PACINI, METAM0RPHI8M OF PORTLAND CEMENT 



199 



than the corresponding neat cement mixes, and the following series of 

 compressive tests was made : 



Table 11 



Effect of Clay upon Destructive Action of Eacess of Mixing Water 

 (Average of two tests at 28 days) 



Neat cement 



Cement, 10 per cent of which was 

 replaced by a fat clay (dried) 



Water, 

 per cent 



Compressive 

 strength, pounds 

 per square inch 



Water, 

 per cent 



Compressive 

 strength, pounds 

 per square inch 



50 

 75 

 100 

 150 

 200 

 500 



5782 

 3134 

 2273 

 1896 

 1381 

 514 



54 

 79 

 104 

 154 

 204 

 504 



1282 

 1328 

 2577 

 2156 

 1320 

 No strength 

 developed 



If the action of saline solutions upon cement is to accelerate the hy- 

 drolysis of the latter, it would appear that the destructive action of excess 

 water would be accelerated by the presence -therein of saline substances 

 in solution; also, it is legitimate to expect that the addition of clay- 

 restraining the hydrolysis due to excess water will in this case exert a. 

 similar influence. 



The following experiments, parallel to the foregoing ones, elaborate 

 this point: 



Table 12 



Effect of Clay upon accelerated destructive Action of Mixing Water Containing 

 5 per cent of Magnesium Sulphate 



(Average of two tests at 28 days) 



Neat cement 



Cement, 10 per cent of which was 

 replaced by a fat clay (dried) 



5 per cent solution 



Compressive 



5 percent solution 



Compressive 



of magnesium 



strength, pounds 



of magnesium 



strength, pounds 



sulphate, 



per square 



sulphate, 



per square 



per cent 



inch 



per cent 



inch 



50 



2196 



54 



2774 



75 



548 



79 



1608 



100 



1512 



104 



No strength 



150 



556 



154 



" " 



200 



No strength 



204 



(< (< 



500 



No strength 



504 



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