The liquid limit (LL) and plastic limit (PL) are commonly used and are dependent on soil parameters such as particle size and specific surface area of the particles able to attract water molecules. Depending on the moisture content, the soil may be in any of the four states:

The boundary at which the change in behavior takes place is defined based on the behavior of the soil sample. Karl Terzhagi and Arthur Casagrande later refined and standardized the tests which are now widely used to determine the LL, PL, and SL of soils.Ĭlay soil changes consistency and behavior depending on its moisture content. The Atterberg limits test is named after the Swedish chemist Albert Atterberg who was the first to develop a classification system to determine the different states and limits of soil consistency. It can be used to distinguish between silt and clay in its different types and determines the shrinkage limit (SL), plastic limit (PL), and liquid limit (LL) of the soil sample. The test aids in the classification of soil and its plasticity characteristics and evaluates the shrink/swell potential of near-surface soil.

The test for Atterberg limits is performed on the fraction of soil that will pass through a No. V) Repeat the process at least twice more with fresh samples of plastic soil each time.The Atterberg limits test is a classification test used to determine the moisture content at which fine-grained clay and silt soils transition between the different phases. Iv) Collect and keep the pieces of crumbled soil thread in the container used to determine the moisture content. Iii) Repeat the process of alternate rolling and kneading until the thread crumbles.

Knead the soil to reduce the water content and roll it into a thread again. of the threads can be reduced to less than 3mm, without any cracks appearing, it means that the water content is more than its plastic limit. The rate of rolling should be between 80 to 90 strokes per minute to form a 3mm dia. I) Take about 8g of the soil and roll it with fingers on a glass plate. Procedure to determine The Plastic Limit Of Soil Mix the soil with distilled water in an evaporating dish and leave the soil mass for naturing. Take out 30g of air-dried soil from a thoroughly mixed sample of the soil passing through 425µm IS Sieve. Iii) Container to determine moisture content I) Porcelain evaporating dish about 120mm dia. It begins to crumble when rolled into threads of 3mm dia.

This test is done to determine the plastic limit of soil as per IS: 2720 (Part 5) – 1985.The plastic limit of fine-grained soil is the water content of the soil below which it ceases to be plastic.

Plastic limit test