination of total sulphur, two methods are available. The first to be described below, the fusion method, is the one reported by the committee on uniform methods of analysis. The alternate method is a very good one and is especially good for the determination of sulphur in cement. * Many chemists filter the solution at this point and precipitate the sul- phuric acid immediately without going through the NH 4 OH and (NH^COa treatment. This procedure seems to be very satisfactory though it is liable to give too high results, inasmuch as the BaSC>4 brings down other substances mechanically. THE CHEMICAL ANALYSIS OF CEMENT, ETC. 95 Fusion Method. About i gram of the powdered sample is weighed out into a large platinum crucible and about 5 or 6 grams of pure dry Na 2 C0 3 (free from sulphur) and 0.3 gram of KNOa are added.* This charge should be intimately mixed by means of a platinum spatula or glass rod, and then fused. In order to protect the contents of the crucible from sulphur in the flame, the crucible should be placed through a hole in a piece of asbestos board held in a slightly inclined position. A good Bunsen burner is sufficient to bring about the fusion. Heat until a quiet fusion is obtained. After cooling, the melt is treated in the crucible with boiling water and the solution poured into a tall beaker. More hot water is added and the whole is agitated until disintegration is complete. The solution is then filtered, the filtrate is acidified with HC1 and diluted to about 250 c.c. It is then heated to boiling and the S0 3 is pre- cipitated as BaS0 4 , by the addition, drop by drop, of a boiling solution of BaCk as previously described in the de- termination of sulphuric acid. The precipitate is filtered, washed, ignited and weighed as described in the same place. The weight of BaSO 4 obtained, multiplied by the factor 0.1374, gives total sulphur. Bromine Method. This method depends upon the oxida- tion of S to 80s by means of Br water. Weigh out i gram * As the reagents here used, Na2COs and KNOs, are liable to contain sulphur, a blank should be run first. Results of subsequent analyses can then be corrected for the amount found. 96 CEMENT TESTING of the sample into a porcelain evaporating dish or casserole and treat with Br water in excess. Allow to digest on the water bath for 10 or 15 minutes, then acidify with HC1 and evaporate to dryness. Moisten the residue with i c.c. of concentrated HC1 and dilute with 200 c.c. of water. This solution is then treated with NH 4 OH and (NH 4 ) 2 CO 3 , etc., as described previously in the determination of sulphuric acid (SO 3 ). This result gives all the sulphur as BaS0 4 ; this figure, multiplied by the factor 0.1374, gives total sulphur. SULPHUR EXISTING IN THE CEMENT AS SULPHIDE. From the weight of BaSO 4 , obtained in the determination of total sulphur, subtract the weight of BaSO 4 obtained in the determination of sulphuric acid (SO 3 ). The dif- ference will represent the sulphur existing in the cement as sulphide, weighed in the form of BaSO 4 . By multiplying this weight by the factor 0.1374 the weight of sulphur (S) existing as sulphide will be ascertained. MOISTURE. If a determination of moisture is desired, it can be made in the following simple manner. Weigh out into a platinum crucible i or 2 grams of the sample and heat for an hour in an air bath maintained at a temperature of 110. The crucible is then cooled in a desiccator and weighed. This procedure should be repeated until the weight is con- THE CHEMICAL ANALYSIS OF CEMENT, ETC. 97 slant. The loss in weight represents moisture in the cement.* ALKALIES. In the analysis of cement, many chemists determine alkalies solely by difference, a procedure which is entirely satisfactory for all ordinary purposes. In accurate work, however, and especially in the analysis of clay, the alkalies must be determined gravimetrically. For this determina- tion the J. Lawrence Smith method alone is satisfactory. About 0.5 gram of the sample is intimately mixed with an equal weight of pure NH 4 C1 and 3 grams of pure CaCO 3 . This mixing is usually done in an agate mortar. The mix- ture is transferred to the crucible and covered with about i gram of pure CaCOs. The J. Lawrence Smith crucible, which was especially designed for this determi- nation, is a long tube-like receptacle with a cap for the open end. When the crucible is filled it is capped and placed in an inclined position in a clay cylinder, as shown in Fig. 43. The outer end of the crucible remains cool and thus prevents loss by volati- lization. Instead of a clay cylinder a piece of asbestos * A rough determination of moisture is sometimes made in testing laboratories, with a 100 or 200 gram sample in a porcelain evaporating dish, the weighings being made with an ordinary scale as described on page n. Such a determination is probably entirely satisfactory for all practical purposes. FIG. 43- 9 8 CEMENT TESTING board with a hole in the center to admit the crucible may be conveniently used by clamping it in a vertical position. An ordinary platinum crucible of 25 or 30 c.c. capacity may be used for this de- termination with equally good results, though it requires a little more care during the process of heating. If an ordinary crucible is employed, it should be fitted into a hole in a piece of asbestos board so that about half or two-thirds of the crucible protrudes below the board (Fig. 44). The crucible should be covered FIG. 44. with a platinum lid. Heat is at first applied by means of a Bunsen burner turned very low, or placed some distance below the crucible. If a regular J. Lawrence Smith crucible is employed, a flat flame should be used. When the odor of ammonia is no longer perceptible, the temperature is gradually raised until the full flame of a strong Bunsen burner is employed. Two burners can be used with the J. Lawrence Smith crucible. This heat is continued for about 40 minutes. After the crucible is cool, the cintered mass is loosened by gently tapping the crucible and is then transferred to a porcelain or platinum dish, and treated with 50-75 c.c. of water. Any of the mass which sticks to the crucible is loosened by digesting with a little water, and washed into the dish. The dish containing the cintered mass and water is THE CHEMICAL ANALYSIS OF CEMENT, ETC. 99 digested on the water bath for 30 minutes and any large particles are broken by means of a glass rod. Water lost by evaporation should be replaced. When disintegration is complete, the solution in the dish is decanted through a filter and the residue washed 3 or 4 times by decantation. The residue is then transferred to the filter and washed until free from chlorides.* The filtrate is then treated with an excess of NH 4 OH and (NH 4 ) 2 CO 3 , heated to boiling, filtered and washed once or twice. Inasmuch as the precipitate probably still con- tains traces of alkalies, it should be dissolved in HC1 and reprecipitated by mean's of NH 4 OH and (NH 4 ) 2 CO 3 in excess. It is now filtered and washed thoroughly. The two filtrates are combined, evaporated to dry ness on the water bath and then gently ignited to expel all ammonium salts. Dissolve the residue in a small amount of water and treat with a little NH 4 OH and (NH 4 ) 2 C 2 O 4 to remove the last traces of Ca. Allow to stand over night; filter and wash, allowing the filtrate and washings to run into a weighed platinum dish or large crucible. Evaporate to dry ness and ignite to expel ammonium salts as before. Allow to cool; moisten with HC1 to change any carbonate into chloride, again evaporate tp dryness and ignite at a low red heat. Cool in a desiccator and weigh. This gives total alkali as chloride. Determination of Potassium (K 2 O). Dissolve the ignited chlorides in a small amount of water and treat with a slight * The residue on the filter should be entirely soluble in HC1. 