Determination of Moisture Content By Means of a Calcium Carbide Gas Pressure Moisture Tester


Determination of Moisture Content By Means of a Calcium Carbide Gas Pressure Moisture Tester


To determine the moisture content of soil by speedy moisture tester method


The water affects the density, shear strength, bulking and swelling of soil. Its determination is important to incorporate its effect on the performance of any engineering structure.


ASTM C566-97


Speedy moisture tester, Steel ball of 1.25 inch Dia, Brush for cleaning the tester, Scoop for measuring Calcium carbide reagent


The procedure for the test is as following: –

  1. Weigh 26 gm soil sample on the tarred scale and place it in the cap of the tester,
  2. Place two scoops of Calcium carbide and steel ball in the large chamber of the
  3. With the pressure vessel, seal the unity by tightening the
  4. Raise the tester to a vertical position so that the soil in the cap will fall into pressure
  5. Shake the Moisture tester vigorously so that all lumps are broken up to permit Cal carbide to react with all available free moisture. The instrument should be shaken with a rotating motion so that the steel balls will not damage the
  6. When the needle stop moving read the dial while holding the instrument in a horizontal position at eye
  7. Record the dial reading and release the gas

Observation and Data Collection

The only data in this test is the dial reading read from the moisture tester.

Dial Reading (DR) M.C=DRX100/ (100-DR)   (%)

Computation and Interpretation

The basic premises of Calcium Carbide gas in moisture tester is that free moisture in soil react with Calcium Carbide reagent to form a gas called Acetylene.

CaC2 + 2H2O ® Ca (OH)2 = C2H2.

The Acetylene gas is tapped within the tester register pressure on dial, which is calibrated, to read directly in percent of moisture by wet mass of soil. To calculate moisture content the following formula also is used.

Moisture Content =DRX100 / (100 – DR)           (%) Where: DR = Dial reading.


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