IX, A, 1 West and Cox: Philippine Cement Raw Materials 95 



Table XII. — Physical examination of cement from volcanic tuff raw mixture 

 containing 5.22 per cent less pure limestone than required by the 

 formula. 



Fineness. 



Specific 

 gravity. 



Soundness. 



Initial set. 



Final set. 



Tensile strength in pounds 

 per square inch. 







Neat cement. 



1 cement: 

 3 sand. 



200 

 mesh. 



100 

 mesh. 



5 

 hours. 



28 

 days. 



7 

 days. 



28 

 days. 



7 

 days. 



28 

 days. 



95.0 



99.6 



3.16 



Sound - - 



Sound -- 



Hrs. rains. 

 30 



Hrs. mins. 

 40 



430 



620 



379 



423 



The data for the first mixture are very satisfactory. The 

 figures showing the tensile strength of neat cement for the 

 second mixture are somewhat lower. 



A few other mixtures containing still less calcium carbonate 

 were prepared ; namely, 9, 12, and 17 per cent less than required 

 by the formula, in order to gain a definite idea as to the most 

 favorable proportions in which to combine the tuft" and limestone. 

 The mortar strengths of the cement obtained from these are 

 recorded in Table XIII. 



Table XIII. — Tensile strength of cement from volcanic tuff raw mixtures. 



Per cent 



less 

 calcium 

 carbon- 

 ate than 

 required 

 by the 

 formula. 



Proportions (parts 

 by weight). 



Tensile strength 

 in pounds per 

 square inch. 



Tuff. 



Lime- 

 stone 

 (CaCOs). 



1 cement : 3 sand. 



7 days. 



28 days. 



a 



9 

 12 

 17 



1 

 1 

 1 



2.697 

 2.610 

 2.465 



226 

 214 

 169 



333 

 313 

 270 



From our experimental results it is evident that Portland 

 cement can be prepared from mixtures of volcanic tuff and pure 

 limestone. The mixture that contained 2.29 per cent less lime- 

 stone than is required by the formula gave the most favorable 

 results. 



One experiment was carried on in order to determine the 

 influence of mixing clay with volcanic tuff. Intimate mixtures 

 of 1 part of Danao clay with 2.83 parts of pure limestone (10 

 per cent less than required by the formula) and of volcanic tuff 



