Measuring the plasticity of clays: A review

Plasticity is the outstanding property of clay–water systems. It is the property a substance has when deformed continuously under a finite force. When the force is removed or reduced, the shape is maintained. Mineralogical composition, particle size distribution, organic substances and additives can affect the plasticity of clays. Several measuring techniques and devices were proposed to determine the optimal water content in a clay body required to allow this body to be plastically deformed by shaping. In this review, methods of evaluating the plasticity of clay–water systems are presented. Despite the advance in the theory of the plasticity and the methods of measurement, a common procedure for all types of materials does not exist. The most important methods are those that simulate the conditions of real processing. ► Plasticity is related to deforming a substance continuously under a finite force. ► Composition, particle size, organic matter and additives may affect clay plasticity. ► Several techniques are used to determine the optimal water content of clays. ► Methods for evaluating the plasticity of water-clay systems were reviewed. ► A consolidated method for measuring clay plasticity still does not exist.