Performance of reinforced recycled aggregate concrete beams in flexure: experimental and critical comparative analysis

The necessity of sustainable approaches in the construction sector persuades the researchers to utilize the recycled coarse aggregate (RCA) extracted from waste concrete and study the performance of structural members by substituting natural coarse aggregate (NCA) with the RCA. In the present context, the flexural performance of RAC beam was examined on fourteen numbers of beams by completely replacing the NCA with RCA and using four different longitudinal reinforcement ratios (rho) of 1.61, 1.31, 0.75 and 0.42%. In order to improve the quality of RAC, the particle packing method (PPM) of mix design approach was employed along with the two stage mixing approach (TSMA). The improved mechanical properties owing to the combined effect of PPM design mix and TSMA are also translated in the flexural performance of RAC beams even at 100% use of RCA. A maximum reduction of 35, 4 and 5% in cracking load, yield load and ultimate load, respectively, are observed in RAC beams as compared to the conventional concrete beams. However, the undesirable shear tension mode of failure was witnessed for RAC beams at rho = 1.61%. A database is prepared by compiling the reported experimental results of RAC beams with shear reinforcement in the available literature. The suitability of the existing expressions to predict the ultimate load is verified for RAC beams and it is observed that, the number of unconservative predictions is significant. In this scenario, an equation is proposed to predict the ultimate load of transversely reinforced RAC beams by operating the flexure database, which shows good correlation with the available experimental results. Further, the increment in shear strength of RAC beams due to the inclusion of stirrups is estimated by using the derived expression.