Significance and Use
5.1 Material finer than the 75-μm (No. 200) sieve can be separated from larger particles or soil aggregations can be broken down much more efficiently and completely by wet sieving than with dry sieving. Therefore, when accurate determinations of material finer than a 75-μm (No. 200) sieve are desired, these test methods are used on the test specimen prior to dry sieving, or as a determination of the percent of material that is finer than a 75-μm (No. 200) sieve. Usually the additional amount of material finer than a 75-μm (No. 200) sieve obtained in the dry sieving process is a small amount. If it is large, the efficiency of the washing operation should be checked, as it could be an indication of degradation of the soil (see ).
5.2 Method A shall be used with non-cohesive soils containing fine material with little or no plasticity. The specimen is soaked in water to facilitate the separation of the fine and coarse fractions prior to washing through the 75-μm (No. 200) sieve.
5.3 Method B shall be used with soils, particularly clayey soils, where the fine material demonstrates plastic behavior and tends to adhere to the larger particles. To provide adequate fine grain dispersal, it is necessary to soak the specimen in a dispersing solution prior to washing through the 75-μm (No. 200) sieve.
5.4 To facilitate determination of which method to utilize, the sample may be classified as non-cohesive or having plastic characteristics based upon procedures outlined in Practice or other means of determining the soil properties.
Note 1: The quality of the result produced by this standard 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 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice does not in itself ensure reliable results. Reliable results depend on many factors; Practice provides a means of evaluating some of those factors.
Note 2: As outlined in , if the sample is dry sieved after washing, such as for Test Methods or , some material may pass the 75-μm (No. 200) sieve that did not pass during washing operations. The material passing the 75-μm (No. 200) sieve may be a significant amount for samples with a high percentage of silt or clay.
1.1 These test methods cover the determination of the amount of material finer than a 75-μm (No. 200) sieve by washing of material with a maximum particle size of 75 mm (3 in.).
1.2 The methods used in this standard rely on the use of water or a dispersant to separate and remove materials finer than a 75-μm (No. 200) sieve. During these processes soluble substances, such as salts and other minerals, may also be removed. It is not within the scope of this standard to differentiate between the removal of fine particles and soluble substances. It is recommended that materials containing significant amounts of soluble substances be tested using other methods of separation.
1.3 Two methods for determining the amount of material finer than the 75-μm (No. 200) sieve are provided. The method to be used shall be specified by the requesting authority. If no method is specified, the choice should be based upon the guidance given in , , and .
1.3.1 Method A—Test specimen is dispersed by soaking in water prior to wash sieving.
1.3.2 Method B—Test specimen is dispersed by soaking in a dispersing solution prior to wash sieving.
1.4 Units—The values stated in SI units are to be regarded as standard. Except the sieve designations are typically identified using the “alternative” system in accordance with Specification , such as 3 inch and No. 200, instead of the “standard” of 75-mm and 75-μm, respectively. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method. The use of balances or scales recording pounds of mass (lbm) shall not be regarded as nonconformance with this standard.
1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice , unless superseded by this test method.
1.5.1 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.
1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.