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.

This study investigated the effects of light-burned magnesia, fly ash (FA), dolomite powder (DP), and limestone powder (LP) contents on the performance of magnesium oxychloride cement lean concrete (MOCLC). The effects of light-burned magnesia and mineral admixture content on the mechanical properties and durability of MOCLC were tested by the compressive strength test, splitting strength test, water resistance test, shrinkage test, and fatigue test, respectively. The results revealed that the optimum dosage of MgO was 4%. The optimum dosages of FA, DP, and LP were 25%, 20%, and 20% of the cement dosage, respectively. The compressive and splitting strengths of the MOCLC were decreased by the addition of FA and DP. Due to part of the internal pores of MOCLC were filled with FA and DP, the decomposition of the main strength phase 5Mg (OH)2·MgCl2·8H2O (phase 5) was suppressed and the water resistance of MOCLC was improved. The addition of FA and DP also improved the shrinkage resistance, and the fatigue resistance of MOCLC was also improved by the addition of FA and DP. The water resistance, shrinkage, and fatigue properties of MOCLC with a FA content of 25% were better than those of MOCLC with DP and LP.