|RESULTS OF TESTs MADE IN THE COLLECTIVE PORTLAND CEMENT EXHIBIT AND MODEL TESTING LABORATORY OF THE ASSOCIATION OF AMERICAN PORTLAND CEMENT MANUFACTURERS. ; : : LOUISIANA PURCHASE EXPOSITION St. Louis, Mo : i. ; º .****** ** a sº * f. 3. *. w : a- ~$. X-> III.7.2 ºf Tāº; tº \ jLilliſtill |U ~. jº - - : * ~ * * ** . tº FIU#5ušUSüe - s sº º , ***. T ; : | #§ ; § i Results of tests º - MADE IN THE COLLECTIVE PORTLAND CEMENT EXHIIBIT AND MODEL TESTING LABORATORY OF THE ASSOCIATION OF AMERICAN PORTLAND CEMENT MANUFACTURERS. : : ; ; ; ; ; ; ; ; RICHARD L. HUMPHREY, M. Am. Soc. C. E. [IN CHARGE] LOUISIANA PURCHASE EXPOSITION ST. LOUIS, MO. IOO4. - 2- º --- º -- --- - - - - | || || || --- ASSOC I ATION OF PORTLAND CEMENT MANU-ACTURERS ---------------------------------- - ------------------------ º- º The Association of American Portland Cement Manufacturers was awarded two Grand Prizes, one for the collective exhibit and another for the model testing laboratory. The Collective Portland Cement Exhibit and Model Testing Laboratory of the Associa- tion of American Portland Cement Manufacturers, and the Results of Tests at the Louisiana Purchase Exposition, St. Louis, Mo.” RICHARD L. HUMPHREY, M. AM. Soc. C. E. [IN CHARGE. Great expositions mark the progress made in the industrial world, and emphasize the advance in particular lines. The Louis- iana Purchase Exposition was no exception. Those who were fortunate in being able to attend the Exposition at Chicago in 1893 and St. Louis in Igo4 doubtless observed the progress which had been made in the branches in which they were especially interested. To those interested in cement, a very noticeable feature of the former was the absence of an American Portland Cement Exhibit, and the elaborate German exhibits of this material. This was naturally to be expected at a period when American Portland cement was hardly known and was regarded as of doubtful quality, while German Portland cement was universally used and was held in very high regard. The total consumption of Portland cement in 1903 was 3,264,80I barrels, of which 82 per cent. was of foreign and only 18 per cent. of domestic manufacture. In the decade which has since elapsed a great change has taken place in the production and consumption of American Portland cement. The production has increased 450 per cent., while the importations have fallen off about 73 per cent.; the consumption now exceeds 26,505,881 barrels, and this country has grown from one of the smallest to one of the largest Portland cement producing coun- tries of the world. * Presented jointly to the Association of American Portland Cement Manu- facturers and the American Society for Testing Materials Reprinted from the copy- +ighted proceedings. ^: - s: **** ºx f } 4.55% §2. — , , ºp. < * * * ~ * 4 It was quite appropriate that this remarkable growth of the cement industry in America should be fittingly exploited at St. Louis, and it was natural that this exploitation should be made by the American Portland cement manufacturers in a collective exhibit. Such an exhibit formed the gateway to the mining gulch of the Exposition and was one of the most attractive of the outside individual exhibits. The fact that there were no foreign cement exhibits worthy of note, served to emphasize the withdrawal of the foreign Portland cement from the American market, resulting Tºº- - - - - FIG. I.-General View of Building. from the development of the American Portland cement industry. In yet another particular was this collective exhibit noticeable. In 1893 the American Portland cement manufacturer, while not openly hostile to the inspection and testing of his product, was nevertheless not a strong advocate and frequently rebelled against the restrictions placed on him by the testing engineer. Yet it was because of this continual raising of requirements which com- pelled the manufacturer to improve his product, that he occupies a premier position in the cement industry to-day. We now find the manufacturer no longer the opponent but the firm advocate of 5 proper methods for testing. This new attitude was shown in the equipment and operation of the Model Testing Laboratory in which was exploited the methods for testing cement proposed by the special committee of the American Society of Civil Engineers, whose report was distributed gratuitously. Only those who have had an active part in the erection of buildings and installation of exhibits at a great exposition can appreciate the vexatious delays occasioned by unforeseen difficulties; this was particularly true of the cement exhibit. FIG. 2–Ceneral View of Laboratory. It was originally intended that the work of construction should be carried on during the Exposition as a working exhibit. To secure greater advantages in an educational way it was subse- quently decided to complete it as soon as possible, but before this could be accomplished the Exposition was well towards its close. The buildings, and the installation of the equipment of the labora- tory and of the other exhibits were quickly completed and the whole placed in a working condition. () The completed Exhibit formed a comprehensive exposition of the Portland Cement Industry, comprising: I. A collection of the raw materials from which Portland cement is manufactured, together with samples of this material taken in various stages of manufacture, to the finished product. 2. A collection of the various sands, gravels, cinders, broken stone and metal used in concrete, together with photographs and models of structures built of concrete in all parts of the world. 3. A library of books and files of the various technical journals devoted to cement, mortar and concrete. lºt | | | | || - |mºſº | - º Fig. 3 –View of Cement and Concrete Materials Exhibit 4. A completely equipped model testing laboratory. 