AASHTO T 217:2014 Standard Method of Test for Determination of Moisture in Soils by Means of a Calcium Carbide Gas Pressure Moisture Tester.
5.1. When using the 20- or 26-g tester, place three scoops (approximately 24 g) of calcium carbide in the cap of the moisture tester. When using the super 200 D tester to test aggregate, place six scoops (approximately 48 g) of calcium carbide in the cap of the moisture tester.
Note 4 —Care must be exercised to prevent the calcium carbide from coming into direct contact with water.
5.2. Weigh a sample of the exact mass specified by the manufacturer using the balance included with the instrument, and place the sample in the body of the tester and the calcium carbide reagent in the cap. Alternatively, the reagent may be placed in the body and the sample in the cap to facilitate cleanup after the test. When using the 20- or 26-g-sizcd tester, place two 31 .75-mm (1.25-in.) steel balls in the body of the tester with the sample.
Note 5 —The procedure for placing the soil specimen and calcium carbide reagent into the tester should be in accordance with Sections 5.1 and 5.2 or the manufacturer’s instructions.
Note 6—Manufacturer’s instructions shall be followed for the use of steel balls, particularly when testing sand.
Note 7—It is the moisture content of the sample exceeds the limit of the pressure gauge (12 percent moisture for aggregate tester or 20 percent moisture for soil tester), a one-half size sample must be used and the dial reading must be multiplied by 2. This proportional method is not directly applicable to the dry mass percent scale on the super 200 D tester.
5.3. With the pressure vessel in an approximately horizontal position, insert the cap in the pressure vessel and seal the unit by tightening the clamp, taking care that no carbide comes in contact with the soil until a complete seal is achieved.
5.4. Raise the moisture tester to a vertical position so the soil in the cap will fall into the pressure vessel.
5.5. Shake the instrument vigorously so all lumps will be broken up to permit the calcium carbide to react with all available free moisture. When steel balls are being used in the tester and when using the large tester to test aggregate, the instrument should be shaken with a rotating motion so the steel balls or aggregate will not damage the instrument or cause soil particles to become embedded in the orifice leading to the pressure diaphragm.
Note 8 —Shaking should continue for at least 60 s with granular soils and for up to 180 s for other soils so as to permit complete reaction between the calcium carbide and the free moisture. Time should be permitted to allow dissipation of the heat generated by the chemical reaction.
5.6. When the needle stops moving, read the dial while holding the instrument in a horizontal position at eye level.AASHTO T 217 pdf download.