1、Standard Method of Test for Determination of Moisture in Soils by Means of a Calcium Carbide Gas Pressure Moisture Tester AASHTO Designation: T 217-14 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1a T 217-1 AASH
2、TO Standard Method of Test for Determination of Moisture in Soils by Means of a Calcium Carbide Gas Pressure Moisture Tester AASHTO Designation: T 217-14 1. SCOPE 1.1. This test method is intended to determine the moisture content of soils by means of a calcium carbide gas pressure moisture tester.
3、The manufacturers instructions shall be followed for the proper use of the equipment. 1.2. The following applies to all specified limits in this standard: For the purposes of determining conformance with these specifications, an observed value or a calculated value shall be rounded off “to the neare
4、st unit” in the last right-hand place of figures used in expressing the limiting value, in accordance with ASTM E29. Note 1This method shall not be used on granular materials having particles large enough to affect the accuracy of the testin general any appreciable amount retained on a 4.75-mm sieve
5、. The super 200 D tester is intended to be used to test aggregate. 1.3. The values stated in SI units are to be regarded as the standard. 1.4. Refer to R 16 for regulatory information for chemicals. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materia
6、ls R 16, Regulatory Information for Chemicals Used in AASHTO Tests T 265, Laboratory Determination of Moisture Content of Soils 2.2. ASTM Standard: E29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications 3. APPARATUS 3.1. Calcium Carbide Pressure
7、 Moisture TesterA chamber with attached pressure gauge for the water content of specimens having a mass of at least 20 g (Figure 1). 3.2. BalanceShall conform to M 231, Class G 2. 3.3. Steel BallsTwo 31.75-mm (1.25-in.) steel balls. 2015 by the American Association of State Highway and Transportatio
8、n Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 217-2 AASHTO 3.4. Cleaning brush and cloth. 3.5. ScoopFor measuring calcium carbide reagent. Figure 1Calcium Carbide Gas Pressure Moisture Meter 2015 by the American Association of State Highway and Transportation
9、Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 217-3 AASHTO 4. MATERIAL 4.1. Calcium carbide reagent. Note 2The calcium carbide must be finely pulverized and should be of a grade capable of producing acetylene gas in the amount of at least 0.14 m3/kg (2.25 ft3/lb
10、) of carbide. Note 3The shelf life of the calcium carbide reagent is limited, so it should be used according to the manufacturers recommendations. 5. PROCEDURE 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 u
11、sing 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 4Care 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 ma
12、nufacturer 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-sized
13、tester, place two 31.75-mm (1.25-in.) steel balls in the body of the tester with the sample. Note 5The 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 manufacturers instructions. Note 6Manufacturers instruct
14、ions shall be followed for the use of steel balls, particularly when testing sand. Note 7If 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 r
15、eading 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
16、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
17、 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 i
18、n the orifice leading to the pressure diaphragm. Note 8Shaking 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 gene
19、rated 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. 5.7. Record the sample mass and the dial reading. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. D
20、uplication is a violation of applicable law.TS-1a T 217-4 AASHTO 5.8. With the cap of the instrument pointed away from the operator, slowly release the gas pressure. Empty the pressure vessel and examine the material for lumps. If the sample is not completely pulverized, the test should be repeated
21、using a new sample. Clean the cap thoroughly of all carbide and soil before running another test. Note 9When removing the cap, care should be taken to point the instrument away from the operator to avoid breathing the fumes, and away from any potential source of ignition for the acetylene gas. 5.9.
22、The dial reading is the percent of moisture by wet mass and must be converted to dry mass. With the super 200 D tester, the dial reading is the percent of moisture by dry mass and no further calculation is required. 6. CALCULATION 6.1. The percentage of moisture by dry mass of the soil may be determ
23、ined from the correction curve (Figure 2). 6.2. A correction curve similar to Figure 2 is normally supplied with each moisture tester. Each moisture tester, however, should be checked for the accuracy of its gauge and for the accuracy of its correction curve. Figure 2Correction Curve for Moisture Te
24、ster Reading (Example OnlyUse the curve provided by the manufacturer with the specific apparatus, or a correction curve calibrated or extended for local soils at known moisture contents determined in accordance with Section 6.2.) 2015 by the American Association of State Highway and Transportation O
25、fficials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 217-5 AASHTO 6.2.1. The accuracy of the moisture tester gauge should be checked by using a calibration kit (available from the manufacturer), equipped with a standard gauge. In case of discrepancy, the gauge on the te
26、ster should be adjusted to conform with the standard gauge. 6.2.2. The accuracy of the correction curve should be checked by comparing curve-corrected moisture contents to moisture contents of locally prepared soils determined using T 265. In case of discrepancy, develop a new correction curve based
27、 on moisture contents determined from T 265. 6.2.3. The range of the factory-supplied or laboratory-determined curves may be extended by additional testing. Note 10It may be more convenient for field use of the apparatus to prepare a table of moisture tester readings versus oven-dry moisture content for the moisture tester. 6.3. Determine the percentage of moisture to the nearest 0.1 percent. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
