A nest of two sieves consisting of an upper sieve with openings in the range of 2.36 mm ( # 8 ) and 1.18 mm ( # 16 ) , and a 75 - μm ( # 200 ) lower sieve are used when washing.

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When washing aggregates for gradation testing, you need a sieve stack that keeps size ranges separated while the wash removes fines. The described nest does just that: two coarse sieves on top with openings of about 2.36 mm and 1.18 mm, and a very fine bottom sieve of 75 μm. This setup provides a staged separation so that the largest pieces stay on the upper sieves, the next size range is held by the next sieve, and the finest material is captured by the 75 μm sieve. This arrangement helps prevent fines from being lost in the wash water and allows accurate weighing of each size fraction after drying. Using only a single sieve or not specifying would not give you the needed separation during washing, so this configuration is the correct one.