TESTS ON CEMENT 



221 



TENSILE STRENGTH OF CEMENT BRIQUETS 



(Pounds per Square Inch) 



weakness rather than of superiority, because such a condition 

 is usually created by an excess of lime or of sulphates, either 

 of which may be injurious. Neat cement testing from 600 

 to 800 Ib. at 7 da. is generally the most desirable. 



SECONDARY TESTS 

 TESTS FOR TIME OF SETTING 



The time-oj '-setting test is made to determine whether or 

 not the cement will become hard at the time most desirable 

 in actual construction. If it begins to set too soon, the 

 crystallization of the particles will have begun before the 

 mortar or concrete is thoroughly tamped into place. If, 

 on the other hand, the cement sets too slowly the material 

 is more likely to suffer from exposure to heat, cold, dampness, 

 and frost; also, the progress of the work will be much delayed 

 on account of the greater interval required between different 

 sections, and the longer time the forms must be left up. 



In the setting of cements, two stages are recognized: 

 (1) When the paste begins to harden or to offer resistance to 



