Experimental study on the influence of recycled aggregate substitution rate on the mechanical properties of recycled aggregate concrete under sulfate erosion conditions

To investigate the degradation of recycled aggregate concrete (RAC) under sulfate attack, four groups of RAC cubic specimens (168 in total) were prepared. The influence of recycled coarse aggregate (RA) replacement ratio on the mechanical properties of RAC under sulfate exposure was analyzed. Strength degradation at different exposure durations was assessed, and microstructural changes were examined using scanning electron microscopy (SEM). The results show that: (1) both compressive and splitting tensile strengths decrease with increasing RA replacement ratio, with the reduction in splitting tensile strength being more pronounced; (2) the compressive strength initially increases slightly under sulfate exposure, then gradually declines, with higher RA replacement ratios accelerating the degradation; (3) the decrease in splitting tensile strength is slightly greater than that of compressive strength over time; and (4) this decline in splitting tensile strength becomes more significant as the RA replacement ratio increases. Based on the experimental data, predictive models were established for the degradation of compressive and splitting tensile strengths at various sulfate exposure ages, incorporating the effect of RA replacement. These models effectively characterize the strength deterioration behavior of RAC under prolonged sulfate immersion.