Flexural behavior of recycled aggregate concrete beams strengthened with carbon fiber reinforced polymer

Using recycled aggregate in the construction of reinforced concrete (RC) buildings has become essential to reduce the waste produced from demolished buildings. In this paper, the influence of using carbon fiber reinforced polymer (CFRP) in strengthening of RC beams with recycled coarse aggregate (RCA), as a partial/full replacement for natural coarse aggregate (NCA), was experimentally investigated. Twelve RC beams with various RCA ratios (0%, 30%, 70%, and 100%) were prepared and tested under four-point loading. Four beams without CFRP were tested till failure while the other eight beams were subjected to service loads then strengthened using CFRP and re-tested till failure. The cracking pattern, deflection, as well as strain in longitudinal and transversal reinforcement were recorded. The failure loads of the tested beams were compared to those predicted from various international design codes. Results showed that the flexural cracks appeared in specimens with 100% RCA earlier than those with NCA. Moreover, the increase in RCA% resulted in resisting tensile stresses by stirrups at a lower load value and achieving a more ductile behavior. Also, the experimental results showed that including RCA in beams slightly decreased the failure load for both strengthened and un-strengthened RC beams. Furthermore, beams with higher amount of RCA experienced more deflections than those with lower amount of RCA. Such behavior was found more prominent in the CFRP strengthened beams.