196 
The Philippine Journal of Science 
1921 
2 gives test data on three Bataan sands, all of which are too 
fine for high-grade concrete work. 
BATANGAS 
Tests of concretes coming from Batangas Province are anom- 
alous. The two series of results obtained from 6-inch cubes 
made of concrete used in Obispo Bridge have practically the 
same values, 1,115 and 1,097 pounds per square inch, respec- 
tively, though the mixtures are apparently differently propor- 
tioned, the specimens being marked 1:2:4 and 1 : 3 : 6, re- 
spectively. It is impossible to explain these irregular results, on 
account of the scanty data available. This laboratory has made 
no test of Batangas sand or gravel. It is not improbable, how- 
ever, that these two series of specimens were made from the 
same batch of concrete, and were subsequently marked as shown 
in Table 8. Considering the age of the specimens in the first 
four series (57 days), these concretes must be classed as poor. 
The two tests of concrete from Matayuanoc Bridge indicate a 
very inferior product. 
BOHOL 
Disregarding the small differences in age of the concrete spec- 
imens made in Bohol, the compressive strengths average 777, 
843, and 507 pounds per square inch for the 1 : 2 : 4, 1 : 2.5 : 5, 
and 1:3:6 mixtures, respectively. The 1 : 2.5 : 5 mixtures 
average stronger than the richer 1:2:4. No information was 
sent to this laboratory concerning the source and kind of ag- 
gregate used in these specimens, but the debris remaining at 
the conclusion of the compression tests showed that the sand 
and gravel were of poor quality; the gravel was very soft, and 
some of it was covered with green algse which prevented good 
bonding. The sand was fine and dirty. All of these tests were 
made during 1910. Since that time the Bureau of Science has 
received no concrete specimens from Bohol. Three sands tested 
during 1917 and 1918 gave poor results; the grains are fine 
and soft afid contain much shell and coral debris. Mortars made 
from these inferior sands range in tensile strength from 
28 to 63 per cent of that of Ottawa sand mortar. It is clear 
that Bohol concrete aggregates are of inferior quality and unfit 
for high-grade concrete construction. 
BULACAN 
As a whole, concrete aggregates from Bulacan are better than 
the average, and they have given excellent results in the labo- 
ratory, though the field tests are too low. Pulilan and Bocaue 
