What does the plasticity index indicate about soil properties?

The plasticity index is a key indicator of the moisture range within which a soil exhibits plastic behavior. It is specifically calculated as the difference between the liquid limit and the plastic limit of the soil. Essentially, the plasticity index provides vital information about how a soil will behave when subjected to moisture changes. A higher plasticity index suggests that the soil can undergo significant deformation without cracking, indicating a greater capacity for workability when wet. This characteristic is essential in determining the suitability of the soil for construction and engineering projects, as it influences factors such as compaction, stability, and moisture retention.

The other choices relate to different aspects of soil properties but do not directly correlate with the concept of plasticity. The density of soil particles, color variations, and chemical composition all provide distinct information about soil that does not pertain to its plasticity behavior or its moisture-related characteristics. Thus, understanding the plasticity index is crucial for soil classification and evaluating how soil properties change with water content.