18,2 King: Philippine Concrete and its Aggregates 199 
work would certainly have resulted in more uniform results. 
Table 2 shows that two of the three sands submitted from Ca- 
vite are excellent, and the other is good. Suitable aggregates 
for concrete work are available in Cavite Province, so that with 
proper supervision high-testing concrete ought to be the rule. 
CEBU 
With the exception of the results obtained from Naga River 
Bridge specimens, the compressive strengths of Cebu concretes 
are excellent. Excluding the low Naga River Bridge results, 
and averaging the remaining field compressive strengths ob- 
tained from 1:2:4 concrete specimens having ages between 
26 and 28 days, a mean is obtained of 2,091 pounds per square 
inch, which exceeds by 37 pounds the average compressive 
strength of the 1:2:4 concrete specimens made at the Bureau 
of Science. The field-made 1:3:6 specimens average con- 
siderably higher than laboratory-made test pieces; these results 
are 1,229 and 1,032 pounds per square inch, respectively. How- 
ever, the extraordinarily high average result of 2,183 pounds 
per square inch, gotten from the four 1:3:6 field specimens 
representing concrete that was used in the west abutment of 
Magallanes Bridge, October 15, 1911, should be viewed with 
suspicion. The probability that the specimens were mislabeled 
(1 : 3 : 6 for 1 : 2 : 4) , or that there was an accidental increase 
in the quantity of cement used, should not be excluded. By 
ignoring this doubtful high result, the average of the remaining 
1:3:6 specimens aged 26 to 27 days is reduced to 753 pounds 
per square inch, which compares favorably with the average of 
1,032 pounds obtained from the laboratory-made specimens. 
It is interesting to note the great divergency in the com- 
pressive strengths of two lots of specimens coming from Sibonga 
Bridge. Both series of results were obtained from 1:3:6 con- 
crete of practically the same age and made of the same aggregate, 
yet one average result is twice that of the other ; the compressive 
strengths are 1,002 and 503 pounds per square inch, respectively. 
Such discrepancies are not uncommon in the data published in 
this paper and detract not a little from the reliance that can 
be placed on these tests. As Table 2 shows, tests of sands from 
Cebu are fragmentary; no compression tests of mortars were 
made, but the tensile strength of 1 : 3 mixture shows that Ma- 
nanga River sand is an excellent concrete aggregate, whereas 
the other three are of only fair quality. 
