112 



The Philippine Journal of Science 



1913 



The maximum difference in the cost of the three cements was 

 only 2 centavos a barrel, or 1,500 pesos on the contract for 

 327,000 pesos. A low estimate of the total cost of the concrete 

 construction work is six times that of the cement, or 1,962,000 

 pesos. Fifteen hundred pesos represent only 0.076 per cent of 

 the total cost of the concrete; yet, other conditions being equal, 

 the difference of 1 per cent in the efficiency of the cement 

 represents, in durability and in strength of the concrete, a value 

 of 19,620 pesos. That there may be a difference in concrete effi- 

 ciency of as much as 25 per cent even between two cements of 

 the same brand, both of which pass the standard specifications, is 

 illustrated in Table III. The actual difference in representative 

 samples of two of the above cements is given in Tables I and II, 

 in which the cements are designated as No. 1 and No. 2. 



Table I. — Results obtained by subjecting two cements to the tests of the 

 specification of the American Society for Testing Materials. 



Test. 



Results. 



Sample 

 No. 1. 



Sample 

 No. 2. 



Specific gravity: 



Dried at 100 °C 



3.14 

 3.17 



3.08 

 3.19 







Composition: 



Per cent. 

 1.03 

 1.34 

 1.16 



Per cent. 

 2.94 

 2.83 

 1.19 









Fineness: 



Per cent. 

 87.0 

 97.8 



Per cent. 

 77.4 

 95.2 







Time of setting: 



Hours. 

 2.1 

 4.3 



Hours. 

 1.6 

 3.6 









sound 



sound 





Tensile strength: 



Pounds per 

 sg. inch. 



739 



745 



310 



422 



Pounds per 

 sg. inch. 



653 



707 

 313 

 379 













The figures in Table I prove that both cements passed all the 

 requirements of the specifications. However, sample No. 1 is 



