ASTM D4944-98
(Test Method)Standard Test Method for Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester Method
Standard Test Method for Field Determination of Water (Moisture) Content of Soil by the Calcium Carbide Gas Pressure Tester Method
SCOPE
1.1 This test method outlines procedures for determining the water (moisture) content of soil by chemical reaction using calcium carbide as a reagent to react with the available water in the soil producing a gas. A measurement is made of the gas pressure produced when a specified mass of wet or moist soil is placed in a testing device with an appropriate volume of reagent and mixed.
1.2 This test method is not intended as a replacement for Test Method D2216; but as a supplement when rapid results are required, when testing is done in field locations, or where an oven is not practical for use. Test Method D2216 is to be used as the test method to compare for accuracy checks and correction.
1.3 This test method is applicable for most soils. Calcium carbide, used as a reagent, reacts with water as it is mixed with the soil by shaking and agitating with the aid of steel balls in the apparatus. To produce accurate results, the reagent must react with all the water which is not chemically hydrated with soil minerals or compounds in the soil. Some highly plastic clay soils or other soils not friable enough to break up may not produce representative results because some of the water may be trapped inside soil clods or clumps which cannot come in contact with the reagent. There may be some soils containing certain compounds or chemicals that will react unpredictably with the reagent and give erroneous results. Any such problem will become evident as calibration or check tests with Test Method D2216 are made. Some soils containing compounds or minerals that dehydrate with heat (such as gypsum) which are to have special temperature control with Test Method D2216 may not be affected (dehydrated) in this test method.
1.4 This test method is limited to using calcium carbide moisture test equipment made for 20 g, or larger, soil specimens and to testing soil which contains particles no larger than the No. 4 Standard sieve size.
1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards statements, see Section 7.
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Designation: D 4944 – 98
Standard Test Method for
Field Determination of Water (Moisture) Content of Soil by
the Calcium Carbide Gas Pressure Tester Method
This standard is issued under the fixed designation D 4944; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope * 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method outlines procedures for determining the
responsibility of the user of this standard to establish appro-
water (moisture) content of soil by chemical reaction using
priate safety and health practices and determine the applica-
calcium carbide as a reagent to react with the available water
bility of regulatory limitations prior to use. For specific
in the soil producing a gas. A measurement is made of the gas
hazards statements, see Section 7.
pressure produced when a specified mass of wet or moist soil
is placed in a testing device with an appropriate volume of
2. Referenced Documents
reagent and mixed.
2.1 ASTM Standards:
1.2 This test method is not intended as a replacement for
D 653 Terminology Relating to Soil, Rock, and Contained
Test Method D 2216; but as a supplement when rapid results
Fluids
are required, when testing is done in field locations, or where
D 2216 Test Method for Laboratory Determination of Water
an oven is not practical for use. Test Method D 2216 is to be
(Moisture) Content of Soil and Rock
used as the test method to compare for accuracy checks and
E 11 Specification for Wire-Cloth Sieves for Testing Pur-
correction.
poses
1.3 This test method is applicable for most soils. Calcium
carbide, used as a reagent, reacts with water as it is mixed with
3. Terminology
the soil by shaking and agitating with the aid of steel balls in
3.1 Definitions of terms used in this test method can be
the apparatus. To produce accurate results, the reagent must
found in Terminology D 653.
react with all the water which is not chemically hydrated with
soil minerals or compounds in the soil. Some highly plastic
4. Summary of Test Method
clay soils or other soils not friable enough to break up may not
4.1 A measured volume of calcium carbide, in excess of that
produce representative results because some of the water may
needed to react with the water, is placed in the testing apparatus
be trapped inside soil clods or clumps which cannot come in
along with two steel balls and a representative specimen of soil
contact with the reagent. There may be some soils containing
having all particles smaller than the No. 4 sieve size and having
certain compounds or chemicals that will react unpredictably
a mass equal to that specified by the manufacturer of the
with the reagent and give erroneous results. Any such problem
instrument or equipment. The apparatus is shaken vigorously
will become evident as calibration or check tests with Test
in a rotating motion so the calcium carbide reagent can contact
Method D 2216 are made. Some soils containing compounds
all the available water in the soil. Acetylene gas is produced
or minerals that dehydrate with heat (such as gypsum) which
proportionally to the amount of available water present. The
are to have special temperature control with Test Method
apparent water content is read from a pressure gage on the
D 2216 may not be affected (dehydrated) in this test method.
apparatus calibrated to read in percent water content for the
1.4 This test method is limited to using calcium carbide
mass of soil specified.
moisture test equipment made for 20 g, or larger, soil speci-
4.2 A calibration curve is developed for each instrument and
mens and to testing soil which contains particles no larger than
each soil type by plotting the pressure gage reading and the
the No. 4 Standard sieve size.
water content determined from Test Method D 2216 using
representative specimens of the soil. The calibration curve is
This test method is under the jurisdiction of ASTM Committee D-18 on Soil
and Rock and is the direct responsibility of Subcommittee D18.08 on Special and
Construction Control Tests.
