214 The Philippine Journal of Science 1921 
is available with respect to the proportions used in the 58-day 
specimens made of concrete employed in the construction of the 
Atimonan Trade School. These particular test pieces give an 
extraordinary variation in compressive strength; the minimum 
and maximum values are 329 and 1,530 pounds, respectively. 
Concrete from Dumaca Bridge proportioned 1 : 3 : 6 gives fair 
values which average 573 pounds per square inch for specimens 
aged 28 or 29 days. Only one Tayabas sand was tested. It came 
from pit No. 1, Sariaya-Muntig River, and as Table 2 shows 
1 : 3 mortar made therefrom gives excellent tensile and com- 
pressive strengths, which are appreciably higher than the cor-. 
responding ones obtained from Ottawa sand mortar test 
specimens. 
ZAMBALES 
Compressive strengths of concretes coming from Zambales 
Province are characterized by low, erratic averages. The spe- 
cimens made of 1 : 2 : 4 concrete aged 28 days and used in the 
construction of Yamot Bridge give strengths that vary from 
390 to 1,067 pounds per square inch. Test specimens made from 
1 : 2 : 4 concrete employed in Candelaria Bridge give slightly 
better results than the 28-day cylinders averaging 822 pounds 
per square inch, and the 40 to 43-day cylinders averaging 1,101. 
The sands available for concrete construction in Zambales are 
very good as a whole, and some are excellent. All of them 
are clean and composed of hard grains, but the granulometric 
analysis in most cases shows a preponderance of fine grains. 
_ Nevertheless, the compressive strength of some of the 1 : 8 
mortar specimens exceeds that shown by the corresponding 
Ottawa sand mortar cylinders. Test specimens made of sand 
from Lauis River give an average compressive strength at 28 
days of 3,120 pounds per square inch, which is about 1.2 times 
that shown by Ottawa sand mortar test pieces. This sand ap- 
parently was used in the construction of Yamot Bridge, but 
the field tests of concrete containing it are far from satis- 
factory. Taking into consideration the good qualities possessed 
by Zambales sands in general, high-testing concrete ought to be 
the rule. 
ZAMBOANGA 
All of the test specimens coming from Zamboanga were made 
of the 1 : 2 : 4 concrete used in the construction of the Zamboanga 
Waterworks. The compressive strengths are fair. They are 
also uniform, which indicates a uniform method of measuring 
the cement and aggregates. The minimum and maximum re- 
