Geology Reference
In-Depth Information
representative specimen of soil having all particles smaller than the No.
4 sieve size and having a mass equal to that specified by the manufac-
turer of the instrument or equipment. The apparatus is shaken vigor-
ously in a rotating motion so the calcium carbide reagent can contact all
the available water in the soil. Acetylene gas is produced proportionally
to the amount of available water present. The apparent water content is
read from a pressure gage on the apparatus calibrated to read in per-
cent water content for the mass of soil specified.
The actual step-by-step procedure is as follows (ASTM D 4944-04 [1]):
(1) Remove the cap from the testing chamber of the apparatus
and place the recommended amount of calcium carbide reagent
along with the two steel balls into the testing chamber. Most
equipment built to test 20-g samples requires approximately 22 g
of reagent (measured using the supplied scoop, which is filled
two times).
(2) Use the balance to obtain a specimen of soil that has a mass rec-
ommended for the equipment and contains particles smaller than
the No. 4 sieve size. One-half specimen size should be used when
the water content is expected to exceed the limits of the gage on the
gas pressure chamber or when it actually reaches or exceeds the
gage limit in any test [see (6)].
(3) Place the soil specimen in the testing chamber cap; then, with
the apparatus in the horizontal position, insert the cap in the test-
ing chamber and tighten the clamp to seal the cap to the unit. Take
care that no calcium carbide comes in contact with the soil until a
complete seal is achieved.
Note
—The soil specimen may be placed in the chamber with
the calcium carbide in the cap if desired.
(4) Raise the apparatus to the vertical (upright) position so that
the contents of the cap fall into the testing chamber. Strike the side
of the apparatus with an open hand to assure that all the material
falls out of the cap.
(5) Shake the apparatus vigorously with a rotating motion so
that the steel balls roll around the inside circumference and im-
pact a grinding effect on the soil and reagent. This motion also
prevents the steel balls from striking the orifice that leads to the
pressure gage. Shake the apparatus for at least 1 min for sands,
increasing the time for silts, and up to 3 min for clays. Some
highly plastic clay soils may take more than 3 min. Periodically
check the progress of the needle on the pressure gage dial. Allow
time for the needle to stabilize as the heat from the chemical
reaction is dissipated.
(6) When the pressure gage dial needle stops moving, read the dial
while holding the apparatus in the horizontal position. If the dial
goes to the limit of the gage, (1) through (6) should be repeated
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