Shear and flexural performance of reinforced concrete beams with recycled concrete aggregates

Abstract This study investigates the effects of recycled concrete aggregate (RCA) content and stirrup spacing on the structural performance of reinforced concrete beams (RCBs) under flexural and shear loading. A total of 24 RCB specimens were cast with RCA replacement ratios of 0, 10, 20, and 40%, and tested under four different stirrup spacings: 100, 160, 200, and 270 mm. The experimental program evaluated key structural parameters, including load-bearing capacity, stiffness, ductility, and energy dissipation. The results demonstrated that increasing the RCA content generally led to reductions in both flexural and shear strength. The most significant shear strength loss (46.86%) occurred at 40% RCA with 270 mm stirrup spacing, while the highest flexural load reduction (11.24%) was observed in beams with Ø10 longitudinal reinforcement and 40% RCA. Moreover, although higher RCA content generally reduced stiffness, ductility, and energy dissipation, specimens with wider stirrup spacing exhibited relatively better performance under shear, suggesting that transverse reinforcement can partially mitigate RCA-induced performance losses in shear-dominated beams. These findings suggest that while RCA can be used in RCBs, proper detailing of transverse and longitudinal reinforcement is essential to maintain adequate structural performance.