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 Note 2).
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 D2488 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 D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.
Note 2: As outlined in 5.1, if the sample is dry sieved after washing, such as for Test Methods D422 or D6913, 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......
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