Which property is evaluated in assessing the plasticity of soil?

Plasticity in soil refers to the ability of soil to deform and retain its shape without cracking or breaking when subjected to stress. This property is primarily determined by the moisture content, specifically the moisture content at which the soil exhibits maximum deformation before changing its consistency.

When evaluating soil plasticity, a critical factor is the plasticity index, which indicates the range of moisture content over which the soil behaves plastically. The moisture content at maximum deformation essentially identifies the point where the soil transitions from a plastic to a brittle state, giving insight into its workability and stability in engineering and construction applications.

The other properties mentioned, like the weight of the soil, particle size distribution, and color, do influence soil characteristics but are not direct measures of plasticity. Weight and color provide information about soil composition and conditions but do not relate directly to how the soil will behave under mechanical influences. Particle size distribution can affect the general properties of the soil, but does not by itself indicate how well it will deform under moisture conditions. Thus, moisture content at maximum deformation is the key factor in assessing soil plasticity accurately.