100 CEMENT TESTING excess of platinum chloride solution. The approximate amount of platinum chloride solution necessary can be easily calculated from the weight of the alkali as chloride determined above. The solution should be so dilute that the precipitate redissolves when heated on the water bath. Allow to evaporate on the water bath until the residue solidifies on cooling. Drench the solidified mass with absolute alcohol or with 80 per cent alcohol, and decant the liquid through a very small filter. Wash by decanta- tion with alcohol of the same strength, being careful to bring as little as possible of the precipitate on the paper. The dish and filter are allowed to dry for a few moments, after which the contents of the dish are transferred to a weighed platinum crucible. Any particles of the K 2 PtCl 6 precipitate still adhering to the dish should now be washed through the filter by means of hot water, the solution being caught in the crucible. The latter is then placed on the water bath for a time and then heated for a few moments in an air bath at 135. The dish should be covered during the first few moments in the air bath to prevent loss due to decrepitation. The crucible is cooled in a desiccator and weighed. The weight of K 2 PtCl 6 thus obtained, multiplied by the factor 0.1937, gives the weight of potassium as K 2 O. Determination of Sodium Oxide (Na 2 O). To calculate the weight of Na 2 0, multiply the weight of K 2 PtCl 6 above found by the factor 0.3067 to find the weight of potassium as KC1. This weight should be subtracted from the total weight of alkalies as chloride previously determined. The THE CHEMICAL ANALYSIS OF CEMENT, ETC. IOI difference, which represents the weight of sodium as Nad, should be multiplied by the factor 0.5303, which gives the weight of sodium as Na 2 O. CARBON DIOXIDE (CO 2 ). The determination of CO 2 may be made by either of two totally different methods, the " indirect " and the " direct," both of which are described below. The " indirect " method has the advantage of being rapid and requires less apparatus. It is not as accurate as the direct method, although for determinations in limestone, marl, or other substances rich in CO 2 , it yields very satis- factory results. This method is far less satisfactory for cement, inasmuch as the percentage of C0 2 therein is very small. The " direct " method is very accurate and especially well adapted to substances containing only small amounts of CO 2 . The apparatus required, although somewhat com- plicated, is easily assimilated and consists only of such pieces as are ordinarily found in a chemical laboratory. INDIRECT METHOD. The principle involved in the " indirect " method is the determination of the loss in weight due to expulsion of the CO 2 . A special form of apparatus is needed for this deter- mination, the Schrotter apparatus,* shown in Fig. 45, being one of the more common forms. * Many other forms of apparatus have been described for this de- termination, among them those of Bunsen, Fresenius, Mohr, Geissler, IO2 CEMENT TESTING FIG. 45- Procedure. The apparatus is first cleaned and dried. Compartment b is then about one-third filled with concen- trated H 2 S04 and compartment c is nearly filled with dilute HC1 (i to 3). The glass stopper is then replaced in c and the end of b is closed by means of a piece of rubber tubing carrying a piece of glass rod in one end. The apparatus is then weighed. The sample is then introduced into the apparatus through #, after which the stopper is quickly replaced and the apparatus is again weighed. The increase in weight is the weight of the sample. The rubber stopper is now removed from the end of b and stopcock d is partially opened to allow the HC1 in c to run slowly down into the flask and come into contact with the sample. The C0 2 is thus liberated and is forced out of the apparatus through b, the concentrated H 2 SO4 in this compartment preventing the escape of moisture. The flow of HC1 is so regulated that the C0 2 bubbles through the H 2 SO4 slowly not faster than two bubbles per second. After decomposition is complete and all HC1 has run from c into the flask, stopcock d is closed and the flask is gradually Rohrbeck, etc. All of these are designed on the same principle as the Schrotter apparatus and all are equally well adapted to the determination of CC>2 in carbonates, etc. THE CHEMICAL ANALYSIS OF CEMENT, ETC. 103 heated until the boiling point is reached, in order to expel any CO 2 remaining in solution. The stopcock d is then quickly opened and the stopper in c is quickly replaced by a one-hole rubber stopper carrying a drying tube filled with soda lime. The end of compart- ment b is now connected with a CaCl 2 tube which in turn is connected with an aspirator and a current of air is slowly drawn through the apparatus to drive out all CO 2 . After several liters of air have been drawn through the apparatus, and the liquid contents of the latter are cool, the glass stopper is again placed in c, and the end of b is again closed by means of the rubber tube and glass rod. The apparatus is now carefully weighed. The loss in weight represents the weight of CO 2 . DIRECT METHOD. In the direct determination of CO 2 , the gas, evolved by the action of acid, is first passed through a number of drying tubes, after which it is absorbed in soda lime or a concen- trated solution of KOH. By weighing the absorption tubes before and after the experiment, the actual weight of the CO 2 is obtained. The apparatus employed is shown in Fig. 46. The flask b is of about 100 c.c. capacity and is used for the decompo- sition of the sample. The U-tube c contains a few glass beads moistened with a little concentrated H 2 SO 4 .* The * A small condenser can be advantageously employed between b and c, so arranged as to cause moisture condensed to run back into b. IO4 CEMENT TESTING first half of d is filled with CaCk and the second half with anhydrous CuSO 4 and glass wool or pumice, e contains CaCl 2 to remove final traces of moisture. Glass stoppered U-tubes / and g are the absorption tubes. The former is THE CHEMICAL ANALYSIS OF CEMENT, ETC. 105 filled with soda lime and the latter contains soda lime in the first half and CaCl 2 in the other half. This CaCl 2 absorbs any moisture liberated by the absorption of CO 2 in the soda lime, h is a Liebig bulb filled with concentrated H 2 SO 4 . This prevents moisture from backing up into the absorption tubes, and also indicates the rate at which the gas is passing through the apparatus. The bulb h is connected directly to the aspirator. The small U-tube a is filled with soda lime, and is attached as shown in the figure while air is being drawn through the apparatus, thus freeing it from CO 2 . After filling the various tubes as described above, they are joined together as shown in the drawing, by means of small pieces of rubber tubing. Every joint should be securely wired. Procedure. Air is first passed through the apparatus for some time in order to free it from traces of CO 2 . During this process h may be connected directly to e, as it is not necessary for the absorption tubes to be in position. The weighed sample is then introduced into the flask b, which is immediately closed. The tube a is now removed and the funnel tube in b is filled with dilute HC1 (about 1:3). The two absorption tubes, which should be tightly closed, are now weighed, after which they are connected with the apparatus, as shown, and the joints tightly wired. The dilute HC1 in the funnel tube is now allowed to run into b a little at a time, to decompose the carbonate. The rate of flow must be so regulated that not more than two bubbles a second pass through h. When all HC1 has run 106 CEMENT TESTING into b, the stopcock in the funnel tube is closed and the contents of the flask are gradually heated to the boiling