5. A collection of machines for mixing and molding concrete; and, 6. A collection showing the many forms in which Portland cement is used. The exhibit building, one of two permanent structures, which has been presented to and accepted by the Park Commission"of the City of St. Louis, Mo., is an excellent example of reinforced 7 concrete construction, and consists of three pavilions separated by intermediate courts and connected across the front by a con- tinuous loggia, the roof of which is covered with cement tiling (Spanish pattern) of a rich red color. This coloring, together with the red tinting of the ceiling of the loggia, relieve the general grey tone of the walls and forms an agreeable color contrast. The style, Spanish Mission, and the rough-finished walls are particu- larly well adapted to the use of concrete. As much interest was manifested in the finish of the walls, a description of the method used is added. The forms were re- moved at the end of twenty-four hours after casting and the out- side surface was then scrubbed with a soft wire brush, washing with a hose at the same time, this removed the cement and sand from the surface, leaving the stone of the concrete prominently exposed and producing the effect of rough casting. The advan- tages of this method are, first the production of a uniform color, and second the prevention of the appearance of hair cracks by the removal of the excess of neat cement. t The superstructure of reinforced concrete rests on a sub- structure of concrete, carried to a Solid foundation, reaching in some portions a depth of 16 feet. American Portland Cement, Mississippi River Sand, chatts (the screened tailings from the Missouri lead mines) and broken stone were used in the concrete in proportions of One part Cement, three parts Sand, and six parts broken stone for the substructure, and one part cement, two parts sand, and four parts chatts for the Superstructure. The roofs, covering the pavilions, are of ferro-inclave con- struction, 3 in. thick; consisting of corrugated sheet iron plastered on both sides with a mixture of Portland cement and sand. The walls are reinforced every foot, both horizontally and vertically, by 4-in. round rods. The beams of 30-ft. span have 23-in. diameter round rods, in the upper and 2%-in. rods in the lower portion. For the 20-ft. beams 3-in. round rods are used, in the upper and 3-in. rods in the lower portion. The stirrups are I+-in. wide No. 16 gauge iron. The interior walls were floated while green with a mortar of cement and sand, and subsequently tinted with rich water colors, the reception rooms being finished a deep vermilion, the laboratory a warm terra-cotta, while the exhibition room is finished in a 8 deep green. The ceilings are uniformly of a rich cream color. Between the windows, bordering the interior courts, are medallions of the labels of the various companies, cast in Portland cement. The South end pavilion was used as a reception room and office, and contained a reference library of books and files of the leading technical journals devoted to cement, mortar and con- crete. The north end pavilion served as an exhibit room, in which was displayed the collection of the characteristic raw materials from various parts of this country used in the manufac- ture of Portland cement, showing raw material in the various stages of preparation to the finished product. The coal used was also shown in the raw and finished state. In all three pavilions were transparencies of some of the Portland cement plants in this country. The various forms of metal used in reinforceing concrete, the sand, gravel, cinders, and broken stone, from all over the country, were on exhibition. Besides, there was a collection of photographs of work built of concrete, from all over the world, and of tests made to establish the fire-resisting qualities of concrete. The wonderful growth of the Portland Cement Industry, the steadily increasing consumption of American Portland cement, and the decreasing consumption of natural and imported Port- land cement was shown graphically, while by means of maps a comparison was made between the plants in existence in 1890 and those in existence at the present time. The central pavilion contained a thoroughly modern and admirably equipped testing laboratory, the finest that has ever been installed in this country. This laboratory was in daily operation, demonstrating the methods used for testing cement and concrete. The mixing and molding were performed on two especially designed tables, each of which is 7 ft. long, 28 in. wide, and 3 ft. high at the main portion; each end (32 in. above the floor) has a one-inch plate-glass mixing slab 2 ft. Square. In the Central part of one of these tables a galvanized iron pan 2 ft. Square and 6 in. deep was inserted provided with a cloth-covered wire screen top, and a wooden rack in the bottom 3-in. high. The pan was filled with water to the top of the rack and the cloth was kept wet. The test pieces used in the determination of time of setting were 9 placed on this rack and kept there during the test, being removed from time to time to make trial tests of the setting. The object was to maintain the test piece under uniform conditions during the test. The tension and compression test pieces, as well as those for the soundness, were kept in moist air for the first 24 hours after molding. For this purpose there was a moist closet, which con- sisted of a soapstone box 4 ft. wide, 18 in. deep and 2 ft. high resting on a wooden frame 30 in. high. The closet has a Central vertical partition, and was provided with wooden doors covered with planished copper. The bottom was made water tight, and holds about 6 in. of water; the sides have cleats for holding four sets of glass shelves 4 in. wide, 22 in. long, on which were placed the molds containing the neat cement briquettes. At the bottom over the water is a wooden rack, on which were placed the molds containing the mortar briquettes. The test pieces were removed at the end of 24 hours, marked, removed from the molds, and for all tests for longer periods than 24 hours they were immersed in tanks. These tanks were of soapstone, provided with running water and were arranged in tiers of three each. There were six tanks in all, each 6 ft. 7 in. long, 30 in. wide. One of the upper tanks is 30 in. deep, and was used for the storage of large beams and cubes of concrete; the remaining tanks were all 6 in. deep (inside measure). Each tank was provided with two inlet and two outlet pipes, by which