Experimental study on the shear strength of recycled aggregate concrete beams

In concrete beam design, the shear capacity of the concrete beam is of great interest because shear failure is associated with an abrupt failure mode that undermines the flexural performance of the beam. Recently, because of the increasing cost of natural resources and environmental concerns, the use of recycled aggregate (RA) in construction is becoming the standard practice. However, the effects of recycled aggregates on the shear strength of concrete have not been fully examined. In this study the effects of RA on concrete shear strength are studied experimentally by performing flexural tests on 20 RA concrete beams with various combinations of span-to-depth ratios (a/d 1.50, 2.50, 3.25), longitudinal reinforcement ratios (s = 0.53%, 0.83%, 1.61%) and RA replacement ratios (0%, 30%, 50%, 100%). The test results indicate that the concrete shear strength diminishes by up to 30% at 100% replacement ratio compared with the natural aggregate concrete. The shear strengths of the RA concrete beams are also compared with those obtained from the existing models for natural aggregate concrete and some design considerations in using the recycled aggregate concrete are discussed.