PORTLxlND CEMENT TESTING. 

 Table XIII." 



151 



Condition. 



■ Mixture. 



T-day. 



28-day. 



3 months. 



1 year. 



2 years. 



3 years. 



All lumps 



No lumps 



Neat 



417 

 686 

 131 

 192 



589 

 756 

 244 

 330 



690 

 79S 

 826 

 380 



705 

 858 

 373 

 430 



739 

 8.57 

 372 

 449 



719 

 805 

 373 

 450 





All lumps 



Mortfir 











The disposal of these lumps then, especially those which, are too hard 

 to be broken up in the jJiocess of sieving, may exert considerable in- 

 fluence in the tensile strength ol^tained. If one tester pulverizes the 

 hard lumps and mixes this powder with the original sample, and the 

 other simply thrOM's them away, uniform results can not be expected. 



Should the cake be present in sufficient quantity to affect the tensile 

 strength appreciably, the person requesting the tests should be notified 

 of this condition. The presence of the cake may not be due to any 

 fault or carelessness on the manufacturer's part. Improper storage 

 while in the hands of the engineer or contractor may have caused it. 

 Instances are also on record in this laboratory where caking \vas induced 

 in the samples after they were taken from the stock. The samples were 

 taken during a rain storm and through carelessness and incompetency 

 on the part of the one handling them, they were allowed to get wet. 



If specifications are to guarantee uniform and just results in all 

 cases, the treatment of caked cement must be more fully described than 

 it has heretofore. 



INFLUENCE OF TEMl'EEATURE ON TIME OF SETTING. 



The general rule for all cements is that increase of temf)erature in- 

 creases the rate of setting. However, there is no fixed ratio between 

 the temperature increase and the accelerated setting produced by it. 

 The j)nblished reports of skilled operators vary in this respect, and L. 

 Tetmaier,^* after years of the most careful work was forced to admit 

 that "difEerent cements are differently influenced by alteration of tem- 

 perature * * * gj^d it is scarcely possible to deduce a general law 

 for even one class of cements." 



The results we have obtained on the setting time of various cements, 

 worked in the cold-storage room and at local temperature, have shown 

 that the samples, in this respect, could be divided into three classes : 



1. Slow setting cements, little afl:ected by a variation of temperature 

 from 20° to 30° C. 



" Griesenauer, Eng. News (1906), 55, 68. 

 "Soc. Ghem. Industry (1893), 12, 1036. 