the water was maintained at any Constant level. An instantaneous gas water heater was connected to the supply so that the tempera- ture of the water could be maintained practically at 70° F. For the determination of time of setting and normal consis- tency there were two Vicat Needle apparatus, one made by Tinius Olsen and Company, and the other imported from Germany. For the tension tests there was a long and short lever machine. The former, made and loaned by Tinius Olsen and Company, of Philadelphia, was driven by an electric motor, and was auto- matic in the application of the weighing load; while in the other, made and loaned by the Fairbanks Machine Company, of New York, the load was applied by a stream of shot flowing into a bucket suspended to one of the levers, the slip of the clip on the briquette being taken up by means of a worm which operates the IO lower clip, a feature which has added very considerably to the value of this type of machine. For the compression tests there was a 40,000-pound, hand- driven machine built and loaned by the Falkenau-Sinclair Machine Company, of Philadelphia, and a 200,000-pound electric motor- driven machine built and loaned by Tinius Olsen and Company, of Philadelphia. This machine was equipped with table for transverse tests up to IO ft. Clear span, and was provided with a ball and socket bed plate for compression tests up to 12 in. The former machine was new, having been built especially for this exhibit, at the request and under the supervision of the writer. The proper way for testing cement mortars or concretes is in compression, as it approaches more nearly the conditions of actual use. When we design structures in concrete, we disre- gard the tensile strength of the concrete, and figure entirely on the Compressive strength, incorporating in the beam or column sufficient metal to take up the tensile stresses. Why then should we test cement in tension ? We will find the reason in practical rather than theoretical conditions. The average laboratory, or more specifically, the usual laboratory of the consumer, is not provided with a large fund for its equipment or operation. The usual machines used for tests of strength are the tensile testing machines, ranging in price from $90 to $200. The compression machines sell for from $800 up, besides requiring power for their operation. Their cost places these machines beyond the reach of all except the large permanent laboratories. The 40,000-pound machine, in the laboratory will sell for $300. It is to be hoped that under favorable cost conditions, compression tests will come into increasing favor, and in time supplant the unsatisfactory tension tests. It is an encouraging fact, and worthy of note in passing, that tests of cement are being regarded of much greater importance and are receiving correspondingly greater attention than formerly. This is unquestionably the result of the increasing and varied application of cement for constructive purposes, and under con- ditions which render the quality of the cement of paramount importance. The most important test that can be applied to cement is that for soundness or constancy of volume, as it is of the highest importance • g * º & * * *. • * : * , e * J I that a cement once set shall remain volume-constant. No en- tirely satisfactory test has been devised for this purpose. In the apparatus used in this laboratory the pats were placed on a rack, over boiling water, the surface of which was kept constant by means of a constant level bottle. The pats were maintained in an at- mosphere of steam at a normal pressure. No matter what the character of the water may be, the steam will be pure, and thus free from the objectionable feautres that may enter into the boiling test. The laboratory was provided with the usual standard sieves: Nos. IOO and 200 for Cement; Nos. Io, 20, 30, 40, 50, 60, 80, Too and 200 for sands, and with an analytical balance and scales, with the necessary metric weights, made and loaned by Henry Troemner, of Philadelphia. For the specific gravity determina- tions the Le Chatelier's apparatus was used. There was also a Bauschinger apparatus for measuring the expansion of cement, and the usual measuring devices for the various tests. In the rear of the building were the outside exhibits which served to illustrate a few of the many uses to which Portland cement is put, and some of the methods employed in mixing and molding. The flexibility of reinforced concrete construction was illus- trated by a cantilever beam exhibited by the Hennebique Con- struction Company of New York, and which was tested to destruction as described hereafter. . . . . . . Adjoining this cantilever was an exhibit of the Siegwart hollow reinforced beams, by John E. Olsen, of New York. The Trussed Concrete Steel Company, of Detroit, Michigan, made a series of test beams and erected a floor system, the latter a combination of hollow tile and concrete beams, and also some columns supporting a beam, all serving to illustrate the “Kahn System”. The tests of these beams and floor slab are also described hereafter. A floor panel between two steel beams, resting on concrete piers, served to illustrate The Roebling Construction Company, of New York, system of fireproof flooring. - The Truss Metal Lath Company, of New York, showed a section of partition, illustrating the use of the Truss metal lath. I2 Ornamental work in cement was illustrated by the Algonite Stone Company, of St. Louis. The exhibit comprised a porch consisting of two Columns and two pilasters, Supporting a pedi- ment and roof; these pilasters and Columns were connected on each side of the porch by a balustrade. Several steps led to the porch floor. They also exhibited a Corinthian column cap, and a cap for a pilaster and other forms of artificial stone work. The National Art Stone Company, of Chester, Pa., displayed an ornamental mantel and column; the feature of the exhibit was the extremely low percentage of cement used. Samples were exhibited containing only three, Seven and ten perecent. of cement, and ninety-seven, ninety-three and ninety per cent. of Sand. The Art Mosaic Tile Company, of St. Louis, displayed