Current edition approved May 10, 1998. Published January 1999. Last previous Annual Book of ASTM Standards, Vol 04.08.
edition D 4944 – 89 (1994). Annual Book of ASTM Standards, Vol 14.02.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4944
used to determine a corrected water content value for subse- 6.5 Sieve, No. 4 (4.75 mm), conforming to the requirements
quent tests on the same type of soil. of Specification E 11.
6.6 Calcium Carbide Reagent, finely pulverized, of a grade
5. Significance and Use
that will readily combine with the available sample moisture
and is capable of producing acetylene gas in the amount of at
5.1 The water content of soil is used throughout geotechni-
cal engineering practice, both in the laboratory and in the field. least 0.14 cubic meters/kg (2.25 cu ft/lb). It is best to purchase
calcium carbide in small containers with air tight replaceable
Results are sometimes needed within a short time period and in
locations where it is not practical to install an oven or to lids, to store it in a dry place, to keep the lid on the container
at all times except when measuring out a portion for use in a
transport samples to an oven. This test method is used for these
occasions. test, and to use a complete container before opening a new one.
5.2 The results of this test have been used for field control Calcium carbide quality will deteriorate with time after it
of compacted embankments or other earth structures such as in becomes exposed to the atmosphere or any source of moisture.
the determination of water content for control of soil moisture Periodic purchase of a new supply is recommended.
and dry density within a specified range. 6.7 Miscellaneous Clothing or Safety Equipment, such as
5.3 This test method requires specimens consisting of soil goggles to protect the operator (see 7.2).
6.8 Equipment, as listed in Test Method D 2216, for per-
having all particles smaller than the No. 4 sieve size.
5.4 This test method may not be as accurate as other forming comparison tests to make calibration curves.
accepted methods such as Test Method D 2216. Inaccuracies
NOTE 1—Calibration kits are available from manufacturers for testing
may result because specimens are too small to properly
gasket leakage and for calibrating the gage. Periodic checks for gasket
represent the total soil, from clumps of soil not breaking up to
leakage are recommended. The gasket should be changed when leakage is
expose all the available water to the reagent and from other suspected. Gage calibration problems can usually be detected as the
instrument calibration curves are made (see Section 8). When the gage
inherent procedural, equipment or process inaccuracies. There-
needs adjusting, any good quality calibrating gage can be used.
fore, other methods may be more appropriate when highly
accurate results are required, or when the use of test results is
7. Safety Hazards
sensitive to minor variations in the values obtained.
7.1 When combined with water, the calcium carbide reagent
produces a highly flammable or explosive acetylene gas.
6. Apparatus
Testing should not be carried out in confined spaces or in the
6.1 Calcium Carbide Pressure Tester Set (including testing
vicinity of an open flame, embers or other source of heat that
chamber with attached pressure gage and a set of tared
can cause combustion. Care should be exercised when releas-
balances), for water content testing of specimens having a mass
ing the gas from the apparatus to direct it away from the body.
of at least 20 g, (10 g for the half measure required for wetter
Lighted cigarettes, hot objects or open flames are extremely
specimens). Testers that use a smaller mass are available, but
dangerous in the area of testing.
are considered too inaccurate for this standard. The testing
7.2 As an added precaution, the operator should use a dust
chamber with pressure gage and the balances are calibrated as
mask, clothing with long sleeves, gloves and goggles to keep
a set (see Section 8). A typical apparatus is shown in Fig. 1.
the reagent from irritating the eyes, respiratory system, or
6.2 Small Scoop, for measuring reagent.
hands and arms.
6.3 Two Steel Balls, (manufacturer supplied).
7.3 Attempts to test excessively wet soils or improper use of
6.4 Brush and Cloth, for cleaning and other incidental
the equipment, such as adding water to the testing chamber,
items.
could cause pressures to exceed the safe level for the apparatus.
This may cause damage to the equipment and an unsafe
condition for the operator.
7.4 Care should be taken not to dispose or place a significant
amount of the calcium carbide reagent where it may contact
water because it will produce an explosive gas.
8. Calibration
8.1 The manufacturer
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