130 The Philippine Journal of Science i9i4 



one-half of these could not have produced a slow-setting paste 

 before they were packed, unless regauging had taken place to 

 a considerable extent during the process of mixing. 



We also disputed the correctness of the assumption that the 

 cements obtained from these raw materials would set and harden 

 slowly, because the value of the ratio of silica to alumina was 

 high. Apparently many experts believe that the early harden- 

 ing properties of Portland cement are due to the aluminates. 

 If this were true, we could not account for the rapid development 

 of great strength and quick-setting properties of many well- 

 burned, highly siliceous Portland cements which have come under 

 observation. Our own extensive researches verify the work of 

 Dr. 0. Schott ' that the quick-hardening compounds of Portland 

 cement are formed at a high temperature and that with the 

 silicates the strength increases as the lime increases while with 

 the aluminates the opposite is true; and as the high silicates 

 and the low aluminates require the greatest heat it is evident 

 that high temperatures produce high strength. 



We further expressed the opinion that a high silica cement 

 should carry more calcareous material than one with less silica 

 and more alumina and that in several instances the hydraulic 

 moduli of mixtures prepared in the United States were too 

 low. We realized that an increase in the calcareous constituents 

 would raise the clinkering temperature, but believed that there 

 was sufficient iron oxide in the raw materials to permit higher 

 liming. For the same reasons, the use of less siliceous materials 

 did not seem desirable, much less, necessary. 



While many of the problems involved in the successful and 

 economic manufacture of Portland cement cannot be solved by 

 laboratory experiments, we believe that an investigation such 

 as is outlined and described in the following pages will establish 

 the relative merits of different raw materials and point out 

 the most important of the conditions of manufacture which will 

 produce the most desirable results. 



EXPERIMENTAL WORK 



The geology, field relations, and physical characteristics of the 

 raw materials are discussed by Mr. Pratt on pages 151 to 161. 

 The chemical characteristics of each of the 8 samples of raw 

 materials examined are made apparently by the data in Table I. 



"Cement & Eng. News (1910), 22, Nos. 9-13. 



