90 The Philippine Journal of Science i9i4 



Ottawa-sand mortar for seven and twenty-eight days was 415 and 

 460 pounds, respectively, per square inch. 



A high-limed mixture requires a high-burning temperature, 

 and it is expedient to make the first trial burning with a low- 

 limed and heavily clayed mixture. It was the intention to follow 

 our work on low-limed mixtures with an investigation of those 

 high in lime, but we have been prevented from doing this by the 

 pressure of other work and so present such results as are 

 completed. 



CEBU RAW CEMENT MATERIALS 



Danao clay. — The suitability of this material for the manu- 

 facture of Portland cement has already been pointed out,'® and 

 it was desired to confirm this by a burning test. A composite 

 sample of specimens obtained from the Mount Licos region near 

 Danao, Cebu, was prepared by grinding and sifting to a fineness 

 of 120 mesh. No rational analyses were made as the material 

 was free from grit. In Table V is given the ultimate analysis 

 of this material. 



Table V. — Analysis of Danao clay. 



Constituent. Per cent. 



Silica (SiO:) 58.35 



Alumina (AI2O3) 20.72 



Iron (FeoO.) 7.85 



Lime (CaO) 1.47 



Magnesia (MgO) 1.97 



Volatile matter 10.31 



Total 100.67 



The calculation of the combining proportions of a pure lime- 

 stone and Danao clay cement mixture in accordance with the 

 formula (2.8CaOSi02 + 2CaO-R,0;) would be as follows: 



58.35 X 2.60 = 151.71 parts calcium oxide required by silica in 100 parts 



clay. 

 20.72 X 1.10 = 22.79 parts calcium oxide required by alumina in 100 parts 



clay. 

 7.85 X 0.70 = 5.49 parts calcium oxide required by ferric oxide in 100 parts 



clay. 

 179.99 parts calcium oxide required by 100 parts clay. 

 1.47 + (1.97 X 1.40) = 4.23 parts calcium oxide equivalent to calcium and 



magnesium in 100 parts clay. 

 179.99 — 4.23 = 175.76 parts calcium oxide to be added to 100 parts clay. 

 56 parts calcium oxide available in 100 parts pure calcium carbonate. 

 175.76/ 56 = 3.14 parts calcium carbonate required by 1 part clay. 



" Cox, he. cit., 218. 



