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 C136. The results of this test method are included in the calculation in Test Method C136, 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 C136. Usually, the additional amount of material finer than 75 µm obtained in the dry sieving process is a small amount. If it is large, the efficiency of the washing operation should be checked. It could also be an indication of degradation of the aggregate. Plain water is adequate to separate the material finer than 75 µm from the coarser material with most aggregates. In some cases, the finer material is adhering to the larger particles, such as some clay coatings and coatings on aggregates that have been extracted from bituminous mixtures. In these cases, the fine material will be separated more readily with a wetting agent in the water.
KeywordsGrading - Particle Size - Washing
ICS CODE91.100.15 (Mineral materials and products)
ASTM C117-17, Standard Test Method for Materials Finer than 75-µm (No. 200) Sieve in Mineral Aggregates by Washing, ASTM International, West Conshohocken, PA, 2017, www.astm.org