mo- saic work in Portland cement; they had a fireplace, a kitchen sink, and flooring tiles. The Vulcanite Paving Company, of Philadelphia, showed a section of granolithic pavement, and a section of steel-bound concrete curbing. Concrete railroad ties were exhibited by Casper Buhrer, of Sandusky, Ohio, and Frank Ford, of Albion, Mich. The former were made of old rails with the head bedded in the con- crete and with the flange up, the latter serving as the bearing and means of holding the rail in place. They have been in service in the Lake Shore and Michigan Southern Railroad for over two years. They have also been used by a number of other railroads. The Ford tie was in two pieces, connected by a rod insulated at the connection. Reinforced concrete fence posts were exhibited by H. T. McCarthy, of Detroit, Mich. The reinforced concrete burial vault, shown by George A. Rackle and Sons, of Cleveland, Ohio, marked a new feature in burial practice, having advantages over the wooden casket The Kielberg pipe of Danish manufacture (made with a hydraulic press) was exhibited by F. L. Smith and Company of New York City, the American agents. The pipe was of excellent quality, and stood the long transportation without dam- age. , Jº I3 The hollow building block machines were exhibited by H. S. Palmer, of Washington, D. C., the Cement Machinery Com- pany, of Jackson, Mich., and the Burlington Block Machine Com- pany, of Burlington, Iowa. These machines were in operation daily, demonstrating the manufacture of cement blocks. The two-piece block was exhibited by the American Hy- draulic Stone Company, of Denver, Colo. Walls of various thickness from three inches and upwards were shown. Cement brick and cement paving tile machines were operated by A. D. Mackay, of Chicago, Ill.; while cement roofing tile is displayed by the American Cement Tile Manufacturing Company, of Wampum, Pa.; Brock Bros., of St. Louis; and Furman Construction Company, of Detroit, Mich. The Brock tile is plain, the American is made corrugated, diamond-shaped and in the four-foot plain form, while the Furman is diamond- shaped. The Municipal Engineering and Contracting Company and the McKelvey Concrete Mixer Company, of Chicago, had exhibits of concrete mixers. The former was a cubical mixer, mounted on wheels, and was complete with boiler and engine for operating. The McKelvey mixer was a hand-driven barrel machine. The limited time available after the completion of the exhibit was insufficient for the execution of any elaborate series of investi- gations. It became necessary, therefore, to concentrate the work on such tests as would be productive of data of the greatest value. The tests made were of two kinds: those made in the laboratory and those made among the outside exhibits, consisting for the most part of full size concrete beams and floor slabs which were loaded to destruction with pig iron. The work in the laboratory was confined to illustrating proper methods for testing cement and to investigations of the comparative value of the various sands, gravels, and broken stone used in some of the principal cities of this country. Inasmuch as the exhibit was the joint work of some forty Port- land cement companies it was deemed undesirable to advertise any particular company either by permitting individual exhibits or by the use of a particular brand. The building was built with cement which was a mixture of four brands of Portland cement, I4 readily found in the St. Louis market. The same policy was fol- lowed in the cement used in the laboratory tests; in which case a 350 300 850 200 700 650 600 550 7 Days. 850 800 750 700 650 £8 Days. 900 850 800 750 ENG, NEWS. 2 Morſ f/75. Neot Cemen f. thorough mixture was made of five brands, which gave a standard Portland cement of sufficient quan- tity for the entire series of tests. It is a rather curious fact, that the average of the tests of the mix- ture of the five brands was higher than the average of the tests of the individual brands. The result of these tests is summarized in Table I, page 16. The variations in 400 350 300 250 7 Days º 300 250 200 23 Days * 350 300 2 Mor/f/75 . Three Ports Stondo, rd Offo wo. 60 no. FIG. 4.—Diagrams of Results of Tests of Cements and Mortars, Showing Effect of “Personal Equation.” I5 the results of these tests are due to two causes: (1) Changes in the quality of the cement due to atmospheric conditions, and (2) changes occasioned by the variation in the “personal equation” of the operator. Two men made the same tests simultaneously, using similar apparatus and methods. The effect of the “personal equation” and other changes is set forth in the diagrams Fig. 4;” the ordinates being the successive tests as made, practically, at daily intervals. These men were inex- perienced in the beginning and it will be noted in the diagram that while the results were far apart in the beginning they became more Concordant as experience was acquired. In the comparative tests with the standard cement, of sands, gravel, and broken stone it was only possible in the limited time to test those from the following points: Berkshire, Mass.; Cleveland, Ohio; Cowe Bay, Long Island, N. Y.; Chicago, Ill.; Dallas, Tex.; Kaw River, Iola, Kan.; Philadelphia, Pa.; Plum Island, Boston, Mass.; St. Louis, Mo. The results of these tests will be found in Tables III, IV, V, Pl. I, opposite page 16, and diagram Fig. 5, page 17. A study of the latteris quite interesting in that it shows the relation between the size of the particles and the percentage of voids. The tests seem to indicate that the Smaller this percentage the greater is the Strength of the mass; this percentage being dependent on the size of the particles. Where the particles are well graded from coarse to fine, the percentage of voids is reduced to a minimum. This was found to be true of the unscreened sands and gravels, the highest results being obtained with the sand or gravel containing the least percentage of voids and showing the best gradation in the size of particles from coarse to fine. - When this material is screened to one size as 20–30 the per cent. of voids and the strength become practically the same, re- gardless of the strength previously obtained with the unscreened material. In this particular it apparently matters not what the geological origin of the material is, provided it is not undergoing further decomposition. It is also observable that the specific gravity of the sands and gravels is practically the same. An examination of Table IV will show the very small percentage *Acknowledgment is made to the Engineering News for the cuts used in this paper. sample "“” rule or serrine TEN S I L E StrP E N G TH POUND 9. PER SQUARE 1 NCH !N P ºr R C & NT at cºr NUMBER [REsioUE in sievº i N M N UTE: 8 warER N EAT SAND av ERA GE ANyºrag E Avtº RAG: |AVRRA6 No looj No. 200 || NITIAL | H ARC ! oaºr §3.jº, 7 DAY's ºf;...] as DAYS |º]?:- 7 DAY's lºgº.