Dynamic mechanical response and damage analysis of steel fiber-reinforced recycled aggregate concrete under repeated impact loading

• The test of multiple impacts of SFRRAC was carried out. • The effect of impact times on mechanical response was analyzed. • The impact damage under different changing parameters was discussed. Steel fiber-reinforced recycled aggregate concrete (SFRRAC) offers a sustainable approach to construction waste recycling; however, its dynamic mechanical response and damage evolution under repeated impact loading remain unclear. Thus, this study by varying the parameters of impact time, recycled coarse aggregate replacement ratios (0%, 50%, and 100%), and steel fiber volume fractions (0.5%, 1.0%, 1.5%, and 2.0%), 12 groups of cylindrical specimens were engineered for split Hopkinson pressure bar impact tests. The failure modes of SFRRAC specimens subjected to multiple impact loads were examined. The dynamic stress–strain relationships of SFRRAC were measured at various impact pressures. The effects of impact times and substitution ratios on response indicators and the damage factor were analyzed. The results showed that increasing impact times led to continuous decreases in peak stress, progressive increases in peak strain, more severe specimen failure (cracked but not scattered), and rapid reductions in impact toughness—particularly a 16.12%–33.34% drop from the third to fourth impact. Higher substitution ratios monotonically lowered mechanical response and raised the damage factor, with a 50% increase in substitution causing 10.1%–14% less toughness and 22%–35% more damage. A 2.0% steel fiber content provided the highest peak stress across all RCA ratios and the slowest damage buildup under repeated impacts. The findings of this study provide fundamental support for the engineering application of SFRRAC under dynamic loads.