Stress-strain behaviour of steel confied recycled aggregate concrete

Currently, utilization of recycled concrete aggregates is limited to non-structural applications owing to inferior properties. On the other hand, effect of confiement due to transverse reinforcement is ignored in the current design practice of concrete compression members. The focus of this study is to improve the performance of recycled aggregate concrete through confiement by pre-existing transverse reinforcement i.e., steel spirals in compression members leading towards sustainable construction. For this purpose, concrete cylinders were cast with 0%, 50% and 100% replacement ratios of recycled concrete aggregates and confied by steel spirals having pitches of 20 mm, 30 mm and 40 mm. Axial stress-strain behaviour of steel confied recycled aggregate concrete was examined in this study. Results showed that improved ductility and post peak behaviour were observed with the increase in confiement pressure. Increase in peak stress, peak strain and ultimate strain of concrete specimens was also observed with the increase in confiement pressure. Concrete specimens having 50% and 100% replacement ratio of recycled concrete aggregates and confied with 20 mm pitch of spiral reinforcement showed peak stresses higher than unconfied control specimens. Moreover, all the confied recycled aggregate concrete specimens showed peak strain, ultimate strain and toughness higher than unconfied control specimens. Currently, no such work is available in the extant literature to predict the axial stress-strain behaviour of steel confied recycled aggregate concrete. Based on the experimental results, a stress-strain model is proposed in this study. For this purpose, the effect of replacement ratios of recycled concrete aggregates is incorporated by modifying the parameters of stress strain model for spirally confied normal aggregate concrete. The proposed model can effectively predict the stress-strain behaviour of both steel confied normal and recycled aggregate concrete.