5.1 The specific gravity of soil solids is used in calculating the phase relationships of soils, such as void ratio and degree of saturation.

5.1.1 The specific gravity of soil solids is used to calculate the density of the soil solids. This is done by multiplying the specific gravity by the density of water at 20°C. The soil solids density is nearly independent of temperature.

5.2 The term soil solids is typically assumed to mean naturally occurring mineral particles or soil like particles that are not readily soluble in water. Therefore, the specific gravity of soil solids containing extraneous matter, such as cement, lime, and the like, water-soluble matter, such as sodium chloride, and soils containing matter with a specific gravity less than one, typically require special treatment (see Note 2) or a qualified definition of their specific gravity.

Note 2: For some soils containing a significant fraction of organic matter, kerosene is a better wetting agent than water and may be used in place of test water for oven-dried specimens. Kerosene is a flammable liquid that must be used with extreme caution. This standard should not be used when using kerosene as the test fluid.

5.3 The balances, pycnometer sizes, and specimen masses are specified to obtain test results reportable to four significant digits.

Note 3: The quality of the result produced by these test methods is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of these test methods are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.

These test methods cover the determination of the specific gravity of soil solids passing a sieve by means of a water pycnometer. Soil solids for these test methods do not include solids which can be altered by these methods, contaminated with a substance that prohibits the use of these methods, or are highly organic soil solids, such as fibrous matter which floats in water. Procedures for moist specimens such as organic soils, highly plastic fine grained soils, tropical soils, and soils containing halloysite and oven-dry specimens are provided. The apparatus is comprised of water pycnometer which shall be a stoppered flask, stoppered iodine flask, or volumetric flask; balance; drying oven; thermometer; dessicator; a system for entrapped air removal which shall be a hot plate or Bunsen burner or a vacuum pump or water aspirator; insulated container; non-corrosive smooth surface funnel; pycnometer filling tube with lateral vents; sieve; and blender with mixing blades. The specific gravity of the soil solids at the test temperature shall be calculated from the density of the soil solids and the density of water at the test temperature or from the mass of the oven dry soil solids; mass of pycnometer, water, and soil solids at the test temperature; and mass of the pycnometer and water at the test temperature. Precision and bias shall be determined to judge for the acceptability of the test results.

1.1 These test methods cover the determination of the specific gravity of soil solids that pass the ³/₈-in. (9.5-mm) or smaller sieve by means of the water displacement method. When the total sample contains larger particles, it is separated into a coarser and finer portion using a ³/₈-in. (9.5-mm) or No. 4 (4.75-mm) or finer sieve. Separation on the No. 4 sieve is the referee method. Test Method C127 shall be used to obtain the specific gravity of the coarser portion. The D854 test methods shall be used to obtain the specific gravity of the finer portion. The total sample specific gravity is computed from the two portions as described in 12.5.

1.1.1 These test methods do not apply to solids which can be altered by these methods, contaminated with a substance that prohibits the use of these methods, or are highly organic, such as fibrous matter which floats in water (see Note 1).

Note 1: Test Method D5550 may be used to determine the specific gravity of soil solids having solids, which readily dissolve in water or float in water, or where it is impracticable to use water.

1.2 This standard provides two methods for performing the specific gravity test. The method to be used shall be specified by the requesting authority, except when testing the types of soils listed in 1.2.1.

1.2.1 Method A—Procedure for Moist Specimens, described in 11.1. This procedure is the preferred method. Method A shall be used for organic soils; highly plastic, fine-grained soils; tropical soils; and soils containing halloysite.

1.2.2 Method B—Procedure for Oven-Dry Specimens, described in 11.2. This procedure requires less time and may be used for clean sands.

1.3 Units—The values stated in SI units are to be regarded as standard, except the sieve designations. The sieve designations are identified using the “alternative” system in accordance with Practice E11, such as 3-in. and No. 200, instead of the “standard” designation of 75-mm and 75-µm, respectively. Reporting of test results in units other than SI shall not be regarded as non-conformance with this test method. The use of balances or scales recording pounds of mass (lbm) shall not be regarded as nonconformance with this standard.

1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026, unless superseded by this test method.

1.4.1 The procedures used to specify how data are collected/recorded and calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of these test methods to consider significant digits used in analysis methods for engineering design.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Glassware under vacuum has the potential for implosion. Proper personal protective equipment shall be used at all times. See Section 8.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.