º. 2 e DAY's ºl. |º A 3.8 s-|2 cº-| 27°- smo- || 1s'z |ur is 17|ne 12 s saz s” ssosºs |sse e70 ee" 7831712 |zoe 155 iso 17o|1ée iss|2s2 2so 2ss|24° es: A º. 1 & 25.QO || 28 6. 436, *** 1142 ºz.4 133 | 1.33 53° S.7° 46, 51.529 69C 73 o 6°oſ 700 | 65 I SO 26 ||47 277 295 263 |275 E. 8.8 o- 25, 53- 58 - in o- || 20'2 rsa zos 22 of 22 o 23.5° 59 J & oz & J S 6 o'S ©28 zºo 7se 776||776|zes 287 zes 279|274|zesłºsz 423 ase].” o | 1 to SS ! 2 oo Wº H \l-A. BAN YO SANA O | | | So * { ſº tº TABLE eys strº. * B = 75 i 2.3, o 2S 5 \ 37.5 | 3 || ! 34.3 wººl 4. |4-58, G.7 * *-Cº a 12. \ass $4.63 | 4-OC |4-5° loº 5 | \o 3, ! I | 8 \ 5 * 2 &o 11 G 8, | | 5 3 \ \ 4-3 | | 2.2 O \o 1 a | | O 5 V—Comparative Compressive Strengths 22 ozº 22 Ty º, 2 º 2. 133 138 2. 173 || 2 || 3–5 275 o 271 3 395 A 15 4 tº yº. 34. Sºo | S 1 | 4-oo 1632|2898 |S.4 o 2. 7.5 3 & 13 I tº 3 Sz.5 23 | 7-7 o 7 o'S |S 1 a J3 os 3748 | | || 3, | \Goo ! Soo ! 3 33 | | So 75 | 3 | 3, Strength of Mortars Made of Sands of the Composition Shown | | Q 3, | 2.J. 2c | 2 || Tº ! { { I 2-3 W2.8, 3. 12.3 o l 2-13 ! o 83 \o oo | J J & Sº 1. i2. 2.7 C, 2.13 ºn 5 ~ O & 3 gº 31 A. in Table II. W 2 TVo W.So \ º 22d. t '*** 12 q+ ! cºs"? ſo ºr S | 2. 2.7 S 7 7 & 23 oo 23 So 2 23&º 2 × 7.5 2. Soo 2 ö \ & 4-4. 2. 12.3 × ooo 2. *7 o 2 £, # "fºnd Bars Berry ENG. NEYv5. BEAM 3, HENNEBIQUE SYSTEM.—Length over all, II ft. II; ins.; clear span, Io ft.; breadth, 12% ins.; depth over all, 9 ins.; depth to center of steel, 7% ins.; weight of beam, 876 lbs.; mixture, 1:2:4; strength of beam, 60 days, 1,747 1bs. per sq. in. Loads, Deflection. lbs. in. Remarks. 235o I-8 435o 5-32 635o 3-8 79.5o I 5–3.2 First hair cracks appeared in center. 835o 9-I6 . 87.5o 7-8 Failed by concrete crushing at top in center of beam. 21 ,...??:Foº/*35 2bſ -...ſºvº&##eº, ygºy"Fºº- # Ti". ---.º. JS º * * = R r--------|--|z-I- r--- -- ====== # # †† { : ; J. f L * | l !. 3--4--- j- ...t *:::::::::: &: f: 3.2%-> ſºft'Aº: Sø3 Stirruas No.206aºlº evary/37 E:4G. NEWS. BEAM 4, HENNEBIQUE SystEM.—Length over all, 12 ft. 3 in. ; clear span, Io ft.; breadth, 6% ins.; depth over all, 8% ins.; depth to center steel, 7} ins.; weight of beam, 61.4 lbs.; mixture, I : 2: 4; compressive Strength, 60 days, 1,747 1bs. per Sq. in. Steel in tension . . . . . . . . . . . . . . . . . . . . . . . . . I.60% Steel in compression . . . . . . . . . . . . . . . . . . . . . .80% Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40% Loads Deflection. lbs. in. Remarks. I 35o I-I 6 235o I-8 33.5 O 3-I 6 435 O 7-32 5350 3-8 635o I-2 Faint hair cracks on either side, center very faint. 735o I9–32 835o I 3-I 6 865 o I Failure by concrete buckling at top in center. An average of several tests of the # inch round rods used in beams 2, 3 and 4 is as follows: Elastic limit 41,500 lbs; modulus of elasticity 28, ooo, ooo; ultimate strengh 60,500 lbs., elongation in 8 inches 25%; reduction of area 61% fracture, angular, silky, blueish-grey color: surface pitted and rusty. In the space adjacent to the Exhibit building there had been planned an elaborate series of test beams built according to the various systems in use in this country. Unfortunately, the exhibit was completed so late that it was impossible to stir up sufficient interest to carry out an elaborate program. Besides, there were no funds available for such experiments, and the expenses Connected with the tests which were made were very generously borne by the Trussed. Concrete Steel Co., of Detroit, Mich., and The Henne- bique Construction Co., of New York, to whom the writer wishes to express his thorough appreciation and thanks for the interest taken and the assistance rendered by them in the experiments. The tests in question consisted in reinforced concrete beams and floor slabs of 15 ft. span and a cantilever. Simultaneous with the making of the test beams 6-in. cubes were made from the concrete which was used in making the beam and floor slabs. The results of these tests are found in Table II, page 16. 22 The chatts which were used were a calcareous chert, all of which passed a No. Io screen. There are two varieties of chatts, a hard silicious chert which comes from Joplin, Mo., and the soft calcareous chert which comes from Bonne Terre, Mo. This ma- terial is the refuse from the lead mines and as it is relatively cheap it is extensively used in St. Louis and vicinity. The chatts used was of the calcareous variety and were quite soft and friable, having a low compressive strength and therefore making a con- Crete correspondingly poor. It was for this reason that the beams tested failed in many cases under a small load before the strength of the steel was de- veloped. It will be noted that the cinder concrete gave correspondingly low results. The cinder was clean and of a better quality than is generally used—although it contained a large quantity of unburned coal. The strength of the concrete in which it was used was about one-half of that of a good stone concrete. The modulus of elasticity was about 1,500,000 in the concrete made with chatts and 500,000 for the cinder concrete—values materially lower than are usually quoted. These tests show how important it is to have a hard aggregate in order to secure a strong concrete. An important feature gener- ally overlooked in tests of concrete is the compressive strength of the aggregate itself. If a test of the aggregate was made it would serve as a basis for comparing the compressive resistance of