point to drive out any CO2 in solution in the acid. The flame is then removed, the stopcock in the funnel tube is opened and the U-tube a connected as shown in the draw- ing. By means of the aspirator, air is now drawn through the apparatus to completely sweep all CO 2 into the absorp- tion tubes. After several liters of air have been aspirated through the apparatus, the stoppers in / and g are tightly closed, after which they are taken from the apparatus and weighed. The increase in weight is the weight of the CC>2. ANALYSIS or LIMESTONE. Limestone is essentially a carbonate of calcium, but it always contains more or less silica, iron, alumina, and magnesia as impurities. Limestone is very readily at- tacked by dilute HC1, hence no preliminary treatment is necessary to prepare it for the various determinations. Procedure. Weigh out 0.5 gram of the finely powdered sample into a good- sized platinum dish and add water to cover the powder. Add dilute HC1, a little at a time, being careful to cover the dish quickly with a watch glass after each addition. When sufficient acid has been added and effervescence no longer takes place, wash the cover glass, allowing the washings to run into the dish, place the latter on the water bath and evaporate to dryness. Take up with HC1 and water, etc., and proceed with the THE CHEMICAL ANALYSIS OF CEMENT, ETC. 107 various determinations as heretofore described under the heading, " Analysis of Cement." Moisture, loss on ignition, and C0 2 are made with sepa- rate samples. Frequently CO 2 is determined by difference a method which yields results entirely satisfactory for all ordinary purposes. Determinations of SO 3 , total S, and alkalies are not necessary. ANALYSIS or MARL. In the analysis of marl, decomposition is effected by means of HC1 as described under the heading, " Analysis of Limestone." Marl may, however, contain more or less clay which is not decomposed by the acid. If this is the case, as can readily be told from the appearance of the silica, the latter must be fused with dry Na 2 CO 3 , as de- scribed under the heading, " Analysis of Clay." In the analysis of marl the same determinations should be made as in the case of cement the analysis should always include determinations of S, SO 3 and alkalies. ANALYSIS or SLAG. In the analysis of slag, proceed exactly as in the case of cement, making all the determinations as described under the heading, " Analysis of Cement." ANALYSIS OF CLAY. In the analysis of clay, practically the same determina- tions are made as in the case of cement, although a far 108 CEMENT TESTING different preliminary treatment is necessary on account of the insolubility of clay in HC1. This preliminary treat- ment consists in fusing the clay with Na 2 CO3, thereby changing its ingredients into forms which are readily de- composed by HC1. About 0.5 gram of the finely powdered sample* is weighed out into a platinum crucible of 25 or 30 c.c. capacity, 3 or 4 grams of pure dry Na 2 CO 3 are added, and the whole is intimately mixed by stirring with a platinum spatula or glass rod. A little Na 2 CO 3 is now sprinkled on top, the crucible covered, placed on a triangle and heated. Heat should be applied gently at first by means of a Bunsen burner turned low. The temperature is then gradually raised until the full force of a Teclu burner or blast lamp is used. The heating is continued until CO 2 is no longer evolved, and the contents of the dish are in a state of quiet fusion. When the crucible is cool it is placed in a beaker and partially covered with water. It is then allowed to digest until the melt is thoroughly disintegrated. The crucible is then withdrawn and washed with water and a little dilute HC1, the washings being added to the contents of the beaker. The beaker is then covered with a watch glass and HC1 is added a little at a time, the watch glass being quickly replaced after each addition of acid. When C0 2 is no * It is customary to dry the sample at 105 or 110 in the air bath before making the analysis. THE CHEMICAL ANALYSIS OF CEMENT, ETC. 109 longer evolved, the contents of the beaker are transferred to a platinum dish and evaporated to dryness on the water bath. The various determinations Si0 2 , Fe 2 O 3 , etc., are then made as heretofore described in the analysis of cement. For the determination of alkalies in clay, exactly the same procedure is employed as for the determination of alkalies in cement. APPENDIX STANDARD SPECIFICATIONS AND UNIFORM METHODS OF TESTING AND ANALYSIS FOR PORTLAND CEMENT EMBRACING THE REPORT OF THE COMMITTEE ON STANDARD SPECIFICATIONS FOR CEMENT OF THE AMERICAN SOCIETY FOR TESTING MATERIALS; THE REPORT OF THE COMMITTEE ON UNIFORM TESTS OF CEMENT OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS; AND THE REPORT OF THE COMMITTEE ON UNIFORMITY IN TECHNICAL ANALYSIS FOR LIMESTONES, RAW MIXTURES AND PORTLAND CEMENTS OF THE SOCIETY FOR CHEM- ICAL INDUSTRY (NEW YORK SECTION) (Reprinted by permission) APPENDIX. STANDARD SPECIFICATIONS FOR PORTLAND CEMENT Adopted by the American Society for Testing Materials, August i6th, 1909. GENERAL OBSERVATIONS. These remarks have been prepared with a view of pointing out the pertinent features of the various requirements and the precautions to be observed in the interpretation of the results of the tests. The Committee would suggest that the acceptance or rejection under these specifications be based on tests made by an experienced person having the proper means for making the tests SPECIFIC GRAVITY. Specific gravity is useful in detecting adulteration. The results of tests of specific gravity are not necessarily conclusive as an indi- cation of the quality of a cement, but when in combination with the results of other tests may afford valuable indications. FINENESS. The sieves should be kept thoroughly dry. TIME OF SETTING. Great care should be exercised to maintain the test pieces under as uniform conditions as possible. A sudden change or wide range of temperature in the room in which the tests are made, a very dry or humid atmosphere, and other irregularities vitally affect the rate of setting. CONSTANCY OF VOLUME. The tests for constancy of volume are divided into two classes, the first normal, the second accelerated. The latter should be re- garded as a precautionary test only and not infallible. So many 114 APPENDIX conditions enter into the making and interpreting of it that it should be used with extreme care. In making the pats the greatest care should be exercised to avoid initial strains due to molding or to too rapid drying-out during the first twenty-four hours. The pats should be preserved under the most uniform conditions possible, and rapid changes of temperature should be avoided. The failure to meet the requirements of the accelerated tests need not be sufficient cause for rejection. The cement may, how- ever, be held for twenty-eight days, and a retest made at the end of that period, using a new sample. Failure to meet the requirements at this time should be considered sufficient cause for rejection, although in the present state of our knowledge it cannot be said that such failure necessarily indicates unsoundness, nor can the cement be considered entirely satisfactory simply because it passes the tests. SPECIFICATIONS. GENERAL CONDITIONS. All cement shall be inspected. Cement may be inspected either at the place of manufacture or on the work. In order to allow ample time for inspecting and testing, the cement should be stored in a suitable weather-tight building having the floor properly blocked or raised from the ground. The cement shall be stored in such a manner as to permit easy access for proper inspection and identification of each shipment. Every facility shall be provided by the contractor and a period of at least twelve days allowed for the inspection and necessary tests. Cement