Experimental study on the flexural behavior of reinforced concrete beams with RCA under biaxial loading

Abstract

This study investigates the flexural behavior of reinforced concrete beams containing recycled concrete aggregate (RCA) under inclined loading conditions. Four concrete mixtures with RCA replacement ratios of 0%, 30%, 50%, and 75% were developed and tested. Beams with square (250 × 250 mm) and rectangular (150 × 350 mm) cross-sections were subjected to inclined loading at angles of 0°, 45°, and 68°. The experimental results included first cracking load, ultimate load, mid-span deflection, failure mode, crack pattern development, steel strain response, ductility index, and energy absorption capacity. The results showed that increasing RCA content generally reduced cracking and ultimate loads due to weaker interfacial transition zones (ITZ) and lower stiffness. For square beams, higher load inclination angles improved load-carrying capacity and energy dissipation. In rectangular beams, inclined loading transferred part of the load toward the direction of lower flexural stiffness, resulting in reductions in both cracking and ultimate loads. Failure mode observations indicated predominantly flexural behavior for all specimens, although crack inclination and compression damage increased with loading angle. Moderate RCA replacement (30%) slightly improved ductility and energy absorption, whereas higher replacements (50%–75%) significantly decreased these parameters. Overall, the performance of reinforced concrete beams was influenced by RCA content, cross-sectional geometry, and load inclination under inclined loading conditions.