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TESTS ON CEMENT 



to dry out too quickly after being made. Pats must be kept 

 in a moist atmosphere while hardening, or these cracks, 

 indicative merely of careless manipulation will develop. 



Fig. 1 (c) shows cracks that are due to the expansion of the 

 cement. This condition is common in the air pats, and is 

 not indicative of injurious properties. Pats kept in water, 

 however, should not show these cracks. 



Fig. 1 (d) shows cracking of the glass plate to which the pat 

 is attached. This cracking is caused by expansion or con- 

 traction of the cement, combined with strong adhesion to the 

 glass. It rarely indicates injurious properties. 



Fig. 1 (e) illustrates blotching of the pats, the cause of 

 which should always be investigated by chemical analysis 

 or otherwise, which may or may not warrant the rejection of 

 the material. Slag cements or cements adulterated with slag 

 invariably show this blotching. 



