A constitutive model for drying of a partially saturated porous material

A new constitutive model for drying of an elastic porous material is presented. The model is derived by decomposing the boundary value problem of drying into parts for which an explicit solution is readily available. The mathematical form differs from models developed using either the concept of equivalent pore pressure or average pore pressure. Instead of pressure averaging, the extent of weakening of the solid due to void inclusions, a material parameter, is found to be critical for the proper predictions of the volumetric strains. The model is applicable to drying under conditions where multi-layer adsorption of liquid persists, i.e. where the effects of solid surface energy are negligible, and where capillary pressure is the primary loading stimulus. A particular (and simple) form of the model is compared with experimental data for partially dried cement paste and Vycor (TM), glass, and is shown to provide a much better agreement than previous models based on average pore pressure. Implications to the poromechanics and the effective stress of partially saturated porous media are discussed. (C) 2008 Elsevier Ltd. All rights reserved.