Studies of the effect of recycled aggregates on flexural, shear, and bond splitting beam structural behavior

This paper reports on a research program designed to investigate the structural behavior of reinforced concrete beams prepared by replacing different percentages of natural coarse aggregates (NCA) with recycled coarse aggregates (RCA), sourced from tested concrete cylinders in Ready/Mix plants. One objective was to recycle and reuse the crushed concrete cylinders in the construction industry and mitigate its negative environmental impact. The variables were the percentage replacement of NCA with RCA [0(control), 40, or 100%] and the mode of failure of the tested beams (flexure, shear, or bond splitting of the concrete cover in the splice region). The significance of the study stems from the source of the recycled aggregates, the fact that the reported research covers the three structural modes in one program, and that all reported bond tests in the literature investigated the pullout strength of bars anchored in RCA specimens or bond strength of reinforcement in beam-end specimens rather than the actual bond splitting behavior of bars spliced in RCA structural beams. Experimental results showed minimum difference in the peak load and load-deflection histories attributed to the percentage replacement of NCA with RCA. Results were compared with theoretical values computed using the ACI Building Code and with results of few previous research programs. Moreover, nonlinear finite element models were built to validate the experimental test results. The experimental and numerical results were comparable.