146 The Philippine Journal of Science isu 



It is evident" that the well-burned clinkers could be mixed 

 with considerable of the underburned product, and yet, if 

 properly seasoned, produce Portland cement which would pass 

 all the requirements of our standard specilications. 



NATURAL (OR ROMAN) CEMENT 



In a previous publication of the Bureau of Science * we called 

 attention to the possibility that the present and near future 

 resources and the commercial and economic conditions of these 

 Islands might favor the manufacture of what may be called an 

 artificial natural, or Roman, ^ cement. 



Natural cements are largely used in America because of their 

 cheapness. They harden more rapidly in air or water than 

 hydraulic lime, but generally speaking they lack uniformity in 

 strength, setting properties, and constancy of volume to a much 

 greater extent than Portland cements. This is due largely to the 

 present universal practice of burning cement rock in set kilns 

 under which conditions considerable variations in chemical com- 

 position and both under- and overburning are unavoidable. 



To produce a more desirable cement of this class in the Phil- 

 ippines, we advocate the method of producing an artificial Roman 

 cement by blending ground calcareous and siliceous materials 

 in the proper proportion and then burning the mixture in a 

 rotary kiln at a temperature of about 1,000° C. By this method 

 the chemical composition and the degree of burning could be 

 uniformly regulated and a cement of definite physical properties 

 produced. It might not be a feasible method in countries where 

 the cost of the production of Portland cement is low, but the 

 high cost of imported coal and Portland cement in the Philippines 

 would overcome this objection and especially since local coals 

 could be utilized for burning the natural cement. 



We prepared and burned several of such artificial Roman 

 cement mixtures, and the results obtained showed conclusively 

 that the method could be adopted with good results. We had 

 time and opportunity to make only a very preliminary study of 

 the possibilities of the raw materials in this respect, but even so 

 obtained several cements which passed all of the requirements 

 of the American Society for Testing Materials for natural cement, 

 even though we used heavily clayed and, consequently, easily 

 burned mixtures. The data in Table XIV show that these 



' Cf. This Journal, Sec. A (1910), 5, 117-142. 



• This Journal, Sec. A (1913), 8, 135-195. 



' Bleining-er, A. V., Bull. Geol. Surv. Ohio (1904), 4, 186. 