con- Crete and would indicate whether the difference was due to differ- ences in the strength of the aggregate or was due to the mixing or to character of the other aggregates. The concrete for the beams and floor slabs was mixed by hand in the proportion of one part Portland cement, two parts Missis- sippi River sand and four parts chatts; wooden forms were used and were thoroughly wetted before the sloppy wet concrete was deposited in them. The concrete was not subsequently wetted and the forms were removed at the end of ten days. They remained in air, unprotected, and were not handled until tested at the end of about 60 days, when they were loaded to destruction with pig iron. This method is a slow, laborious process requiring the exercise of great care in loading so as to maintain the center of gravity of the load over the center of the beam, but there were no 23 other means available for testing these beams of such large size and Span. The overturning which occurred in the case of A and B was produced by the unequal compression of the earth under the bear- ings supporting the beams. Possibly, this will also account for the shearing of the overhanging un-reinforced slab in the T beam F. The ground on which the beams were built had been filled in with the refuse staff, scaffolding, etc., from the Exposition build- ings and in proportioning the bearing area insufficient allowance was made for the compressibility of this filling. In order to avoid arching of the pig iron, through the deflec- tion of the beam under load, the pig iron was placed in piles and sufficient clearance was left between the piles so that the deflection would not bring them into contact. Where the load required to break the beam is large, these piles are quite high (for A and B they were 5 ft.), the piling of the pig becomes slower and the maintenance of the equilibrium much more difficult as the height increases. The rate of loading varied from 50 lbs. to 150 lbs. per minute. The deflections were measured at the center from a string stretched taut over two wire nails in the side of the beam imme- diately over the edge of the support and in the center line of the bottom reinforcing steel. The following are the results of the tests of these beams: BEAM F.—Built Sept. 13; tested Dec. 1, 1904. Length Over all, I 7 ft.; clear span, 15 ft.; breadth at base, 8 ins. ; at top, 18 ins. ; depth over all, 13% ins.; depth to center of steel, 113 ins.; reinforcement in bot- tom, two I-in. round bars, with One I-in. round bar just above; mixture, I : 2: 4; weight of beam, 2,529 1bs., compressive strength of concrete, 1,740 lbs. per sq. in., per cent. Of Steel, I.63, area of steel, 2.35 sq. ins. Loads. Deflection. Time. lbs. 111. Remarks. Io.5o A. M. 3656 3-I 6 I 1.35 “ 6877 3-I 6 I 1.5o “ 8997 I-4 12.oo Noon. Io8o 7 I.o 5 P. M. I4 IO 5 7-16 1.4o “ 18898 9-I6 Two hair cracks I ft. off center line either side 2 o I 66 Failed. Bars sliding as beam collapsed, Fig. 7. The slab sheared off on one side as will be seen, this was probably due to lack of uniformity of *memºs-smºsºmºsºms-º-º-º-º-º-º-º-º-mºm. 3:2-ºº:::tº:*:::::\ºti ====ºr=ws==== 2 *J * w *, * *, * g- *_* * Y * ,” S. * N Y, N Sººsz, X. X 2. X />. zŽs 42: %:ºrs ,” .." * ,’ ,” N N. * * ^ *Sºur:-- * * z '---fºr. * * ar * «» * \ N *s *~ -ar: “ss. *, ,' sº-> == 42 ,” 2^ 2" * * * * *> - sº ---- ::::::: * ,’ …?/ 2’ ,” e º /5' 04----- º Bec, rn A. * * \ / A *:::::-> N *. * A * Z-2:2 ..., ~ N N Nºssy, N \ • A.Z.42% A A' A' 2 N * N N ºrs A sº-2-ºf 2 A ,’ / A Nº. * ==---- :-- ,” e , / ,” 2^ {-12 Af _* * / fy * ff º CTs /5 ' O /2 > E ecºrm. E. =s== ºS ^N. Z TV 2 X * X 7 z' "Sº-> ** ** * ^ ºv, Nº < sº ,” * *, / & N. &=== £==º, / * & / N * N Y. X Y. **** --> *::::::::: *:::::: A * A zº," 2.A A Af/ - /2 gº P / A/ Af K /5 O /2 >. Bec, rn C. *~ ** º * ===> \, \ * / A 4.----> N N * N N * **ssº--> ^ * A A £2-> *T2 2’ 2 2 * & \ X. N SN X, N X, N *º-sº sº sº, \ sº- 4. -4---º A 2" 2^ 2' A A k /2 “L , cº- / f/ wf ** as /5 " O ---->k af /5' 0 a 4. w Ž| % 2% /4" 2 // // z 22/ {Z}// 2%% #% º, , , " Z. z’ - - % º --4- * --Kºz ŽižS. Ż| /'0" %|''. 2,”z, Zz tf 3.32% ºſſ 7 '2 FIG. 8-Diagrams of Test Beams and Floor Slab Showing Dimensions E ec, rn E ec, nºn F. * f.A. f* K---------58-ris X, X, \ `, Y * 2’ ,’ 2" 2’ ,” ,’ 2 £z [...] 2 [[] jºr Aº |-->====--->===>~-As--->===s.ºº::::::::::::=== A A 2 <= <<<- %ti- %Hit lſo // ×4% /'0">4k/'0"> {<\º K9 -k /6’ 64 ". i, , , a " 2.”]s tir, G : tº ENNS., 9 */4 */4">S and Reinforcement. 25 load. The bars did not slip until the beam collapsed There was no reinforcing in the slab. The dimensions of beam and other information can be obtained from Fig 8, page 24. BEAM E-Built Sept. 13; tested, Dec. 1, 1904. Length over all, 17 ft.; clear span, 15 ft.; breadth, 12 ins.; depth over all, 13% ins; depth to center of steel, 12 ins.; weight of beam, 2,677 lbs.; mixture, 1: 2: 4; Fig. 7-View of, End of Beam E. Showing Shearing Off of Slab and Sliding of Reinforcing Rods. compressive strength of concrete, 1,740 lbs. per sq. in...; reinforcement in bottom, three 1-in, round bars 17 ft. long; area of steel, 2.35 sq. ins. : per cent, 1.63. Loads. Deflection. ine. lbs. sq. in. 1n. Remarks. 9.oo A. M. 165 Io 9-32 Deflection not noticed before 1,000 lbs. 12.oo Noon. 2d 166 II-32 24.612 IS-32 5:30 P. M. 26460 I-2 26 Loads Deflection. Time. lbs. sq. in. 1n. Remarks. Dec. 2d. 8.30 A. M. 33 198 2I-32 8.30 “ 2646.0 11-16 Two hair cracks, one on either side of the center line. 33ro8 Failed. A series of vertical cracks appeared until the beam failed suddenly by horizontal shear at one end entirely. Bars again slipped as beam collapsed. Dimensions of beam given in Fig. 8, page 24. Fig. 9 shows beam after failure. Dimensions, etc., see Fig. 8. - - - - FIG. 9.-View of End of Beam E. Showing Sliding of Reinforcement. BEAM D.