18, 2 King: Philippine Concrete and its Aggregates 133 
tests are fair. When classified into series and averaged the 
results are consistent in that the mixtures poorest in cement 
average weakest, and those richest in cement average strongest. 
Disregarding the slight differences in age of the various field 
specimens, it will be seen that the 1 : 3 : 6 mixtures average 607 
pounds per square inch; the 1:2:5 mixtures, 923; and the 
1:2:4 mixtures, 1,068. The corresponding results obtained 
from laboratory-made specimens average about twice as high; 
thus the results given by the 1:2:4 concrete made at the 
Bureau of Science average 2,578 pounds per square inch, and 
a single laboratory-made specimen of 1:3 :6 concrete has a 
compressive strength of 1,046 pounds per square inch; these 
results are 2.5 and 1.7 times as great as the respective average 
field results. Table 2 gives the tests of four sands from Albay, 
all of which are satisfactory and compare favorably with those 
of Ottawa sand. In fact, Quinale River sand mortar gives a 
higher compressive strength at the end of 28 days than does 
standard Ottawa sand mortar. 
ANTIQUE 
The results obtained from concrete specimens made in An- 
tique are interesting examples of extreme aberrancy and are 
somewhat puzzling, considering the lack of information on the 
aggregates used. No tests have been made of Antique sands 
or gravels, and even the origin of the aggregates which were 
used in making the 1 : 2:4 mixtures that gave the extraordi- 
narily low average compressive strengths of 233 and 281 pounds 
per square inch is not known. The specimens cast of similar 
concrete and used in constructing Ipil Bridge, though younger, 
gave the good average strength value of 1,334 pounds per square 
inch. The results are clearly freakish and indicative of care- 
less field procedure. A preliminary laboratory test of available 
aggregates for the purpose of choosing the most suitable sand 
and gravel, coupled with careful field work, would have obviated 
such irregular results. 
BATAAN 
The compressive strengths of concrete recorded under Bataan 
were all obtained from specimens made in the materials testing 
laboratory of the Bureau of Science. The results are only fair. 
Specimens made of 1 : 2: 4 concrete and aged 28 days average 
only 1,723 pounds per square inch, and 1:3 :6 test pieces of 
the same age average 889. These low compressive strength 
values are entirely due to the very fine beach sands used. Table 
