What is Atterberg Limits tests?

The Atterberg Limits tests are designed to determine the plasticity of finer grained soils. These tests are performed on the fraction less than 0.425 mm (passing the No. 40 Sieve). 

• The liquid limit (LL) is the moisture content at which the soil sample passes from the plastic state to the liquid state.
• The plastic limit (PL) is the moisture content at which the soil sample passes from the semisolid to the plastic state.
• The plasticity index (PI) is the difference in moisture content from the threshold of the plastic to liquid state to the threshold of the semisolid to plastic state.