shall be delivered in suitable packages with the brand and name of manufacturer plainly marked thereon. A bag of cement shall contain 94 pounds of cement net. Each barrel of Portland cement shall contain 4 bags, and each barrel of natural cement shall contain 3 bags of the above net weight. Cement failing to meet the seven-day requirements may be held awaiting the results of the twenty-eight day tests before rejection. All tests shall be made in accordance with the methods proposed APPENDIX 115 by the Committee on Uniform Tests of Cement of the American Society of Civil Engineers, presented to the Society, January 21, 1903, and amended January 20, 1904, and January 15, 1908, with all subsequent amendments thereto. The acceptance or rejection shall be based on the following re- quirements: PORTLAND CEMENT. DEFINITION. This term is applied to the finely pulverized product resulting from the calcination to incipient fusion of an inti- mate mixture of properly proportioned argillaceous and calcareous materials, and to which no addition greater than 3 per cent has been made subsequent to calcination. SPECIFIC GRAVITY. The specific gravity of cement shall not be less than 3.10. Should the test of cement as received fall below this requirement, a second test may be made upon a sample ignited at a low red heat. The loss in weight of the ignited cement shall not exceed 4 per cent. FINENESS. It shall leave by weight a residue of not more than 8 per cent on the No. 100, and not more than 25 per cent on the No. 200 sieve. TIME OF SETTING. It shall not develop initial set in less than thirty minutes; and must develop hard set in not less than one hour, nor more than ten hours. TENSILE STRENGTH The minimum requirements for tensile strength for briquettes one square inch in cross section shall be as follows and the cement shall show no retrogression in strength within the periods specified : Age. Neat Cement. Strength. 24 hours in moist air 175 Ibs. 7 days (i day in moist air, 6 days in water) 500 Ibs. 28 days (i day in moist air, 27 days in water) 600 Ibs. One Part Cement, Three Parts Standard Ottawa Sand. 7 days (i day in moist air, 6 days in water) 200 Ibs. 28 days (i day in moist air, 27 days in water) 275 Ibs. Il6 APPENDIX CONSTANCY OF VOLUME. Pats of neat cement about three inches in diameter, one-half inch thick at the center, and tapering to a thin edge, shall be kept in moist air for a period of twenty-four hours. (a) A pat is then kept in air at normal temperature and observed at intervals for at least 28 days. (b) Another pat is kept in water maintained as near 70 F. as practicable, and observed at intervals for at least 28 days. (c) A third pat is exposed in any convenient way in an atmos- phere of steam, above boiling water, in a loosely closed vessel for five hours. These pats, to satisfactorily pass the requirements, shall remain firm and hard and show no signs of distortion, checking, cracking, or disintegrating. SULPHURIC Aero AND MAGNESIA. The cement shall not contain more than 1.75 per cent of anhydrous sulphuric acid (SO 3 ), nor more than 4 per cent of magnesia (MgO). REPORT OF COMMITTEE ON UNIFORM TESTS OF CEMENT OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS. Presented at the Annual Meeting, January i8th, ign. Your Committee on Uniform Tests of Cement presents the fol- lowing report: SAMPLING. i. Selection of Sample. The selection of the sample for test- ing is a detail that must be left to the discretion of the engineer; the number and the quantity to be taken from each package will depend largely on the importance of the work, the number of tests to be made and the facilities for making them. 2. The sample shall be a fair average of the contents of the package; it is recommended that, where conditions permit, one bar- rel in every ten be sampled. 3. Samples should be passed through a sieve having twenty APPENDIX 117 meshes per linear inch, in order to break up lumps and remove for- eign material; this is also a very effective method for mixing them together in order to obtain an average. For determining the char- acteristics of a shipment of cement, the individual samples may be mixed and the average tested; where time will permit, however, it is recommended that they be tested separately. 4. Method of Sampling. Cement in barrels should be sampled through a hole made in the center of one of the staves, midway between the heads, or in the head, by means of an auger or a sampling iron similar to that used by sugar inspectors. If in bags, it should be taken from surface to center CHEMICAL ANALYSIS. 5. Significance. Chemical analysis may render valuable service in the detection of adulteration of cement with considerable amounts of inert material, such as slag or ground limestone. It is of use, also, in determining whether certain constituents, believed to be harmful when in excess of a certain percentage, as magnesia and sulphuric anhydride, are present in inadmissible proportions. 6. The determination of the principal constituents of cement silica, alumina, iron oxide and lime is not conclusive as an in- dication of quality. Faulty character of cement results more fre- quently from imperfect preparation of the raw material or defective burning than from incorrect proportions of the constituents. Cement made from very finely-ground material, and thoroughly burned, may contain much more lime than the amount usually present, and still be perfectly sound. On the other hand, cements low in lime may, on account of careless preparation of the raw material, be of danger- ous character. Further, the ash of the fuel used in burning may so greatly modify the composition of the product as largely to de- stroy the significance of the results of analysis. 7. Method. As a method to be followed for the analysis of cement, that proposed by the Committee on Uniformity in the Analysis of Materials for the Portland Cement Industry, of the New York Section of the Society for Chemical Industry, and pub- lished in Engineering News, Vol. 50, p. 60, 1903; and in The Engineer- ing Record, Vol. 48, p. 49, 1903, is recommended. n8 APPENDIX SPECIFIC GRAVITY. 8. Significance. The specific gravity of cement is lowered by adulteration and hydration, but the adulteration must be in con- siderable quantity to affect the results appreciably. 9. Inasmuch as the differences in specific gravity are usually very small, great care must be exercised in making the determina- tion. 10. Apparatus and Methqd. The determination of specific gravity is most conveniently 'made with Le Chatelier's apparatus. I FIG. i. This consists of a flask (D), Fig. i, of 120 cu. cm. (7.32 cu. in.) capacity, the neck of which is about 20 cm. (7.87 in.) long; in the middle of this neck is a bulb (C), above and below which are two marks (F) and (); the volume between these marks is 20 cu. cm. (1.22 cu. in.). The neck has a diameter of about 9 mm. (0.35 in.), and is graduated into tenths of cubic centimeters above the mark (F). 11. Benzine (62 Baume naphtha), or kerosene free from water, should be used in making the determination. 12. The specific gravity is determined as follows: The flask is filled with either of these liquids to the lower mark (), and 64 gms. (2.25 oz.) of powder, cooled to the temperature of APPENDIX IIQ the liquid, is gradually introduced through the funnel (B) [the stem of which extends into the flask at the top of the bulb (C)], until all the powder is introduced, and the level of the liquid rises to some division of the graduated neck. This reading plus 20 cu. cm. is the volume displaced by 64 gms. of the powder. 