Expansion of consolidated material after release of load.

An understanding of the expansion phenomena of compressed materials is essential to improving the technique of forming by expression in ceramics industries and other processes. In this study, a slurry of Korean kaolin–Solka floc mixture was used as experimental material. The slurry was consolidated in a compression cell at constant pressure, resulting in a semisolid material with uniform void ratio. The expansion process of such a homogeneous material was investigated experimentally and theoretically under the condition in which the compression pressure was released momentarily and the material was saturated with liquid during expansion. Expansion of a homogeneous material is very similar to consolidation of a semisolid material, and can be analyzed well by use of the Terzaghi–Voigt combined model, although the expansion proceeds considerably more slowly than does consolidation under the same change of compression pressure. It is found that the ratio of secondary deformation to total deformation in expansion is much larger than that in consolidation.