PLASTICITY OF CLAY
The plasticity of clay can be defined as its ability to form a plastic mass with water. The mass can be easily modulded to any shape.
Dry clay is not a plastic , and a certain amount of water has necessarily to be added to produced the required plasticity.
The amount of water required to make a clay plastic, depends on the size and shape of the clay particles, their surface characteristics, and presence of electrolytes (salt).
For every clay, there is a certain minimum water content, bellow which it ceases to behave as plastic material and becomes crumbly. This is called the plastic-limit of a clay.
As the proportion of water increases, the clay becomes more and more plastic, until the point is reached at which it starts flowing and becomes wet and sticky. This point is called liquid-limit. The difference in the water content between the liquid limit and the plastic –limit, is called the plasticity index, which represents the plasticity-range of the clay.