13. The specific gravity is then obtained from the formula: Weight of Cement, in grams Specific Gravity = Displaced Volume, in cubic centimeters 14. The flask, during the operation, is kept immersed in water in a jar (^4), in order to avoid variations in the temperature of the liquid. The results should agree within o.oi. The determination of specific gravity should be made on the cement as received; and, should it fall below 3.10, a second determination should be made on the sample ignited at a low red heat. 15. A convenient method for cleaning the apparatus is as follows: The flask is inverted over a large vessel, preferably a glass jar, and shaken vertically until the liquid starts to flow freely; it is then held still in a vertical position until empty; the remaining traces of cement can be removed in a similar manner by pouring into the flask a small quantity of clean liquid benzine or kerosene and repeating the operation. FINENESS. 16. Significance. It is generally accepted that the coarser particles in cement are practically inert, and it is only the extremely fine powder that possesses adhesive or cementing qualities. The more finely cement is pulverized, all other conditions being the same, the more sand it will carry and produce a mortar of a given strength. 17. The degree of final pulverization which the cement re- ceives at the place of manufacture is ascertained by measuring the residue retained on certain sieves. Those known as the No. 100 and No. 200 sieves are recommended for this purpose. 18. Apparatus. The sieves should be circular, about 20 cm. (7.87 in.) in diameter, 6 cm. (2.36 in.) high, and provided with a pan, 5 cm. (1.97 in.) deep, and a cover. 120 APPENDIX 19. The wire cloth should be of brass wire having the following diameters: No. 100, 0.0045 m -5 No. 200, 0.0024 in. 20. This cloth should be mounted on the frames without dis- tortion; the mesh should be regular in spacing and be within the following limits: No. 100, 96 to 100 meshes to the linear inch. No. 200, 188 to 200 meshes to the linear inch. 21. Fifty grams (1.76 oz.) or 100 g. (3.52 oz.) should be used for the test, and dried at a temperature of 100 Cent. (2i2Fahr.) prior to sieving, tj 22. Method. The thoroughly dried and coarsely screened sample is weighed and placed on the No. 200 sieve, which, with pan and cover attached, is held in one hand in a slightly inclined posi- tion, and moved forward and backward, at the same time striking the side gently with the palm of the other hand, at the rate of about 200 strokes per minute. The operation is continued until not more than one-tenth of i per cent passes through after one minute of con- tinuous sieving. The residue is weighed, then placed on the No. 100 sieve and the operation repeated. The work may be expedited by placing in the sieve a small quantity of large steel shot. The results should be reported to the nearest tenth of i per cent. NORMAL CONSISTENCY. 23. Significance. The use of a proper percentage of water in making the pastes * from which pats, tests of setting, and briquettes are made, is exceedingly important, and affects vitally the results obtained. 24. The determination consists in measuring the amount of water required to reduce the cement to a given state of plasticity, or to what is usually, designated the normal consistency. 25. The Committee recommends the following method for determining normal consistency. *The term "paste" is used in this report to designate a mixture of cement and water, and the word "mortar" a mixture of cement, sand and water. APPENDIX 121 26. Method, Vicat Needle Apparatus. This consists of a frame (1C), Fig. 2, bearing a movable rod (,), with the cap (A) at one end, and at the other the cylinder (B), i cm. (0.39 in.) in diam- eter, the cap, rod, and cylinder weighing 300 gms. (10.58 oz.). The rod, which can be held in any desired position by a screw (F), car- ries an indicator, which moves over a scale (graduated to centi- meters) attached to the frame (K). The paste is held by a conical, hard-rubber ring (7), 7 cm. (2.76 in.) in diameter at the base, 4 cm. (1.57 in.) high, resting on a glass plate (7), about 10 cm. (3.94 in.) square. D D ma A VICAT NEEDLE. FlG. 2. 27. In making the determination, the same quantity of cement as will be subsequently used for each batch in making the briquettes, but not less than 500 gms., is kneaded into a paste, as described in Paragraph 52, and quickly formed into a ball with the hands, com- pleting the operation by tossing it six times from one hand to the other, maintained 6 in. apart; the ball is then pressed into the rubber ring, through the larger opening, smoothed off, and placed (on its large end) on a glass plate and the smaller end smoothed off with a trowel; the paste, confined in the ring, resting on the plate, is placed under the rod bearing the cylinder, which is brought in con- tact with the surface and quickly released. 122 APPENDIX 28. The paste is of normal consistency when the cylinder in one minute from the time it is released penetrates to a point in the mass 10 mm. (0.39 in.) below the top of the ring. Great care must be taken to fill the ring exactly to the top. The apparatus must be free from all vibrations during the test. 29. The trial pastes are made with varying percentages of water until the correct consistency is obtained. 30. The Committee has recommended, as normal, a paste, the consistency of which is rather wet, because it believes that variations in the amount of compression to which the briquette is subjected in moulding are likely to be less with such a paste. 31. Having determined in this manner the proper percentage of water required to produce a paste of normal consistency, the proper percentage required for the mortars is obtained from the table below. PERCENTAGE OF WATER FOR STANDARD MORTARS One cement, One cement, One cement, Neat. three standard Neat. three standard Neat. three standard Ottawa sand. Ottawa sand. Ottawa sand. is 8.0 23 9-3 31 10.7 16 8.2 24 9-5 32 10.8 17 8.3 25 9-7 33 II .0 18 8.5 26 9.8 34 II .2 iQ 8.7 27 10. O 35 "5 20 8.8 28 10. 2 36 n-5 21 9.0 29 10.3 37 ii. 7 22 9.2 30 io-5 38 ii. 8 TIME OF SETTING. 32. Significance. The object of this test is to determine the time which elapses from the moment water is added until the paste ceases to be fluid and plastic (called the "initial set"), and also the time required for it to acquire a certain degree of hardness (called the "final" or "hard set"). The former of these is the more im- portant, since, with the commencement of setting, the process of crystallization or hardening is said to begin. As a disturbance of this process may produce a loss of strength, it is desirable to com- APPENDIX 123 plete the operation of mixing and moulding or incorporating the mortar into the work before the cement begins to set. 33. It is usual to measure arbitrarily the beginning and end of the setting by the penetration of weighted wires of given di- ameters. 34. Method. For this purpose the Vicat Needle, which has already been described in Paragraph 26, should be used. 35. In making the test, a paste of normal consistency is molded and placed under the rod (Z,), Fig. 2, as described in Para- graph 27; this rod, bearing the cap (D) at one end and the needle (H), i mm. (0.039 m O m diameter, at the other, weighing 300 gms. (10.58 oz.). The needle is then carefully brought in contact with the surface of the paste and quickly released. 36. The setting is said to have commenced when the needle ceases to pass a point 5 mm. (0.20 in.) above the upper surface of the glass plate, and is said to have terminated the moment the needle does not sink visibly into the mass. 37. The test pieces should be stored in moist air during the test; this is accomplished by placing them on a rack over water con- tained in a pan and covered with a damp cloth, the cloth to be kept away from them by means of a wire screen; or they may be stored in a moist box or closet. 38. Care should be taken to keep the needle clean, as the collec- tion of cement on the sides of the needle retards the penetration, while cement on the point reduces the area and tends to increase the penetration. 