92 The Philippine Journal of Science 1914 



low lime content, they fulfill specifications." Indeed, it was not 

 anticipated that such a mixture would give a passable cement, 

 but a low-limed mixture was chosen to get conditions under 

 perfect control. No difficulty was experienced in working with 

 this material, and the experiment shows that Portland cement 

 can be manufactured satisfactorily from it. Higher tensile 

 strengths could be obtained by working out the most suitable 

 proportions in which to combine the raw materials. 



Volcanic tuff. — The chemical compositions of several samples 

 of Philippine tuffs have been published.'^ Andesitic volcanic 

 tuff borders the Pasig River near Guadalupe between Manila 

 and Laguna de Bay.^^ 



The ultimate analysis of this tuff indicates its adaptability 

 to the manufacture of cement, and we desired to confirm this 

 by actual manufacture. Its physical characteristics are some- 

 what variable; however, with proper care in preparing and 

 combining the raw mixture any difficulty arising from this source 

 could probably be eliminated. 



The sample of tuff used for these experiments was collected 

 from a bluff about 25 meters high on the shore of the Pasig 

 River. Specimens were taken at intervals of about 1 meter 

 beginning at the bottom and proceeding somewhat diagonally 

 to the top, so that the sample represents the different grades 

 of fine, coarse, and medium as they naturally occur in the deposit. 

 The sample was crushed, mixed, and ground. Table VIII gives 

 the analytical data pertaining to the composite sample used for 

 these experiments. 



" The standard Portland cement specifications adopted by the United 

 States Government and which apply to the Philippine Islands require. the 

 following fignJies for tensile strengths in pounds per square inch. 



Neat cement. \ 1 cement : 3 sand. 



7 days. 



28 days. 



7 days. • 28 days. 



500 



600 



200 275 



"Cox, Alvin J., This Journal, Sec. A (1908), 3, 404. 



"This is a water-laid formation. Adams [This Journal, Sec. A (1910), 

 5, 73] states, "It is usually clearly stratified and exhibits beds of variable 

 thickness. In places it grades into clayey, somewhat shaley beds and it 

 occasionally contains a conglomeratic phase, especially near the foothills of 

 the eastern cordillera. It is probable that a large part of the tuff deposits 

 was thrown out by the volcanoes of the southwestern region, but certainly 

 some sediments must have been derived from the adjacent cordillera." 



