170 



The Philippine Journal of Science 



1914 



with the highest cementation index at a low temperature and 

 vice versa. However, there was no opportunity to make other 

 than a rather preliminary examination of the possibilities of 

 these raw materials in the artificial process of manufacture. 



The burned bricks were soft and easy to grind. They were 

 aerated for twenty-four hours in the laboratory, pulverized, and 

 tested for fineness, specific gravity, soundness in steam, and 

 setting properties. The results obtained are recorded in Table VI. 



Table VI. — Physical characteristics of the four artificial Roman cements' 



" Tested according to the 1912 United States Specification for Portland cement. 

 '' The figures in parenthesis give the percentage of water required for a paste of normal 

 consistency. 



Standard specifications do not require that natural cements 

 pass the accelerated tests for soundness, but all of these cements 

 remained sound when subjected to the regular steaming test 

 for Portland cements. The nonplastered, nonseasoned cements 

 failed to harden sufficiently within twelve hours to bear the 

 weight of the heavy Gilmore needle without showing the mark 

 of the point. On the other hand, all of the cements gained their 

 final set in less than ten hours, which must be considered very 

 satisfactory for natural cements tested by the Gilmore method." 



The setting properties of these cements were again tested 

 after they had aerated for eighteen hours, spread out on paper 

 in layers about 1 centimeter thick. The results obtained are 

 given in Table VII. 



As anticipated, seasoning had the desired effect of retarding 

 the initial set and quickening the final set, and all of the plastered 

 cements set in a very satisfactory manner. 



'Cf. Reibling, W. C, and Salinger, L. A., This Journal, Sec. A (1908), 

 3, 137-185. 



