Which symbol indicates low plasticity clay?

The symbol that indicates low plasticity clay is 'CL'. This designation is part of a system used in soil classification, particularly in the Unified Soil Classification System (USCS). In this system, 'C' denotes clay, while the letters following it specify the characteristics of that clay.

The distinction of 'L' in 'CL' stands for low plasticity, indicating that this type of clay has a plasticity index of less than 7. Low plasticity clays exhibit a relatively small change in consistency when subjected to changes in moisture content, meaning they are less likely to deform when wet, which is important information in engineering and construction contexts. This is critical in geotechnical assessments, where understanding soil behavior is essential for the stability of structures.

In contrast, the other symbols refer to different types of clays and their plasticity characteristics. 'CH' indicates high plasticity clay, 'ML' denotes low plasticity silt, and 'MH' refers to high plasticity silt. Each of these distinctions plays a significant role in understanding the engineering properties of soils, but for low plasticity clay specifically, 'CL' is the correct designation.