Numerical modelling of degradation of cement paste under external sulfate attack

In this study, a numerical method is developed to simulate the degradation of cement paste when subjected to sodium sulfate solutions. The proposed numerical method accounts for ionic diffusion, chemical reactions and the damage propagations, which are three main phenomena accompanied with degradation. A modified Poisson-Nernst-Planck model is developed to model the diffusion of multiple ions in a gradually degraded material. The cracking suction effect is introduced to consider the suction action caused by the newly-formed unsaturated cracks, which would accelerate the diffusion process within the cracking area. The proposed model is applied to model the experiments reported in the literature. The numerical results obtained agree very well with those from experiments.