Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester - Soil Properties: Testing, Measurement, and Evaluation - page 194

using a new specimen having a mass half as large as the recom-
mended specimen. When a half size specimen is used, the final dial
reading is multiplied by two for use with the calibration curve.

(7) Record the final pressure gage dial reading and use the appro-
priate calibration curve to determine the corrected water content in
percent of dry mass of soil and record.

(8) With the cap of the testing chamber pointed away from the oper-
ator, slowly release the gas pressure (see “Safety Hazards” section).
Empty the chamber and examine the specimen for lumps. If the ma-
terial is not completely pulverized, the test should be repeated using
a new specimen.

(9) Clean the testing chamber and cap with a brush or cloth and
allow the apparatus to cool before performing another test. Re-
peated tests can cause the apparatus to heat up, which will affect
the results of the test. The apparatus should be at about the same
temperature as it was during calibration (determined by touch).
This may require warming the instrument up to calibration tem-
perature before use when the temperature is cold.

(10) Discard the specimen where it will not contact water and pro-
duce an explosive gas. It is recommended that the specimen soil not
be used for further testing as it is contaminated with the reagent.

The only datum recorded in this test is the dial reading from the mois-
ture tester.

DATA

The percent of moisture by dry weight of soil may be determined from
the observed dial reading of the calcium carbide moisture tester by
using a calibration curve such as the one given in Figure 13-2.

CALCULATIONS

The calcium carbide gas pressure tester provides a quick, simple means of
finding the moisture content of soil. It is useful when rapid results are
needed, when testing is done in field locations, and when an oven (or mi-
crowave) is not available. It is particularly useful for field determinations
of moisture contents in conjunction with field compaction testing. This test
method is not, however, intended as a replacement for the “oven method”
(ASTM D 2216; see Chapter 4); in fact, Method D 2216 is to be used as the
test method to compare for accuracy of the calcium carbide tester.
Interestingly, this tester can be used to determine the moisture con-
tent of many materials other than soil (e.g., ores, solid fuels, ash, oil, tex-
tiles, paper, ceramics, cosmetics, processed food) in many other fields
(e.g., agriculture, brewing, chemicals, construction, pharmaceuticals,
waste disposal).

SUMMARY

REFERENCE

[1] ASTM, 2007 Annual Book of ASTM Standards , West Conshohocken, PA,

2007. Copyright, American Society for Testing and Materials, 100 Barr
Harbor Drive, West Conshohocken, PA 19428-2959. Reprinted with per-
mission.