is ,2 King: Philippine Concrete and its Aggregates 131 
board. The mortar is now distributed on the gravel layer which 
has been spread on the mixing board to a depth that may range 
from 6 to 12 inches. Two or four men with shovels, stationed 
in pairs and facing each other, now proceed to mix the super- 
imposed blanket of mortar with the underlying layer of gravel 
in such a manner that the mortar is incorporated with only 
that portion of gravel lying directly underneath it so that the 
mass as a whole is not thoroughly intermingled, but is mixed 
sectionwise. In other words the two-layered mound of mortar 
and gravel is shoveled directly into buckets or wheelbarrows 
used for conveying the concrete to the structure, after each 
shovelful has been subjected to an average of four turns. Dur- 
ing this last mixing operation a man stands by with a hose or 
with pails of water to do the bidding of the men engaged in the 
mixing operation, who call for water as long as the mass offers 
decided resistance to the passage of the shovel on account of 
plasticity. They aim to get as wet a mix as possible in order 
to reduce their work to a minimum and to facilitate the placing 
of the concrete in the structure. The result is a soupy, non- 
uniform concrete, subject to segregation while being conveyed to 
its final resting place and while being placed. On account of 
the excessive amount of water added the concrete so mixed 
will have a low compressive strength, as tests have already 
shown. 
The concrete specimens cast in the field lacked the careful 
workmanship shown by the cylinders and cubes molded in the 
laboratory. In some few cases the honeycombed texture of the 
concrete test pieces made on the building site showed evidence 
of lack of tamping and spading. Their chief fault, however, 
was the irregular manner in which the cylinder ends had been 
finished so that it was necessary to embed them in plaster of 
Paris before they could be subjected to the compression test. 
Careless packing accounted for injuries sustained by some test 
pieces during transport from the building site to the laboratory, 
as a result of which no tests were possible. 
Data on the storage of concrete specimens fabricated in the 
field show considerable variation. On account of the distance 
between the building site and the laboratory and the irregular- 
ities of interisland communication, it was not always possible to 
receive the specimens in time to break them at the end of twenty- 
eight days. Results obtained from such belated test pieces lose 
some of their comparative value; but they have been included 
in this paper in order to convey some idea of the quality of 
