22 The Philippine Journal of Science i9i6 



When mixed with lime, the tuff exhibits very marked 

 hydraulic properties, developing considerably higher compressive 

 strength per unit area than the original tuff blocks as taken out 

 of the quarry. The tensile strength of the mortar at the 90- 

 and 180-day periods is greater than that of the corresponding 

 neat briquettes and equals the strength of the average Portland 

 cement-mortar briquettes tested in the Bureau of Science. The 

 results show that the tuff possesses well-defined pozzuolanic 

 properties. The quarry where this tuff was obtained unfortun- 

 ately has little economic importance at present because it is 

 situated in the interior of Cavite Province at a considerable 

 distance from both rail and water transportation. It was, there- 

 fore, decided to use a different tuff in making the more extensive 

 tests. The tuff obtained near Meycauayan, Bulacan Province, 

 was finally chosen because of the favorable location of the quarry 

 and the superior quality of the material. 



On April 6, 1915, I made a trip to the quarry at the barrio 

 of Ligtong on Ligtong River, about twenty minutes' walk from 

 the Meycauayan railroad station. The quarry, known as 'Ti- 

 bagan," is owned by Francisco Carreon. The Tibagan is one 

 of the oldest tuff quarries near Manila, having been worked 

 during the early Spanish period. It furnishes the hardest and 

 most durable tuff found on the Manila market. It is of interest 

 to note that the quality of the tuff in this one quarry is variable ; 

 some pits produce a much softer stone than adjacent ones and 

 are for that reason preferred by the workmen, since quarrying 

 is easier. Large quantities of debris resulting from the dressing 

 and quarrying of the tuff are strewn about; these served as the 

 source of the sample secured for this investigation. 



EXAMINATION OF THE MEYCAUAYAN TUFF 



A megascopic examination of the Meycauayan tuff shows it 

 to be constituted of comparatively large, irregular fragments of 

 igneous material embedded in a fine-grained matrix. It may 

 be designated as a water-laid agglomerate. Most of the coarser 

 components are volcanic ejecta. These cemented ejecta consist 

 of sharp fragments of basalt, coarse pieces of pumice, volcanic 

 glass, and scoria. The tuff is gray, with a bluish green cast. 

 It is fairly resistant, but is easily scratched with the sharp point 

 of a pocket knife. 



An analysis of the tuff is given in Table III. 