39. The determination of the time of setting is only approxi- mate, being materially affected by the temperature of the mixing water, the temperature and humidity of the air during the test, the percentage of water used, and the amount of kneading the paste receives. STANDARD SAND. 40. The Committee recommends the natural sand from Ottawa, 111., screened to pass a sieve having 20 meshes per linear inch and retained on a sieve having 30 meshes per linear inch; the wires to have diameters of 0.0165 and 0.0112 in., respectively, i.e., half the width of the opening in each case. Sand having passed the No. 20 124 APPENDIX sieve shall be considered standard when not more than i per cent passes a No. 30 sieve after one minute's continuous sifting of a 5oo-g sample.* FORM OF TEST PIECES. 41. For tension tests the Committee recommends the form of test piece shown in Fig. 3. DETAILS FOR BRIQUETTE. FlG. 3. 42. For compression tests a 2-in. cube is recommended. MOLDS. 43. The molds should be made of brass, bronze, or some equally non-corrodible material, having sufficient metal in the sides to pre- vent spreading during molding. 44. Gang molds, which permit molding a number of briquettes at one time, are preferred by many to single molds; since the *This sand may be obtained from the Ottawa Silica Company at a cost of two cents per pound, f. o. b. cars, Ottawa, Illinois. APPENDIX 125 greater quantity of mortar that can be mixed tends to produce greater uniformity in the results. The type shown in Fig. 4 is recommended. DETAILS FOR GANG MOULD. FIG. 4. 45. The molds should be wiped with an oily cloth before using. MIXING. 46. All proportions should be stated by weight; the quantity of water to be used should be stated as a percentage of the dry material. 47. The metric system is recommended because of the con- venient relation of the gram and the cubic centimeter. 48. The temperature of the room and the mixing water should be as near 21 Cent. (70 Fahr.) as it is practicable to maintain it. 49. The sand and cement should be thoroughly mixed dry. The mixing should be done on some non-absorbing surface, prefer- ably plate glass. If the mixing must be done on an absorbing sur- face it should be thoroughly dampened prior to use. 50. The quantity of material to be mixed at one time de- pends on the number of test pieces to be made; about 1,000 gms. (35.28oz.) makes a convenient quantity to mix, especially by hand methods. 51. The Committee, after investigation of the various mechan- ical mixing machines, has decided not to recommend any machine that has thus far been devised, for the following reasons: (i) The tendency of most cement is to "ball up" in the machine^ thereby preventing the working of it into a homogeneous paste; (2) there is no means of ascertaining when the mixing is complete without stopping the machine; and (3) the difficulty of keeping the machine clean. 52. Method. The material is weighed and placed on the mix- ing table, and a crater formed in the center, into which the proper percentage of clean water is poured; the material on the outer edge 126 APPENDIX is turned into the crater by the aid of a trowel. As soon as the water has been absorbed, which should not require more than one minute, the operation is completed by vigorously kneading with the hands for an additional one minute, the process being similar to that used in kneading dough. A sand-glass affords a convenient guide for the time of kneading. During the operation of mixing, the hands should be protected by gloves, preferably of rubber. MOLDING. 53. Having worked the paste or mortar to the proper consist- ency, it is at once placed in the molds by hand. 54. The Committee has been unable to secure satisfactory re- sults with the present molding machines; the operation of machine moulding is very slow, and the present types permit of molding but one briquette at a time, and are not practicable with the pastes or mortars herein recommended. 55. Method. The molds should be filled immediately after the mixing is completed, the material pressed in firmly with the fingers and smoothed off with a trowel without mechanical ramming; the material should be heaped up on the upper surface of the mold, and, in smoothing off, the trowel should be drawn over the mold in such a manner as to exert a moderate pressure on the excess material. The mold should be turned over and the operation repeated. 56. A check upon the uniformity of the mixing and molding is afforded by weighing the briquettes just prior to immersion, or upon removal from the moist closet. Briquettes which vary in weight more than 3 per cent from the average should not be tested. STORAGE or THE TEST PIECES. 57. During the first 24 hours after molding, the test pieces should be kept in moist air to prevent them from drying out. 58. A moist closet or chamber is so easily devised that the use of the damp cloth should be abandoned. Covering the test pieces with a damp cloth is objectionable, as commonly used, because the cloth may dry out unequally, and, in consequence, the test pieces are not all maintained under the same condition. Where a moist closet APPENDIX 127 is not available, a cloth may be used and kept uniformly wet by immersing the ends in water. It should be kept from direct contact with the test pieces by means of a wire screen or some similar arrangement. 59. A moist closet consists of a soapstone or slate box, or a metal-lined wooden box the metal lining being covered with felt and this felt kept wet. The bottom of the box is so constructed as to hold water, and the sides are provided with cleats for holding glass shelves on which to place the briquettes. Care should be taken to keep the air in the closet uniformly moist. 60. After 24 hours in moist air, the test pieces for longer periods of time should be immersed in water maintained as near 21 Cent. (70 Fahr.) as practicable; they may be stored in tanks or pans, which should be of non-corrodible material. TENSILE STRENGTH. 61. The tests may be made on any machine. A solid metal clip, as shown in Fig. 5, is recommended. This clip is to be used without cushioning at the points of contact with the test specimen. The bearing at each point of contact should be | in. wide and the distance between the center of contact on the same clip should be i^ in. 62. Test pieces should be broken as soon as they are removed from the water. Care should be observed in centering the briquettes in the testing machine, as cross-strains, produced by improper centering, tend to lower the breaking strength. The load should not be applied too suddenly, as it may produce vibration, the shock from which often breaks the briquettes before the ultimate strength is reached. Care must be taken that the clips and the sides of the briquette be clean and free from grains of sand or dirt, which would prevent a good bearing. The load should be applied at the rate of 600 Ib. per min. The average of the bri- quettes of each sample tested should be taken as the test, excluding any results which are manifestly faulty. 3 FORM OF CLIR FIG. 5. 128 APPENDIX CONSTANCY OF VOLUME. 63. Significance. The object is to develop those qualities which tend to destroy the strength and durability of a cement. As it is highly essential to determine such qualities at once, tests of this character are for the most part made in a very short time, and are known, therefore, as accelerated tests. Failure is revealed by crack- ing, checking, swelling, or disintegration, or all of these phenomena. A cement which remains perfectly sound is said to be of constant volume. 