Performed on materials passing the number 40 sieve, which test helps determine whether a soil is clayey (C) or silty (M)?

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Multiple Choice

Performed on materials passing the number 40 sieve, which test helps determine whether a soil is clayey (C) or silty (M)?

The test hinges on plasticity and cohesiveness of fine soils. When you work a small amount of material that passes a 40 sieve with water until it’s plastic, you roll it between your fingers to form a ribbon. Clay-rich soils have strong cohesive forces from clay minerals, so they can be rolled into a long, continuous ribbon. Silty soils lack that cohesion and form only a short ribbon or crumble. Because this moist ribbon behavior directly shows how strongly the particles stick together, it’s the best quick indicator for telling a clayey soil from a silty one in the fine fraction. The other options don’t measure this cohesive, plastic behavior—their results aren’t reliable for distinguishing clay from silt.

The test hinges on plasticity and cohesiveness of fine soils. When you work a small amount of material that passes a 40 sieve with water until it’s plastic, you roll it between your fingers to form a ribbon. Clay-rich soils have strong cohesive forces from clay minerals, so they can be rolled into a long, continuous ribbon. Silty soils lack that cohesion and form only a short ribbon or crumble. Because this moist ribbon behavior directly shows how strongly the particles stick together, it’s the best quick indicator for telling a clayey soil from a silty one in the fine fraction. The other options don’t measure this cohesive, plastic behavior—their results aren’t reliable for distinguishing clay from silt.

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