Modeling the transport of ions in unsaturated cement-based materials

This paper gives the details of the multiionic transport model STADIUM^® intended to describe the degradation of cement-based materials exposed to aggressive environments. The main algorithm is based on an operator splitting approach. The first part of the calculations is dedicated to solving the transport equations without considering the chemical reactions. The concentration profile of each ionic species is calculated by taking into account diffusion, electrical coupling between the ions, chemical activity effects and advection caused by a capillary suction flow. In the second part, a chemical module corrects the concentration profiles to enforce the equilibrium between the pore solution and the various solid phases of an hydrated cement paste. The model is compared to experimental results of hydrated cement pastes exposed to pure water and sodium sulfate solutions. Long term simulations were also performed to analyze the behavior of the algorithm.