64. Methods. Tests for constancy of volume are divided into two classes: (i) normal tests, or those made in either air or water maintained at about 21 Cent. (70 Fahr.), and (2) accelerated tests, or those made in air, steam, or water at a temperature of 45 Cent. (113 Fahr.) and upward. The test pieces should be allowed to remain 24 hours in moist air before immersion in water or steam, or preservation in air. 65. For these tests, pats, about 7^ cm. (2.95 in.) in diameter, i cm. (0.49 in.) thick at the center, and tapering to a thin edge, should be made, upon a clean glass plate [about 10 cm. (3.94 in.) square], from cement paste of normal consistency. 66. Normal Test. A pat is immersed in water maintained as near 21 Cent. (70 Fahr.) as possible for 28 days, and observed at intervals. A similar pat, after 24 hours in moist air, is maintained in air at ordinary temperature and observed at intervals. 67. Accelerated Tests. A pat is placed in an atmosphere of steam upon a wire screen i in. above boiling water for five (5) hours. The apparatus should be so constructed as to permit the free escape of steam and maintain atmospheric pressure. Since the type of apparatus used has a great influence on the uniformity of the results, that shown in Fig. 8 is recommended. 68. To pass these tests satisfactorily, the pats should remain firm and hard, and show no signs of cracking, distortion or disintegration. 69. Should the pat leave the plate, distortion may be detected best with a straight-edge applied to the surface which was in contact with the plate. 70. In the present state of our knowledge it cannot be said that cement should necessarily be condemmed simply for failure to APPENDIX 129 330 APPENDIX pass the accelerated tests; nor can a cement be considered entirely satisfactory simply because it has passed these tests. Submitted on behalf of the Committee, GEORGE S. WEBSTER, Chairman. RICHARD L. HUMPHREY, Secretary. JANUARY iSxn, 1911. Committee. GEORGE S. WEBSTER, RICHARD L. HUMPHREY, GEORGE F. SWAIN, ALFRED NOBLE, Louis C. SABIN, S. B. NEWBERRY, CLIFFORD RICHARDSON, W. B. W. HOWE, F. H. LEWIS. NEW YORK SECTION SOCIETY FOR CHEMICAL INDUSTRY Method Suggested for the Analysis of Limestones, Raw Mixtures and Portland Cements by the Committee on Uniformity in Techni- cal Analysis with the Advice of W. F. Hillebrand. SOLUTION. One-half gram of the finely-powdered substance is to be weighed out and, if a limestone or unburned mixture, strongly ignited in a covered platinum crucible over a strong blast for fifteen minutes, or longer if the blast is not powerful enough to effect complete conver- sion to a cement in this time. It is then transferred to an evaporating dish, preferably a platinum for the sake of celerity in evapora- tion, moistened with enough water to prevent lumping, and 5 to 10 c.c. of strong HC1 added and digested with the aid of gentle heat and agitation until solution is complete. Solution may be aided by APPENDIX 131 light pressure with the flattened end of a glass rod.* The solution is then evaporated to dryness, as far as this may be possible on the bath. SILICA (SiO 2 ). The residue without further heating is treated at first with 5 to 10 c.c. of strong HC1, which is then diluted to half strength or less, or upon the residue may be poured at once a larger volume of acid of half strength. The dish is then covered and digestion allowed to go on for 10 minutes on the bath, after which the solution is filtered and the separated silica washed thoroughly with water. The filtrate is again evaporated to dryness, the residue without further heating taken up with acid and water and the small amount of silica it con- tains separated on another filter paper. The papers containing the residue are transferred wet to a weighed platinum crucible, dried, ignited, first over a Bunsen burner until the carbon of the filter is completely consumed, and finally over the blast for 15 minutes and checked by a further blasting for 10 minutes or to constant weight. The silica, if great accuracy is desired, is treated in the crucible with about 10 c.c. of HF and four drops of H 2 SO 4 and evaporated over a low flame to complete dryness. The small residue is finally blasted, for a minute or two, cooled and weighed. The difference between this weight and the weight previously obtained gives the amount of silica.f ALUMINA AND IRON (A1 2 O 3 AND Fe 2 O 3 ). The filtrate, about 250 c.c., from the second evaporation for Si0 2 , is made alkaline with NH 4 OH after adding HC1, if need be, to insure a total of 10 to 15 c.c. strong acid, and boiled to expel excess of NH 3 , or until there is but a faint odor of it, and the pre- cipitated iron and aluminum hydrates, after settling, are washed once by decantatkm and slightly on the filter. Setting aside the filtrate, * If anything remains undecomposed it should be separated, fused with a little Na 2 CO 3 , dissolved and added to the original solution. Of course a small amount of separated non-gelatinous silica is not to be mistaken for undecomposed matter. t For ordinary control in the plant laboratory this correction may, perhaps, be neglected; the double evaporation never. 132 APPENDIX the precipitate is dissolved in hot dilute HC1, the solution passing into the beaker in which the precipitation was made. The-aluminum and iron are then reprecipitated by NH 4 OH, boiled and the second precipitate collected and washed on the same filter used in the first instance. The filter paper, with the precipitate, is then placed in a weighed platinum crucible, the paper burned off and the precipitate ignited and finally blasted 5 minutes, with care to prevent reduction, cooled and weighed as A1 2 C>3 + Fe 2 C>3.* IRON (Fe 2 3 ). The combined iron and aluminum oxides are fused in a platinum crucible at a very low temperature with about 3 to 4 grams of KHSO 4 , or, better, NaHSO 4 , the melt taken up with so much dilute H 2 SO 4 that there shall be no less than 5 grams absolute acid and enough water to effect solution on heating. The solution is then evaporated and eventually heated till acid fumes come off copiously. After cooling and redissolving in water the small amount of silica is filtered out, weighed and corrected by HF and H 2 SO 4 .f The filtrate is reduced by zinc, or preferably by hydrogen sulphide, boiling out the excess of the latter afterwards while passing CO 2 through the flask, and titrated with permanganate. J The strength of the per- manganate solution should not be greater than .0040 grm. Fe 2 Os per c.c. LIME (CaO). To the combined filtrate from the A1 2 O 3 -f Fe 2 O 3 precipitate a few drops of NH 4 OH are added, and the solution brought to boil- ing. To the boiling solution 20 c.c. of a saturated solution of ammonium oxalate are added, and the boiling continued until the precipitated CaC 2 O 4 assumes a well-defined granular form. It is then allowed to stand for 20 minutes, or until the precipitate has * This precipitate contains TiO2, P2Os, Mn 3 O4. t This correction of A1 2 O3 Fe2O3 for silica should not be made when the HF correction of the main silica has been omitted, unless that silica was obtained by only one evaporation and filtration. After two evaporations and nitrations i to 2 mg. of SiO2 are still to be found with the A^Os Fe2Oa. | In this way only is the influence of titanium to be avoided and a cor- rect result obtained for iron. APPENDIX 133 settled, and then filtered and washed. The precipitate and filter are placed wet in a platinum crucible, and the paper burned off over a small flame of a Bunsen burner. It is then ignited, redissolved in HC1, and the solution made up to 100 c.c. with water. Ammonia is added in slight excess, and the liquid is boiled. If a small amount of A1 2 O 3 separates, this is filtered out, weighed, and the amount added to that found in the first determination, when greater accu- racy is desired. The lime is then reprecipitated by ammonium oxa- late, allowed to stand until settled, filtered, and washed,* weighed as oxide by ignition and blasted in a covered crucible to constant weight, or determined with dilute