Material finer than the 75-µ (No. 200) sieve can be separated from larger particles much more efficiently and completely by wet sieving than through the use of dry sieving. Therefore, when accurate determinations of material finer than 75 µm in fine or coarse aggregate are desired, this test method is used on the sample prior to dry sieving in accordance with Test Method CNS 486. The results of this test method are included in the calculation in Test Method CNS 486, and the total amount of material finer than 75 µm by washing, plus that obtained by dry sieving the same sample, is reported with the results of Test Method CNS 486.
MTI laboratories are accredited by TAF (ISO/IEC 17025) to perform testing standard CNS 491 for Materials Finer than 75-µm (No. 200) Sieve in Mineral Aggregates by Washing.