—Built Sept. 13; tested, Dec. 2, 3, 1904; Length over all, 17 ft.; clear span, 15 ft.; breadth, 12 ins.; depth over all, 13% ins; depth to center of steel, 12 ins; weight of beam, 2,677 1bs., mixture, 1: 2: 4; reinforcement in bottom, two 3-in. Kahn bars 17 ft. long; reinforcement in bottom, one -in. Kahn bar 9 ft. long, bent up slightly; area steel in tension, 2.34 sq. ins.; per cent of steel, 1.63; compressive strength of concrete, 1,740 lbs. per sq. in. 27 Loads. Deflection. Time. lbs. 1I].S. Remarks. Dec. 2d. 3.30 P. M. 6479 I-I 6 3.5o “ 846 I 3-32 5.oo “ II 8o0 I-4 5.30 “ I5o 33 I I-32 Dec. 3d. 8.30 A. M. ISO 33 I I-I 6 8.55 “ 2 o'732 3-8 9.3o “ 23476 I-2 Io.30 “ 278oo I I-I 6 II.3o “ 3O 7 I 9 I in. II.45 “ 3.2663 I# in. II.5o “ 32663 Failed slowly 4 ft. 6 ins. from each end of beam. Dimensions, etc., see Fig. 8. BEAM C.—Built Sept. 12; tested, Dec. 3, 4, 5, 1904. Length over all, I 7 ft.; clear span, I 5 ft.; breadth, 12 ins. ; depth Over all, I 3% ins. ; depth to center of steel, 12 ins. ; weight of beam, 2,677 1bs.; mixture, 1: 2: 4; reinforcement in bottom, two 3-in. Kahn bars I 7 ft. long; reinforce- ment in bottom, one #-in Kahn bar 9 ft. long, bent up slightly; reinforce- ment in top, two 3-in. Kahn bars 9 ft. inverted; area of steel in tension, 2.34 Sq. ins. ; area of steel in compression, .76 sq. in. ; total area of steel, 3. Io sq. ins. ; per cent. of steel, 2.15; compressive strength of concrete, 1,74o 1bs. per sq. in. Load. Deflection. Time. lbs. ins. Remarks. Dec. 3. 3. Io P. M. 5629 I-32 3.5o “ II 398 3-I 6 4.20 “ I 5287 3-8 Dec. 5. Nothing done. Sunday. Dec. 6. 8.oo A. M. I 5287 3-8 8.30 “ I8 Ioo 3-8 9.oo “ 2 I 688 I5-32 Hair cracks appearing. 9.3o “ 24o 58 5-8 9.55 “ 29943 7-8 I o.o.5 “ 28934 I Io. Io “ 299 I4 I} 1 o. I 5 “ 30878 I-I I-16 to 25 “ . . . . . . . . Failed. Dimensions, etc., shown in Fig. 8. 28 BEAM B.—Built Sept. 12; tested, Dec. 5, 6, 1904. Length over all, 17 ft.; clear span, 15 ft.; breadth, 16 ins. ; depth over all, 17% ins.; depth to center of steel, I 6 ins. ; reinforcement in bottom, two I-in. Kahn bars 17 ft. long; reinforcement in bottom, one #-in. Kahn bar 9 ft. long, bent slightly upwards; area of steel, 3.62 sq. ins. or 1.41%; weight of beam, 4,600 1bs.; mixture, I : 2: 4; compressive strength of concrete, 1,740 1bs. per Sq. in. Load. Deflection. Time. lbs. ins. Remarks. Dec. 5. 2.oo P. M. Io.4I 7 I-I 6 2.30 “ I 5.189 3-32 3.2 o “ 228o 2 7-32 4. Io “ 27.607 9-32 4.45 “ 3I487 1 I-32 One hair crack on bottom of beam under each bent bar. Dec. 6. 8.30 A. M. 3I487 I I-32 9.35 “ 33.403 II-32 Two more hair cracks appeared. Io.5o “ 38 I 90 I I-32 12.45 P. M. 45082 I 5–32 1.3 o “ 47817 3-4 Two more hair cracks appeared nearer bearings. 2. Io “ 5oooo 7-8 3. Io “ 54735 I-I I-32 557 27 I– 7-I6 567 I 2 I-I 9-32 3.5o “ 57696 I–II-I6 58675 I-3 I-32 4. I5 “ 5.9906 2 5.oo “ 609 II 2–1 I-32 Beam overturned. Dimensions, etc., see Fig. 8. BEAM A.—Built Sept. 13, 1904; tested, Dec. 7–14, 1904. Length over all, 17 ft.; clear span, 15 ft.; breadth, 16 ins.; depth over all, 17% ins.; depth to center of steel, 16 ins.; reinforcement in bottom, two 1-in. Kahn bars 17 ft. long; reinforcement in center, one #-in. Kahn bar 9 ft. long, bent up slightly; reinforcement in top, two #-in. Kahn bars 9 ft. long, inverted; weight of beam, 4,600 1bs. ; mixture, I : 2: 4; area steel in tension, 3.62 or 1.41%; area steel in compression, 1.56 or .60% ; total steel, 5.18 or 2. Io96; compressive strength of concrete, 1,740 1bs. per sq. in. Hºs. Deflection. Time. bs. 111. Remarks. Dec. 7: . 9.25 A. M. Started. Io.45 “ IoI 68 I-I 6 { { II.4 O I 5937 3-32 29 Hºls. Deflection. Time. bs. 1Il. Remarks. 2.25 P. M. 2 o'769 S-32 3. Io “ 25632 3-I 6 3.25 “ 27617 3-I6 3.55 “ 3 I 548 3-I6 4.3o “ 3356 I 3-I6 4.45 “ 35.477 7-32 5.oo “ 37.458 7-32 Two faint hair cracks, one at each end of bent bar in center; beam started to Overturn, bearings sinking unequally. Dec. 8: Unloaded and straightened. No deflection observable, then began loading. Dec. 9: 8.3o A. M. 37.458 7-32 9.45 “ 40839 7-32 Io.35 “ 44723 I-4 Four hair cracks (2 more) on each side of center. I 1.25 “ 5oooo 5-16 Rain stopped, loading beam Over- turned, due to unequal settling of foundations. 52693 Dec. II: 52962 3-32 Set in beam. 54945 I 3-32 60856 5-8 Beam overturned. Foundations again settling unequally, beam straightened, one hair crack in center, 2, 3 ft. 6 ins. On either side of center of beam; #-in deflec- tion set in beam. Foundations releveled bearing area increased and beam reloaded. Dec. 12: Sunday—Nothing done. Dec. 13: II. I 5 A. M. 60856 3-8 Set in beam. Several hair cracks from top #-in. opening traveling off in both direc- tions horizontally, middle each 8% ins. from top. 6381 I Two more hair cracks appeared on either side of center line. Loads. Deflection. Time. lbs. 1Il. Remarks 66o 2 I 3-4 3.45 P. M. 7494I I–I-8 # 75ooo One crack 18 ins. from center line, 9 ins. from top. One crack 36 ins. from center line, I I inches from top. One crack 56 ins. from center line, 7 inches from top. 5.oo P. M. 8oooo I-3-8 30 Loads. Deflection. lbs. - Time. 111. Remarks. Dec. 14: S.o.o A. M. Soooo 1-3-4 81oro 1-13-16 82dos 1-13-16 83oos I– 7-8 83.977 1- 7–8 11.30 A. M. 854 oo 1-7-8 12.oo Noon. 87,385 2– 1-32 1.25 P. M. 90.362 2- 5-8 2.15 “ 93.269 3- 1-8 2.30 “ 94 of 4 3– 5-16 2.4o “ 945 I:2 Failed Weight beam 4600 Total load, 901 12 FIG. Io.—View of Kahn Beam A. Under Load Kahn System Hollow Tile Floor Construction.—Built Sept. 21, tested Nov. 30, Dec. 1, 2, 1904. Length over all, 18 ft. Clear span 16 ft. 6 ins. Width, 5 ft. 8 ins. Depth, Io ins. Tile, Iox 12 ins. Beam joists, five, 4 x Io ins., 18 ft. long, 1' 4" centers. 3 I Reinforcement, each joist, one 3-in. Mixture, I : 3 : 5. cent. Kahn bar, 18 ft. long. Area steel, each joist, o.78 in. or 2.30 per Weight of slab, 5,8oo-lbs. Fig 1 tº View of Kahn Hollow Tile Floor. After Failure. Time. Nov. 3o: 4. Io P. M. 4-45 -- 5. Io -- Loads. lbs. I 2457 1830.o 222 Oo 5.3 o -- Dec. 1: 8.30 A. M. 5-3o Dec. 2: 8.30 A. M. II. 25 So 25 I 32 25 I 32 25 I 32 25 I 32 25 I 32 34634 Deflection. 111s. n. 3-32 S. 3-32 I-8 3-32 I-2 3-8 5-8 3-8 3-4 9-16 3-4 2I-32 3-4 23-32 25–32 3-4 2-I-2 Remarks. Hair cracks across center ex- actly. Two vertical cracks appeared 3 ins off center line on either side. I 1.55 A. M. 356II Concrete commenced to crush on top over 1ast cracks loading stopped, beam kept cracking and slowly deflected until it failed at I 2.15 (20 minutes) with center cracks opening up and another 7 ft. off centre line concrete at center crushing out and a crack running along line of steel from center to right three feet. Breaking load 5oo 1bs. per sq. foot. The dimensions of slab are shown in Fig. 8, page 24, Fig. I I shows floor after failure. Siegwart Floor.