210 The Philippine Journal of Science 1921 
was tested in the laboratory and the average compressive 
strength at 28 days given by the 1 : 3 mortar specimens is very 
good, being 91 per cent of that given by test pieces made of 
standard Ottawa sand mortar. 
PALAWAN 
No concrete test specimens have been received from Palawan 
Province, and only three laboratory-made specimens were tested; 
these were made of Coron beach sand and gravel. Although 
the average compressive strength of the 1 :3 mortar cylinders 
made of Coron beach sand is less than half of that shown by the 
1:3 Ottawa sand test pieces, the compressive strength (2,443 
pounds per square inch) of the 1:2 :4 concrete made of the 
sand and gravel from Coron beach, used in connection with the 
construction of the Coron wharf, is very good. Inspection of 
the results in Table 2 obtained in testing Coron beach sands 
shows that whereas the average compressive strength of the 
1:3 mortar specimens is 92 per cent of that given by the Ot- 
tawa sand test pieces, the tensile strength of the 1:3 Coron 
sand briquettes is only 44 per cent of that given by Ottawa 
sand briquettes, the age in all cases being 28 days. These re- 
sults show that the time-honored tensile-strength test of Port- 
land cement mortars is not always a true guide as to what may be 
expected from the same mortar when subjected to compression. 
PAMPANGA 
All results recorded under Pampanga in Table 8 were obtained 
from specimens made at the Bureau of Science of aggregates 
proposed for buildings at Camp Stotsenberg. All of the mix- 
tures are 1:2:4 and give a mean compressive strength of 
1,925 pounds per square inch, which is a little better than fair. 
Table 2 shows that the sand coming from Camp Stotsenberg 
is fine, and 1 :3 mortar made therefrom gives only 75 per cent 
of the tensile strength of the 1 : 3 mortar briquettes made from 
standard Army sand composed of crushed quartz. 
PANGASINAN 
Very good results were obtained from concrete test specimens 
coming from Pangasinan. The values given by the 1:2:4 
mixtures are uniform and average 1,628 pounds per square inch; 
those of cubes made of 1 : 2.5 : 5 concrete are erratic and aver- 
age 1,238 pounds per square inch. The marked variability of 
strength in this series from a minimum of 730 to a maximum 
of 1,717 pounds per square inch is probably due to difference 
