TESTING OF PORTLAND CEMENT. 



327 



171. Sampling. When a test or series of tests are to 

 be made on a particular delivery of cement, care should 

 be taken that the sample from which the test pieces are 

 prepared is a representative one. If the quantity is large, 

 samples should be taken from each or several of the sacks 

 or barrels, the sample being taken from well down in the 

 sack or barrel and not from the top. All these samples 

 are to be mixed together and the test specimens prepared 

 from a portion of the mixture. By doing this a fairly 

 representative sample should be obtained. 



FIG. 164. BAILEY'S AUTOMATIC TENSION TESTING MACHINE FOR CEMENT. 



In specifications for works in which Portland cement 

 is to be used it is usual to state that the cement must 

 satisfy certain requirements laid down in the specification. 

 It is with the intention of seeing whether the cement 

 supplied by the maker does satisfy the specified require- 

 ments that the following tests are undertaken. In this 

 country there is no attempt to make the requirements 

 absolutely uniform, each engineer having his own ideas as 

 to the necessary qualities. In other countries, notably 



