Based on Fick’s second law and the damage evolution due to sulfate attack, a new model is proposed to analyze the diffusion of sulfate ions in concrete. The relation between erosion damage and erosion time, as well as the concentration of sulfate ions is firstly investigated by virtue of the ultrasonic experimental results. Furthermore, the damage evolution is treated as the increase of porosity, and a new nonlinear differential equation on the diffusion of sulfate ions is established by substituting such an increasing porosity into Fick’s law. The nonlinear diffusion equation is then solved by numerical method. It is found that the erosion damage can significantly affect the diffusion of sulfate ions in concrete.

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The debonding of a rigid particle embedded in an infinite non-linear viscoelastic material is investigated in this paper. Under sphere-symmetric deformation, a non-linear equilibrium equation expressed by velocity of a particle in the viscoelastic matrix material is derived. The strain rate is obtained by solving non-linear equation in terms of iterative method. According to the energy criterion, the critical instant of the interfacial debongding is calculated. Numerical results show that the influence of non-linear viscosity on the interfacial debonding is significant.

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