148 The Philippine Journal of Science i9i4 



2. The raw materials represented by coralline limestones 35, 

 37, and 39 and tuff 47 constitute the most desirable of the 

 available resources. This is especially true as, in addition to 

 their high merits with respect to manufacturing efficiency, their 

 use would reduce the cost of quarrying, transportation, and 

 grinding to a minimum. 



3. Proper mixtures of these two raw materials produce cements 

 which are comparatively high in silica and low in alumina, and 

 for best results the hydraulic modulus 



per cent CaO +per cent MgO 

 per cent SiOs+per cent R2O3 



should be kept within the higher (2 to 2.3) rather than the 

 lower (1.8 to 2) limits. Owing to the presence of a very 

 desirable quantity of fluxing materials, the high-limed mixtures 

 have ideal sintering properties and the use of less siliceous 

 materials is not desirable, much less necessary. 



4. Contrary to a somewhat general belief, it is not character- 

 istic of Portland cements as high in silica and low in alumina 

 as proper mixtures of these raw materials to harden too slowly. 

 On the contrary, they are very apt to be extremely quick setting 

 if the hydraulic modulus is low. 



5. These raw materials are capable of producing satisfactory, 

 artificial natural (or Roman) cement, and as the clay content 

 can be carried very high with good results the commercial 

 production could be accomplished at a minimum expense. 



Incidentally, this work demonstrates many important principles 

 involved in testing raw materials, and the results obtained add 

 corroborative evidence to our published observations and conclu- 

 sions concerning the physical and chemical properties of Portland 

 cement and specifications and methods for their purchase.^^ 



"Reibling, W. C, This Journal, Sec. A (1913), 8, 107-124. 