standard permanganate.! MAGNESIA (MgO). The combined filtrates from the calcium precipitates are acidi- fied with HC1 and concentrated on the steam bath to about 150 c.c., 10 c.c. of saturated solution of Na(NH 4 )HPO 4 are added, and the solution boiled for several minutes. It is then removed from the flame and cooled by placing the beaker in ice water. After cooling, NH 4 OH is added drop by drop with constant stirring until the crys- talline ammonium-magnesium ortho-phosphate begins to form, and then in moderate excess, the stirring being continued for several minutes. It is then set aside for several hours in a cool atmosphere and filtered. The precipitate is redissolved in hot dilute HC1, the solution made up to about 100 c.c., i c.c. of a saturated solution of Na(NH 4 )HP0 4 added, and ammonia drop by drop, with constant stirring, until the precipitate is again formed as described and the ammonia is in moderate excess. It is then allowed to stand for about 2 hours, when it is filtered on a paper or a Gooch crucible, ignited, cooled and weighed as Mg 2 P2O 7 . ALKALIES (K 2 O AND Na 2 0). For the determination of the alkalies, the well-known method of Prof. J. Lawrence Smith is to be followed, either with or without the addition of CaCO 3 with NI^Cl. * The volume of wash- water should not be too large; vide Hillebrand. t The accuracy of this method admits of criticism, but its convenience and rapidity demand its insertion. 134 APPENDIX ANHYDROUS SULPHURIC ACID (S0 3 ). One gram of the substance is dissolved in 15 c.c. of HC1, filtered and residue washed thoroughly.* The solution is made up, to 250 c.c. in a beaker and boiled. To the boiling solution 10 c.c. of a saturated solution of BaQ 2 is added slowly drop by drop from a pipette and the boiling continued until the precipitate is well formed, or digestion on the steam bath may be substituted for the boiling. It is then set aside over night, or for a few hours, filtered, ignited and weighed as BaS0 4 . TOTAL SULPHUR. One gram of the material is weighed out in a large platinum cru- cible and fused with Na 2 C0 3 and a little KNO 3 , being careful to avoid contamination from sulphur in the gases from source of heat. This may be done by fitting the crucible in a hole in an asbestos board. The melt is treated in the crucible with boiling water and the liquid poured into a tall narrow beaker and more hot water added until the mass is disintegrated. The solution is then filtered. The filtrate contained in a No. 4 beaker is to be acidulated with HC1 and made up to 250 c.c. with distilled water, boiled, the sul- phur precipitated as BaSO 4 and allowed to stand over night or for a few hours. Loss ON IGNITION. Half a gram of cement is to be weighed out in a platinum cru- cible, placed in a hole in an asbestos board so that about | of the crucible projects below, and blasted 15 minutes, preferably with an inclined flame. The loss by weight, which is checked by a second blasting of 5 minutes, is the loss on ignition. May, 1903: Recent investigations have shown that large errors in results are often due to the use of impure distilled water and reagents. The analyst should, therefore, test his distilled water by evaporation and his reagents by appropriate tests before proceeding with his work. * Evaporation to dryness is unnecessary, unless gelatinous silica should have separated, and should never be performed on a bath heated by gas; vide Hillebrand. INDEX. Aging, 33. Alkalies, 4. determination of, 97. Alkali waste, 5. Alumina, 3. determination of, 91. Analyses of cements, typical, 5. chemical, 80. Appendix, in. Beam molds, 43, 78. Beams, breaking of, 44. Boiling test apparatus, 75. Briquette molds, 34, 78. Briquettes, breaking of, 37. mortar, 36. Burette, 78. Lesley, 78. Carbonic acid, 4. Carbon dioxide, direct method for determination of, 103. indirect method for determination of, 101. Cement, chemical analysis of, 84. classification of, i. definition of, i. rock, 5. specific gravity of, 14. typical analyses of, 5. Chalk, 6. Chemical analysis, 80. factors influencing, 82. sample for, 83. Classification of -cements, i. Clay, 5. analysis of, 107. Clips, 70. Composition of cement, i, 33. Compression tool, 70. Compressive strength, 41. determination of, 42. report blanks, 46, 47. Constancy of volume, 28. determination of, 29. report blank, 32. Constant level apparatus, 75. Cube molds, 42, 78. Cubes, breaking of, 43. D Definition of cement, i. Effective size of sand, 52. Fairbanks machine, 63. operation of, 64. Falkenau-Sinclair machine, 64. operation of, 66. Fineness, 9, 34. determination of, n. importance of, 9. report blank, 13. Inspection, 7. Iron and Alumina, determination of, 87. 135 i 3 6 INDEX Iron, determination of, 88. reduction of, by H^S, 91. reduction of, by zinc, 89, 90. Iron oxide, 3. J Jones reductor, 90. Laboratory equipment, 63. Le Chatelier flask, 15. Lesley burette, 78. storage tank, 77. Lime, 3. determination of, 92. Limestone, 6. analysis of, 106. Loam in sand, determination of, 49. Loss on ignition, determination of, 84. M Machines, for compression tests, 72. for tension tests, 63. Magnesia, 4. determination of, 93. Manufacture of cement, 5. Marl, 5. analysis of, 107. Mechanical analysis, of sand, 50. of stone, 54. Mixed cement, 2. Mixing, 21. Modulus of rupture, calculation of, 44- determination of, 43. report blank, 48. Moist closet, 76. Moisture, determination of, 96. Molds, beam, 43, 78. briquette, 34, 78. cube, 42, 78. Mortar briquettes, 36. N Natural cement, i, 4. Normal consistency, 20. determination of, 22. report blank, 26. O Olsen briquette machine, 63, 64. operation of, 66. Olsen hydraulic compression ma- chine, 72. Pats, preparation of, 29. Portland cement, i. Potash, determination of, 99. Pozzuolana cement, 2, 4. R Raw material, 5. Riehle machine, 63, 64. operation of, 66. Sampling, 7, 83. auger, 8. Sand, 49. determination of loam in, 49. mechanical analysis of, 50. report blank, 60. percentage of loam report blank, 59- sifter, 74. specific gravity of, report blank, 61. standard, 49. weight per cubic foot of, report blank, 61. Scales, n, 75. Set, time of, 23. Shot machines, 63. Sieves, 10. INDEX 137 Sifter, sand, 74. Silica, 3. determination of, 85. Slag, analysis of, 107. Soda, determination of, 100. Specific gravity of cement, 14. determination of, 16. report blank, 19. significance of, 14. Standard specifications, in. Stone, 54. mechanical analysis of, 54. specific gravity of, 55. report blank, 61. weight per cubic foot of, report ' blank, 62. Storage, 7. tanks, 76. Lesley, 77. Sulphur, 4. as sulphide, 96. determination of, 94. Sulphuric acid, 4. determination of, 93. Sulphur trioxide, 4. Table, 77. Tensile strength, 33. determination of, mortar, 36. determination of, neat cement, 34. Tensile strength, factors affecting. 33- report blanks, 39, 40. Testing machines, 63. Tests, accelerated, 29. normal, 28. transverse, 43. Time of set, 23. determination of, 24. factors affecting, 24. report blank, 27. significance of, 23. Tool, compression, 70. Transverse test attachment, 70. U Uniformity coefficient, 52. Universal testing machine, 72. Unsoundness, causes of, 28. Vicat apparatus, 20. Voids in sand, 52. determination of, 52. Voids in stone, 55. determination of, 56, 57. W Weight per cubic foot of sand, 54. of stone, 56. Work table, 77. D. VAN NOSTRAND COMPANY 25 PARK PLACE NEW YORK SHORT-TITLE CATALOG OF JtaMkathms OP SCIENTIFIC AND ENGINEERING BOOKS This list includes the technical publications of the following English publishers : SCOTT, GREENWOOD & CO. CROSBY LOCKWOOD & SON CONSTABLE & COMPANY, Ltd. TECHNICAL PUBLISHING CO. ELECTRICIAN PRINTING & PUBLISHING CO., for whom D. Van Nostrand Company are American agents. Descriptive Circulars sent on request. JULY, 1912 SHORT-TITLE CATALOG OF THE Publications and Importations D. 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