Expansive clay

Expansive clay is a type of clay that is known as a lightweight aggregate with a rounded structure, with a porous inner, and a resistant and hard outer layer.

It is a clay or soil that is prone to large volume changes (swelling and shrinking) that are directly related to changes in water content. Soils with a high content of expansive minerals can form deep cracks in drier seasons or years; such soils are called vertisols. Soils with smectite clay minerals, including montmorillonite and bentonite, have the most dramatic shrink-swell capacity.