200 The Philippine Journal of Science a 
COTABATO 
All of the concrete specimens coming from Cotabato were 
tested at ages ranging from 33 to 77 days, the majority being 
over 50 days old. Cotabato is located south of Manila a distance 
of several days by steamer, and transportation service between 
the two points is not always regular, so that considerable time 
is required for specimens to reach Manila. Delay during transit 
explains the age of the test pieces. Taking into consideration 
the time that elapsed between the date of manufacture and the 
date of rupture of these specimens, it will be seen that concrete 
from Cotabato ranges from poor to fair. The two 1 : 8 : 6 spec- 
imens made August 18, 1916, from concrete used in the con- 
struction of Cotabato Public Hospital, average 373 pounds per 
square inch, which is pretty low. lLinuac sand used in these 
cubes is fine-grained, as Table 2 shows, and one would expect 
a low-testing mortar; but two series of laboratory tests made at 
two different times, separated by an interval of two years, 
show that the 1 : 3 mortar is in both cases of practically the same 
strength as is standard Ottawa sand mortar. The unsatis- 
factory results obtained from this concrete are therefore not due 
to poor aggregate but are very likely due to incorrect propor- 
tioning of ingredients. 
ILOCOS NORTE 
Compressive strength results given by concrete specimens 
coming from Ilocos Norte are so extremely erratic and in- 
consistent that careless field work is clearly evident. The 
strength of the 1:2:4 test pieces made of concrete used in 
repair work on Gilbert Bridge show a startling variation. The 
minimum value is 714 pounds per square inch and the maximum 
3,111. Concrete used in Badoc School possesses more or less 
the same variability. The 1 :2.5:5 results vary from 434 to 
887 pounds per square inch. Results like these are of little value. 
By the exercise of due supervision during the proportioning 
and casting of concrete such freakish results can be obviated. 
ILOCOS SUR 
The few tests made of concrete cast in Ilocos Sur are charac- 
teristically irregular. Mixtures proportioned 1 : 2 : 4 and aged 
33 to 37 days gave average ultimate compressive strengths 
ranging between 777 and 1,384 pounds per square inch, and 
two test specimens from Vigan Central School, at the age of 
57 days, failed at even lower strengths, the average being 617 
pounds per square inch. Specimens made of the rich 1:1.5 :3 
