Drying of concrete: modelling of a hydric damage

Abstract

Drying shrinkage of concrete induces the formation of microcracks that damage concrete structures. This damage can be characterised by deteriorating material elastic properties over the years. In this investigation, we present a modelling of this phenomenon, simple and easy to be implemented, and that should allow engineers to predict cracking as a durability indicator and to model ageing. We first present the basic hypotheses of our model, and formulate hydric damage by using an isotropic scalar variable proportional to the decrease in water content. Uncoupling between drying-induced damage and classical mechanical damage is assumed. Two simple applications are proposed. For the one-dimensional drying case (cylindrical specimens), we compare the simulation of the variation in time of the dimensionless stiffness with experimental results in uniaxial compression. A good adequacy is observed. For the bi-dimensional drying case (prismatic specimens), the knowledge of measurements of mass loss and average longitudinal shrinkage in time allows us to predict the value of drying induced stresses in a cross section, taking hydric damage into account. A better estimate of stresses induced by drying is proposed.