212 
The Philippine Journal of Science 
1921 
siderably older than 28 days at the time of the test. These 
irregularities in age, as in most of the other cases, were caused 
by delays in shipping the specimens to the testing laboratory 
in Manila. On acount of transportation difficulties it is not 
always possible to send specimens from unfavorably located 
districts promptly and have them in Manila in time for the 
28-day test. 
The 1:2:4 specimens aged 62 to 69 days average 1,298 
pounds per square inch, and those aged from 74 to 91 days, 
only 913. These results are poor and are less than the value 
that a good grade of 1 : 2 : 4 concrete should give at 28 days. 
Some of the poor results obtained from Samar concrete are 
undoubtedly due to the use of the very fine beach sands charac- 
teristic of that province. Of the three sands tested two gave 
very unfavorable results, as Table 2 shows, and they should not 
be used as concrete aggregates. The compressive strength of 
the 1 : 3 mortar specimens in both of these instances is less 
than half that given by the corresponding Ottawa sand mortar 
test pieces. The third sand, which also came from the beach 
and which was tested November 24, 1914, although it gives 
excellent mortar strength values, shows a deficiency of fine 
grains and, therefore, makes a porous, permeable mortar that 
would allow the ingress of disintegrating substances. 
SORSOGON 
Although all of the specimens coming from Sorsogon were 
made of Salog River aggregate, and all, with the exception of 
those cast on November 9 and 15, 1915, were made of the same 
brand of cement, the compressive strengths show marked varia- 
tion, the highest value being more than twice that of the lowest. 
The maximum and minimum are 961 and 432 pounds per square 
inch, respectively, and the average for 1:2:4 specimens aged 
29 to 33 days is 668 pounds per square inch. The mean com- 
pressive strength is low and indicates a poor grade of concrete. 
Older specimens however show improvement in strength; the 
four test pieces aged 51 to 58 days average 974 pounds per 
square inch. 
SURIGAO 
Test pieces coming from Surigao were all made from 1:2:4 
concrete used in the construction of Bilang-bilang wharf. The 
results are all poor. Specimens aged 21 to 29 days are fairly 
uniform in strength and average 602 pounds per square inch. 
The results given by the oldest, aged 35 to 37 days, are anomal- 
ous in that the older specimens are weaker than the younger 
