Modeling Drying Shrinkage and the Creep of Concrete at the Meso-Level

Abstract

Creep and shrinkage are complicated time-dependent processes taking place in cementitious materials. Creep refers to a stress-induced increasing deformation at constant stress while shrinkage is stress-independent. In typical concretes, the most significant part of shrinkage is represented by drying shrinkage; it is caused by a decrease in relative humidity of pores which leads to an increase in capillary tension of pore water and in the solid surface tension at pore walls. Experimental data indicate that the ultimate value of drying shrinkage-measured on concrete and mortar specimens is a nonlinear function of the ambient relative humidity. The nonlinear behavior is partially caused by microcracking, and partially by creep of the cement matrix. On the other hand, drying shrinkage of hardened cement paste, measured on very thin specimens at gradually decreasing relative humidity, is found to be a linear function of relative humidity. The aim of this paper is to assess the nature of the macroscopic shrinkage computed employing finite element simulations at the meso-scale level in which the drying cement paste is described by a viscoelastic model based on the Microprestress- Solidification Theory (MPS) with tensile cracking and with a constant shrinkage coefficient.