Seismic performance of full-scale RC columns containing high proportion recycled aggregate

The potential for utilizing high proportion recycled aggregates sourced from low strength waste concrete in new concrete construction is investigated in this paper. A comprehensive experimental program, consisting of ten full-scale, flexure critical reinforced concrete columns, five of which were constructed of natural concrete aggregate and five of which contained approximately 50% recycled concrete aggregate replacing the mid-sized coarse natural aggregate, was conducted to determine the effects of different axial loads and different spacings of transverse reinforcement on the seismic characteristics of columns incorporating recycled concrete aggregates. Seismic characteristics were quantified by analysis of hysteretic response, energy dissipation capacities, damage progression, residual displacement, and strain distribution of the longitudinal reinforcement. The test results indicate that the reinforced concrete columns constructed of natural aggregate concrete and those constructed of recycled aggregate concrete exhibit similar seismic performance, despite the fact that the compressive strength of the recycled aggregate concrete was slightly lower than that of the natural aggregate concrete. A theoretical study was then conducted to predict the load–displacement response of the columns. The comparison of the experimental data with the results of these theoretical calculations indicated that conventional RC design theory applied to columns incorporating natural aggregate is also valid for columns incorporating recycled aggregate. Finally, the confinement effect of the transverse reinforcement in columns subjected to low axial load were also critically evaluated for columns built with recycled aggregate concrete.