Numerical Simulation of Concrete Attacked by Sulfate under Drying–Wetting Cycles Coupled with Alternating Loads

Concrete structures such as rigid pavements, tunnels, and runways at airports are usually subject to fatigue traffic loading during their service life. Research on the aftereffects of drying–wetting cycles coupled with alternating loads on concrete erosion in saline–alkali and coastal areas is of considerable practical importance. For this study, we utilized specimens of dimensions 100 mm × 100 mm × 400 mm with strength ratios of C30, C40, and C50. We incubated the concrete samples in a 24 h/24 h drying–wetting cycle with sodium sulfate solutions of different concentrations as we applied alternating loads. We conducted ultrasonic wave velocity tests every 30 days from the 60th day of the experiment to determine the change in the sound velocity of the concrete over the course of 360 days. In addition, we examined the invasion depth of SO42− with time. Based on the change in sound velocity, we developed the damage degree function, and we modified the diffusion coefficient of SO42− in concrete in accordance with the coupling of drying–wetting cycles and alternating loads. We conducted a simulation on SO42− penetration depth, and the results were in reasonable agreement with those obtained by experimental testing.