—Length over all I4 ft. 3% ins., clear span 13 ft. 5% ins., depth 6 ins., width of slab 33 ins. ‘. Cº b ," *%"fſansome ſods.” Load. Deflection. Time. lbs. in. Remarks. 8.30 A. M. 29 or I-8 9. I 5 “ 5484 5-I 6 9.25 “ 8409 I – 2 Hair cracks well distributed along bottom beam. Io 378 I 3-I 6 II 366 7-8 & & IO.O 5 I 53 I 3 I-23-32 I 6284 2–3–4 Io. I 5 “ I 683 I Failed. This floor slab was composed of beams made according to Siegwart System; in above sketch the slab is seen to be composed of three slabs II x 6 ins. in section, and reinforced with rods ac- cording to Hennebique System without shear straps. The beams are cast around cores (core openings shown in sketch), the steel being placed in position and the concrete cast around it; the cores are withdrawn and the beams feathered apart at the points indi- cated. These beams were made in New York, and were shipped by express when 60 days old to the exhibit, where they were placed in position and the joints grouted. A load of bags of sand was placed on the floor (Ioo lbs. per sq. ft.) and remained there until the close of the Exposition, when it was loaded with pig iron to destruction, the beams being about 6 months old. The idea of this system is to make the beams for certain loads and spans and carry them in stock as steel I-beams are carried, shipping on Order. Cantilever.—This is shown in Fig. 12 and was built to illustrate the flexibility of reinforced concrete, the dimensions and rein- 33 forcement are shown in Figs. 13, 14 and 15. The stairway hung free and led to the top which was a walk; this was in service during the Exposition. Esenses Fig. 12.-View of Reinforced Concrete Cantilever Tested to Destruction The cantilever was built, as was discovered afterwards, OVer a wooden box drain and the settlement of the foundation caused the cantilever to tilt towards the outer end. --------- -330° > ! ... Hº. k---------------------------------------------- 28'0"----------------------------------> south Kºº North 2 * . § +- ~. - : - Sk–50°- - º § -> * *F, -ST i- - - º, SS ºrrº- tºº. I º -., ... F//ed Ground nºw- K- 150"-- >K-30°-ºf-110 W. -------- -> 5 ic e E levci tic n. FIG 13 3-4 The forms, instead of being removed gradually, were quickly removed, and the sudden application of the load caused a strain *Y- s : ; S. < tº º - - —/3 !--- - - º > S. º }- l p l l $ fº Ol Ol nº |<--|--26%----------> ENG. NEyvs. : : : | ©! Oh IO | Q O O On bol C O O O | End Elevction, North. FIG. I.4. 5/-. 9/72-73, #70/7/77.- 3 Sl z-z-z-z-z-z-z-z-z-z-z-z-z- x++++-r-z-z-z-z-z-z-z-y-y-y z tººzzzzzzzzzzzzzzzzzzzzzzzzzzº & 4 & & * º ::::::22zzzzzzzzzzzzzzzzzzzzzzzzzzz * * * * * * * * * * g e - -- - - - - - - - - = = = = = * * * * * * * * * * * * * * z & 777.27772-27.222, ZZZZ,22222222, 2222222 2, 2 ZZ22 / 2 2/2.2.2 ^2222222222222 tºº. 735.2272.2777.2772:22:22:272. Sºº 2-22222222222222222 ZZZzzzz ze, , z//22///, Z 22 A ^z º.º. ZZZZZ ***, *zzzzz z/22 ºzz, Z/, // 22.2/2 2, 2,1 * * * * 2 / 2, º 2 * e / e º z. z. 4A507//es 2. of Złºść Afrº - N #"/2am. J \s Q%2222*222222222222 ºzº • C_º - * * z e.e., za z e ºr 222222222 2/22 ºz/ / / / / / / / / / / / 2 4. /// Ž%%.4%%%22 = ~ * z - e 2 & e º ºr e º z º. 2 a e £º: Hj-.' 36% > 9%á'Zam.” 2/7063, # 'Zazz. Sec-i-ion A-B. FIG 15 which Cracked the cantilever at the shank on the left-hand side. The props were restored and the cantilever washed with neat A g zº 22222/ZZZZZZZZZZZZ *zzzzzz//e//////zzzzzzz z2, ... 1 & Kºź & #4 6ñods, #Dam. l ENG.NEWö, 35 cement. The props were then gradually removed and the canti- lever remained unchanged until tested with pig iron. The applica- tion of this load caused the cracks to open at left side of shank and the cantilever collapsed. As bars of the requisite size were not available a bundle of smaller rods was substituted; the shear members were insufficient to hold the cantilever and it pulled FIG. 16.-View Showing Failure of Reinforced Concrete Cantilever apart at the left shank and failed as shown in Fig. 16 before the compressive resistance of the concrete in the right center section of the shank had been reached. The loading was as follows: Loads. Deflection. lbs. in. Remarks 3ojo I-16 9845 I-4 I37.35 II-32 14760 Hair crack appeared. 1768o I-8 Opening at center I 1-16 in at outer end. 2 offo.7 Failed 4–1 I-16 in extension at the center. Besides these, tests were made of cement shingles, concrete sewer pipes, cement bricks and hollow blocks. 36 The Collective Portland Cement Exhibit and Model Testing Laboratory was assembled with a view of exploiting the American Portland Cement Industry and not with a view of advertising any particular process, plant or product. It was highly beneficial in disseminating a better knowledge of the proper methods of testing and of the nature, uses and properties of Portland cement; and in recognition of this fact it received two grand prizes, the highest awards of the Exposition.* It is to be regretted that the time available for the experimental work was not longer, so that much more data could have been obtained. It is, however, a matter of gratification to all those connected with this exhibit that the work thus started will be continued under the direction of the United States Government, the Joint Com- mittee on Concrete and Reinforced Concrete, and other inter- ested persons, and it is to be hoped that the exhaustive series of investigations of structural materials which have been planned under the direction of the National Advisory Board on Fuels and Structural Materials may be successfully carried out thereby supplying information of inestimable value to the engineering profession. *The Collective Portland Cement Exhibit was awarded a Grand Prize (see page 2 The Model Testing Laboratory received a second Grand Prize. UNIVERSITY OF MICHIG ill 791 O15 O7506 0 39 THE UNIVERSITY OF MICHIGAN DATE DUE *::::: -** º tº: § §§. º ..º. - t - | " ', ' '. F. ' : i h t . . . $ \ * i: ; ; '. t ! t q ! "| g : . : • . p | . . H. . . ; § {.{ . j !, | ! t * : .# s . t ; - t i | f * * * * n ; •; º t - º *** , º --- º, .