138 REIBLING AXD SALINGER. 



puts it: "We are all disposed to argue somewhat on the basis of our 

 prejudices or to refute othei's because of the prejudices which we associate 

 with theui. * * * Thei'efore it is difficult for us to arrive at conclu- 

 sions purely by the light of reason, and to deal with every syllogism 

 from its premises to its conclusions." 



However, the American Society of Civil Engineers and the American 

 Society for Testing Materials are constantly working to improve tlieir 

 cement specifications and these specifications will soon ])e adopted by 

 the Government of the Philippine Islands for all ci\il and municipal 

 work. They have accomplished much towards establishing a more prac- 

 tical impartial and comprehensive system of testing. Yet ''notwith- 

 standing that so much has been done towards unification of methods, it 

 may never be possible to determine accurately the value of one cement 

 as compared with another tested in a different laboratory".- "Experience 

 since the rejDort of the committee was made has shown that the difficulties 

 in the way of unifornuty in such tests are much greater then was then 

 imagined. The variation in the results of tensile strength Ijetween the 

 work of different experienced operators working by the same method and 

 upon the same material are frequently very large and often make all tlie 

 difference between rejected and accepted cement. Difl:erences in tensile 

 strength with neat cement of 40 to 60 per cent are not uncommon, while 

 for sand mortar they are much greater."'" ■' 



At present all standard specifications leave much to be desired. A 

 Government committee appointed to investigate the quality of a certain 

 brand of cement, after much consultation with engineers, chemists, 

 contractors and manufucturers, introduced its final report with these 

 remarks : 



"There are no standard specifications wliicli are I'egarded as absolutely correct. 

 All tests are approximations and must be interpreted in accordance with the 

 specifications in use, and with due regard to the purpose for wliicli tlie cement 

 will be used. 



"There is no practical difl'erence lietween the (|ualities and properties of a 

 rejected and of an accepted cement in the immediate vicinity of the limits set by 

 specifications." * 



It follows that the engineer may be in much doubt as to whether to 

 reject or accept a cement. 



"It must be recognized, however, that cement specifications are not for average 

 results, but are intended to cover the lowest limit wliich can be allowed in tlie 

 work and to provide for hick of uniformity in testing as well as in real (juallty." ■'' 



- Sabin, Louis Carlton: Cement and Concrete. Xew York (1905), 30. 



^Spalding, Frederick C, : Hydraulic Cement. New York (li)04). llo. 



^ Final report of cement investigation committee appointed by Executive 

 Order No. GO, 1907. — The C^overnment of the Philippine Isltmds. 



'Taylor and Thompson: Concrete. Plain and Reinforced. New York (1IJ07), 

 99. 



