Poroelastic model for concrete exposed to freezing temperatures

Abstract

There are many competing theories to model concrete exposed to freezing temperatures but few of them provide comprehensive quantitative predictions of the mechanical behavior, while accounting for the multi-scale physics of the confined crystallization of ice. When a part of the liquid in the pores solidifies, a pressure build up is generated, and excess liquid is expelled from the freezing sites towards the remaining part of the porous network. In turn, with increasing cooling a cryo-suction process drives the liquid towards the frozen sites. Unsaturated poroelasticity theory provides new perspectives on the computation of stresses and strains developed in such a complex mechanism. The formulation includes the deformation of all the phases during the freezing process. Special attention is given to the influence of entrained air-voids on the frost resistance of the porous material. The analysis indicates that the air voids act both as expansion reservoirs and efficient cryo-pumps whose respective effects are quantitatively assessed. The theory also allows for the estimation of the critical spacing factor. Numerical simulations are conducted to study the effect of pore size distribution on the critical spacing factor and on the internal pressurization within the porous material as it freezes.