A quantitative assessment of the parameters involved in the freeze–thaw damage of cement-based materials through numerical modelling

Abstract

Abstract Degradation of concrete due to freeze–thaw cycles is a subject that is still debated. For many years, some predictive models have been developed by taking into account the physics, but the choice of parameters which drive the frost kinetics and the couplings are often arbitrarily chosen to fit experimental measurements. Moreover, recalibration becomes necessary each time the mix design or the environmental conditions vary. This article presents a quantitative assessment of the effect of the mechanisms induced by the freeze–thaw action on the internal damage of cementitious materials, using a descriptive numerical methodology at the microscale. The proposed thermo-mechanical model is based on thermodynamic considerations and physical processes related to freeze–thaw applied to virtual microstructures of cement pastes. A statistical study on the main parameters, which govern the frost action, has been performed to highlight their significance on the thermal strain. The numerical results show that the presence of supercooling and delayed nucleation of ice is by far the most harmful cause of degradation. Both the water-to-cement ratio and the minimum freezing temperature reached during freeze–thaw cycles contribute considerably to the deterioration of the material and a decrease in the Young s modulus. It is shown that the effect of de-icing salt ions present in the pore solution depends on the degree of saturation, and that the critical degree of saturation depends on the minimum temperature. The study also demonstrates the beneficial role of using entrained air to reduce damage caused to cement paste.