figure 15-27, three tests (called runs) were made, using
cans numbered 5, 10, and 1. Online D (weight of tare),
record the weight of each can. Note that although the
cans are identical in appearance, they vary slightly in
weight. Online A (weight of tare and wet soil), record
the weight of each can with wet contents. On line B
(weight of tare and dry soil), record the weight of each
can with contents after drying.
Online C, Ww (weight of water in the soil sample)
was obtained by subtracting (B) from (A). On line E,
Ws (weight of dry soil) was obtained by subtracting (D)
from (B).
The line labeled “water content, w,” shows the
results obtained by substituting the known values in the
following formula:
The average of these three values, or 12.7 percent, is the
value of w (percentage of moisture content) for the
sample.
Calcium Carbide Gas Pressure Method
This method uses a 26-g SPEEDY MOISTURE
TESTER to determine the moisture content of soils, fine
aggregates, sand, and clay. By using the SPEEDY
tester, the moisture content can be determined in the
laboratory or field in from 45 sec to 3 rein, depending
upon the material being tested. The tester operates on
the principle of a calcium carbide reagent (reactive
agent) being introduced into the free moisture of the soil
sample. The resulting chemical reaction creates a gas
that is contained in a sealed chamber, the pressure of
which can be measured with the built-in gas pressure
gauge.
APPARATUS.— The SPEEDY moisture test set
(fig. 15-28) includes the SPEEDY tester, a balance,
half-weight reagent, measuring scoop, brushes,
cleaning cloth, and two 1 1/4-in. steel balls.
PROCEDURE.— The procedure for determining
moisture content using the SPEEDY MOISTURE
TESTER is as follows:
1. Weigh a 26-g sample of soil.
2. Place the soil sample and two 1 1/4-in. steel balls
in the large chamber.
FIGURE REMOVED
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Figure 15-28.—SPEEDY moisture test set.
15-20
