Liquid limit and plastic limit of soil

Soil is an essential ingredient in agriculture and building construction. Soil has to be tested properly before using it. Liquid limit and plastic limit are two important parameters of soil. Liquid limit which is expressed in % is the water content at which the soil transforms from zero strength state to infinitesimal strength state. It is very difficult to determine accurately the actual liquid limit value. Plastic limit which is also expressed in % is the moisture content at which the soil has the smallest plasticity. Beyond plastic limit, soil behaves like a semi solid. The difference in moisture content between the liquid and plastic limit is termed as the plasticity index. Plasticity chart is a chart between liquid limit and plasticity index of soil materials. Liquid limit and plastic limit values are used for the classification of fine-grained soils. For the determination of plastic limit and liquid limit, we require a casagrande liquid limit device, a glass plate, a rod, a grooving tool, a spatula, some water containers, a wash bottle, a mixing bowl, a sensitive balance and a drying oven.