IX, A, 1 West and Cox: Philippine Cement Raw Materials 91 



Twelve per cent less calcium carbonate than demanded by the 

 formula would require 2.76 parts calcium carbonate to 1 part 

 of clay. The results of combining- pure limestone and Danao 

 clay according to this calculation are given in Table VI. 



Table VI. — Calculation of Danao clay-cement raw mixture. 







Individual constituents. 



Total. 



Silica 



(Si02). 



Alumina 



(Al203).» 



Iron 



oxide 



(FeaOs). 



Lime 

 (CaO). 



Magnesia 

 (MgO). 



1 

 Volatile 

 (CO2.H2O 

 etc.). 



Figures represent parts of the material by weigrht. 



Limestone 



276.00 

 100.00 









154.50 





121.40 

 10.31 



Clay 



.- - 

 58.35 



20.72 



7.85 



1.50 



1.97 





376. 00 

 131. 70 



68.35 



20.72 



7.85 



156.00 



1.97 



131.70 



Volatile 



Burned 













244.30 



58.35 



20.72 7.85 



156.00 



1.97 









Calculated composition in percentage. 



Mixture ^ 



Clinker 



100. 16 

 100.24 



15.62 



23.88 



5.51 

 8.48 



2. 09 41. 49 

 3.21 63.86 



0.52 

 0.81 



36.03 











■ Estimating all of the iron as ferric oxide. 



Silica to alumina (plus iron oxide) ratio in the mixture is 2.04. 



Lime to silica, alumina, and iron oxide ratio in the mixture is 1.8. • 



Cementation index of the mixture is 1.21. 



The mixture was burned to a hard, black clinker. The clinker 

 was ground and tested in the usual manner with the results 

 shown in Table VII. 



Table VII. — Physical examination of cement. 



Speci- 

 fic gra- 

 vity. 



Soundness. 



Initial set. 



Final set. 



Tensile strength in pounds per 

 square inch. 





Neat cement. 



1 cement : 3 sand. 



5 hours. 



28 days. 



7 days. 



28 days. 



7 days. 



28 days. 



3.25 



Sound - 



Sound . 



Hrs. milts. 

 1.35 



Hrs. mins. 

 2.5 



529 



' 608 



276 



402 



The above values represent the average of 6 determinations. 

 The high specific gravity is characteristic of a sound cement. 

 While the tensile strengths obtained are not high owing to the 



