328 TESTING OF PORTLAND CEMENT. 



France and Germany, the case is different, certain standard 

 rules being adhered to. 



FIG. 165. WKIGHINC SCALE AND CEMENT MOULDS. 



Speaking generally, the tests to which a sample of 

 Portland cement is subjected, are as follow : 



Tests for 



(a) Fineness. 



(6) Tensile strength. 



(c) Crushing strength. 



(d) Soundness. 



(e) Setting properties. 



In addition to these are also 



(/) Specific gravity, and 

 (g) Chemical composition. 



These various tests will now be described in detail. 



172. Fineness. The tendency is to grind cements 

 much finer at the present day than formerly, owning to the 

 fact that the finer a cement is the more thoroughly does it 

 unite with the water with which it is mixed, and the 

 more uniform is the composition. If a cement has been 

 underburned, that is to say, although it contains the 

 requisite amount of lime to satisfy the chemical conditions 

 necessary for proper combination, parts of it may not 

 have been burned to such a point as to have effected 

 complete chemical combination that is, small portions of 

 lime may exist in the cement as lime and these, often 

 isolated, portions of lime swell on admixture with water, 

 and so cause the cement to crack or "blow." Fine 



