20 The Philippine Journal of Science i9i6 



especially near Guadalupe, this stone is unusually abundant. Large quan- 

 tities of it have been quarried and used in the construction of many churches 

 and other buildings and in the walls and fortresses of Manila. It is very 

 workable. Before it is distributed it is so soft that it can be quarried with 

 an axe, but it hardens rapidly on exposure. 



Philippine tuffs vary considerably in texture, color, density, 

 and chemical composition. Some are fine-grained and soft like 

 those quarried at Santa Mesa, Rizal, and at Tayawanak, Cavite ; 

 others are coarse-grained and hard like those taken out in the 

 vicinity of Meycauayan, Bulacan. The harder varieties are 

 preferred for construction, though much of the softer material 

 is used locally because it is cheaper. Cox^ reports a microscopic 

 examination of the tuff found in the vicinity of Manila and shows 

 it to be composed of (1) feldspar, (2) magnetite, (3) hornblende, 

 (4) quartz, (5) and a cementing material, largely composed of 

 oxide of iron. 



It was thought that the spalls and debris remaining after the 

 compression test on the Tayawanak tuff might possess poz- 

 zuolanic properties if finely ground and mixed with hydrated 

 lime. The problem is not a new one, but there seem to be no 

 published results on the properties of Philippine tuffs when 

 mixed with slaked lime. Such an investigation should be of 

 considerable local industrial value. Trass or pozzuolan cements 

 were used by the ancients and are still used to a considerable 

 extent in Europe. Vitruvius and Pliny both make mention of 

 their utility. Of late, considerable activity has been shown in 

 various circles regarding the efficacy of tuffs mixed with Port- 

 land cement when the latter is to be used in sea water.* Al- 

 though the tuff mixtures studied in this laboratory do not harden 

 to the same degree as does Portland cement, nevertheless they 

 could be used very advantageously under certain conditions as 

 a cheap and efficient building material. 



' Loc. cit. 



* Duryee, Puzzolan-Portland cement ; a suggestion for an improved 

 hydraulic cement. Eng. News (1910), 64, 596. 



Gebrauch von Trass bei Eisenbeton. Tonind.-Zeitg. (1913), 37, 1857. 



Poulsen, A., Diatomeerde als Puzzolane. Tonind.-Zeitg. (1913), 37, 1132. 

 (Mixing of Portland cement with ground diatomaceous earth.) 



Duryee, E., Further investigations of Puzzolan-Portland cements. Eng. 

 News (1912), 68, 297. 



Martin, Hr., Tiber den Wert von Trass Zuschlagen zum Zement und 

 Kalkmortel (1914), 13, 286-8, 298-306. 



Lippincott, J. B., Tufa cement as manufactured and used on the Los 

 Angeles aqueduct. Chem. Ab. (1911), 5, 1672; (1913), 7, 236. 



Jacobs, E., Use of trass in reinforced concrete. Ingenieur, 27, 134-8. 

 See Chem. Ab. (1913), 7, 237. 



