Long-term performance of recycled aggregate concrete beams exposed to 10 years of loading and chloride environments

Abstract

To address concerns over the long-term durability of reinforced concrete beams incorporating recycled coarse aggregate (RCA), this study investigates beams with RCA replacement rates of 0 %, 50 %, and 100 % under ten years of sustained loading and chloride exposure. A comprehensive evaluation was conducted to examine the effects of RCA replacement on cracking patterns, carbonation depth, chloride ingress, reinforcement corrosion, and residual flexural capacity. The results show that higher RCA replacement rates significantly increase both transverse and longitudinal cracking on the beam surfaces, caused by the combined effects of localized stresses from sustained loading and chloride-induced reinforcement corrosion. As RCA replacement increases, both carbonation depth and chloride concentration rise, with notable differences between tension and compression zones. These interactions between RCA material properties and environmental exposure accelerate corrosion in both longitudinal and stirrup reinforcement, particularly in tensile regions. Although RCA replacement rates did not notably alter the failure modes, at damage ages of 120 months, higher RCA replacement correlated with increased deflection and a significant reduction in residual flexural capacity, with a 1.27 % reduction for RAC50 and a 12.94 % reduction for RAC100 at 120 months. To better predict the flexural strength of corroded concrete beams, this study introduces a time-dependent flexural capacity reduction coefficient (β_r), incorporating RCA replacement rate (r) and loading time (t). This research underscores the critical need to consider RCA replacement rates and long-term environmental exposure when designing concrete beams to optimize durability in aggressive environments.