73-1 M :w TORE BTATB Ml'sri'M 



iida may be greatly reduced, and a mixture of one 

 .•iit to Biz of Band may thua be made ae effective as a one to 

 three mixture with ordinary Band. Ii is evidenl that very many 

 careful will have to be made to determine the precise pro- 



portion sement and Band which will give a sand cement of 



tin' beet efficiency. There can be little doubt however that the 

 introduction of this new product will tend to increase the con- 

 sumption of Portland cement, Bince it will make it possible to use 

 Portland »mmon purposes at no greater cost than cheap 



hydraulic cement, and at the siiuc time to obtain greatly superior 

 .its. 



ecifications for Portland cement 

 In most countries where the Portland cement industry has 

 imed considerable importance, the engineering societies of 

 those countries have adopted a series of specifications to govern 

 the quality of Portland cement. The following abstracts of the 

 American, German, and Trench specifications are quoted from 

 Jameson. 1 



The testing of cement is not so simple a process as it is some- 

 times thought to be. No small degree of experience is necessary 

 before one can manipulate the materials so as to obtain even 

 approximately accurate results. 



The first tests of inexperienced, though intelligent and careful, 

 persons, are usually contradictory and inaccurate, and no amount 

 of experience can eliminate the variations introduced by the per- 

 sonal equations of the most conscientious observers. Many 

 things, apparently of minor importance, exert such a marked in- 

 fluence on the results that it is only by the greatest care in every 

 particular, aided by experience and intelligence, that trustworthy 



its can be made. 



The test for tensile strength on a sectional area of 1 square 

 inch is recommended, because, all things considered, it seems best 

 for general use. For the small briquet there is less danger of 

 air bubbles, the amount of material to be handled is smaller, and 

 the machine for breaking may be lighter and less costly. 



'1 he tensile test, if properly made, is a good, though not a per- 

 fect indication of the value of a cement. The time requisite for 

 making this test, whether applied to either the natural or the 



i Jameson. Portland cement, p. 08. 



