82 The Philippine Journal of Science 1914 



and desirable for the establishment of a Portland cement plant 

 in the Philippines. 



The present paper is a continuation of the work on this prob- 

 lem, special consideration being given to the results obtained 

 from the actual manufacture of Portland cement from some of 

 the raw materials. A thorough study of the commercial and 

 technical considerations involved in the economic production of 

 Portland cement from available local raw materials is a work 

 which will require years of careful study. 



A consideration of the physical properties is the first step in 

 the selection of cement raw material. If these are satisfactory, 

 the usual chemical analyses give data from which the compo- 

 sition of the raw cement mixture may be calculated and which 

 assist us to decide whether or not further investigation is neces- 

 sarj^ However, such data do not give the chemical combinations 

 of the constituents determined. Silica in the form of quartz 

 does not combine with limestone at a clinkering temperature 

 as readily as when it is in the form of a silicate. Although an 

 ultimate analysis gives the exact silica content of a material, 

 it does not specify whether it is in the crystalline, amorphous, 

 or combined form, a matter of great importance. 



A rational analysis may often aid in giving some idea as to 

 the nature of the principal ingredients; such as, clay substance, 

 feldspar, and quartz.* 



A large amount of experimental work has been done by 

 various investigators in their endeavors to work out a formula 

 to be used as a basis for the calculation of the raw cement 

 .mixture as mentioned in a previous paper.' Formulae serve 

 as a basis for the calculation of raw cement mixtures, but they 

 cannot be relied upon to furnish the particular proportion of 

 raw materials which will give the best results in any given 

 instance for they neglect the consideration of such factors as 

 the silica to alumina ratio; the amount of fluxing constituents, 

 such as ferric oxide, alkalies, etc. ; and the degree of fineness. 

 A mixture is made according to some formula, burned, the re- 

 sulting clinker ground, and the product tested according to the 



* In the case of materials other than kaolinitic clays, such data are 

 of comparatively little importance, because the method of calculating a 

 rational analysis is based on the composition of a typical orthoclase feldspar. 

 The method of rational analysis and determination of soluble silicates 

 suggested by Bleininger [Bidl. Ohio Geol. Sur. (1904), IV, 3, 67, 119] 

 is slightly different and preferable to the methods recommended in many 

 textbooks on quantitative analysis and ceramic work. 



' Cox, loc. cit., 214. 



