368 REIBLING AND REYES. 



exists the greatest amount of misconception and diversity of opinion, our 

 object being to assist in tire universal effort to improve cement specifica- 

 tions. It is our desire to affiliate our efforts with those of the American 

 Society for Testing Materials and with similar associations which are 

 endeavoring to formulate cement specifications so drawn as to guarantee 

 the manufacture and use of Portland cement of the quality sought for. 



The quality which we need in cement is constancy; constancy in satis- 

 factory setting properties, in volume, in strength, and in sand-carrying 

 capacity. The demands of modern construction work have also made it 

 "of vital importance that this material should not only harden rapidly 

 and attain a great strength, but what is far more essential, that it maintain 

 this strength." 2 However, sixty years of strenuous effort have failed to 

 perfect methods of testing or to produce specifications which will insure 

 a cement of this quality, or correctly to classify the various products in 

 their true order of merit. 



Our investigations were conducted on many grades and brands of mate- 

 rial. Pew places in the world offer a greater variety of cements than 

 Manila. Portland cement is not manufactured in the Philippines and 

 our tariff and location make it possible for cement manufacturers through- 

 out Europe, America, and the Orient to place their products on sale here 

 at almost identical prices, so that we had at our disposal brands of Port- 

 land cement manufactured in all parts of the world and representing 

 almost every class of raw material, process of manufacture, and degree 

 of sintering. These various products were sent to the laboratory, tested, 

 their characteristics noted and larger representative quantities then ob- 

 tained for research purposes. 



Each brand was mixed thoroughly and then preserved in 10-liter, 

 air-tight bottles until used. It was analyzed chemically and the physical 

 tests made which are outline in the specifications of the United States 

 Army (1902), the American Society for Testing Materials (1908), and 

 the Philippine Government (1908), 3 the strength and soundness deter- 

 minations being continued for one year. Each brand of cement was then 

 aerated, and from time to time repeatedly subjected to a like physical 

 examination. Tests of aerated samples were accompanied by similar 

 tests on the unaerated cement. These constituted only the foundation 

 for a more thorough investigation of the cause and significance of all 

 results not readily explainable. Microscopic, chemical, and ealorimetric 



'Humphrey, Richard L., Am, Soc. Testing Mat. (1902), 2, 160. 



s In all eases the temperature during manipulation and exposure was main- 

 tained between 25 and 30 degrees. The Philippine Government specifications of 

 1908 were identical in all other respects with those of the American Society, 

 except that a natural Philippine (Tarlac) sand, screened through a 20- and on a 

 30-mesh sieve was used instead of Ottawa sand. Recently standard Ottawa sand 

 has once more been adopted. 



