Consistency and Plasticity
Cohesive soils change their state depending on the water content. When the water content is very high, these soils become liquid. When the water content decreases, they transition from a liquid to a plastic condition, then to semi-solid and finally to a solid condition.
Thus, with a decreasing water content, cohesive types of soil become less mouldable, while their strength increases.
The water contents at which the soil consistency is transformed from one into another condition are called condition- or consistency limits according to Atterberg [Atter11].
Two of these limits are used for a classification of fine types of soil [DIN18122]:
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Liquid limit wL: Water content of the soil at the transition from the plastic to the liquid condition [ASTM D423]
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Plastic limit wP: Water content of the soil at the transition from the stiff to the plastic condition [ASTM D424]
