44 
The Colorado Experiment Station. 
The statement that one part of cement mixed with three parts 
of sand makes a strong mortar, contemplates the use of coarse sharp 
sand. If the sand is fine, one part of cement to three parts of sand 
is not sufficient. One to three mixture of cement to sand is permis¬ 
sible only if the sand is suitable, but if the sand is other than the 
most desirable, the mixture must be made richer. This is regard¬ 
less of whether the full five parts of rock are present or not. 
Gravel .—Gravel should consist of aggregate varying in size 
from grains just too large to pass through a l/4-inch mesh screen 
up to rocks that can be passed through a 2-inch diameter ring. 
Bank Sand and Gravel .—Practically all builders will have oc¬ 
casion to use bank sand and gravel ready mixed. This must first 
be examined to see that it is free from dirt and vegetable matter. 
Before the proportion of cement can be determined the relation 
between the sand and gravel in the bank must be ascertained by 
passing it over a inch mesh screen set at an angle of 45 degrees. 
If a relation of three parts of sand to' five parts of gravel prevails 
quite uniformly throughout the bank and the sand is coarse, clean 
and sharp, a mixture of one part cement to five of the bank material 
may be used. If excess gravel is present the sand and gravel must 
be separated and the excess gravel discarded. 
Ordinarily the bank gravel contains an excess of sand. In this 
case the quantity of mixed sand and gravel to use may be determined 
as follows: 
Screen the sand from the gravel until three measures of sand 
are obtained. Then remix the gravel with these three measures of 
sand, and measure the two combined. This will represent the quan¬ 
tity of the bank material that may be mixed with one measure of 
cement. 
Kind of Measure .—The mason’s wheelbarrow which is filled 
level full with two sacks of cement is the most convenient measure 
to use in mixing materials. A cement barrel which holds just four 
sacks of cement may be used by knocking out the bottom and nail¬ 
ing boards on the sides for handles. A box without a bottom and 
with the sides extending to form handles may be easily constructed 
if a barrel is not obtainable. The size of this box may be deter¬ 
mined as follows: One sack of cement contains .95 cubic feet. It 
is desirable to mix two-sack batches, hence a box holding 1.9 cubic 
feet should be built. The following dimensions would give the ca¬ 
pacity 1 foot high by 1 foot wide by 1.9 feet long. If the mixed 
sand and gravel are suitable for a one to five mixture, this box will 
be filled five times with the sand and gravel and two sacks of cement 
will be spread over it upon the mixing platform. If the barrel is 
