132 The Philippine Journal of Science 1921 
the concrete used in the particular structure concerned. Field 
specimens, referred to as stored in moist air, may be considered 
as having been sprinkled with water or as having been kept 
under moist sacking or buried in the ground. 
METHOD OF TESTING 
To insure uniform distribution of the load on the specimens 
made in the field it was found necessary to embed in plaster 
of Paris the rough ends bearing on the testing machine. The 
test pieces made in the laboratory were so smoothly finished 
that capping with plaster was unnecessary ; but a piece of card- 
board was interposed between the bearing surfaces and the table 
and crosshead of the machine. 
In embedding the ends of a specimen, plaster was thinly 
spread on a piece of cardboard resting upon a surface plate 
and one end of the test piece pressed in by hand so that plaster 
oozed out on all sides. After the plaster had set, the specimen 
was turned upside down and the other end forced into a thin 
layer spread on a piece of cardboard resting on a spherical bear- 
ing block. This time the specimen was pressed into the plaster 
by the testing machine, care being taken not to exceed an aver- 
age pressure of 30 pounds per square inch. After resting for 
at least twelve hours, the specimens were centered on a spherical 
bearing block that rests on the weighing table of the testing 
machine, and the test pieces together with the upper section of 
the spherical block were slowly rotated to insure uniform bear- 
ing, while the crosshead was brought down upon the specimen. 
The load was applied uniformly at the rate of about 0.5 milli- 
meter per minute. After rupture, the specimen was removed 
from the machine, and the fragments examined to determine the 
nature of the failure. If only the mortar had failed, the test 
was reported as a “mortar failure;” whereas, if considerable 
gravel or stone had been sheared or fractured in addition, the 
specimen was reported as a “gravel and mortar failure.” 
DISCUSSION OF RESULTS 
In Table 8 are recorded data obtained in testing 1,677 spec- 
imens of concrete. Most of these results were gotten from test 
pieces made in the field throughout the Archipelago; the rest 
were from specimens made in the materials testing laboratory 
of the Bureau of Science of aggregates sent by district engineers 
in charge of provincial building projects. 
ALBAY 
Examination of the data on compressive strength of concrete 
specimens listed under Albay, in Table 8, shows that the field 
