![](https://i0.wp.com/csisoiltesting.com/wp-content/uploads/2019/01/Plasticity-Index-Testing.png?resize=640%2C480)
The plasticity index (PI) is a measure of the plasticity of a soil ie. The range of moisture content in which the soil remains plastic in nature, between a solid and a liquid. Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 tend to have little or no silt or clay.