Shear performance of recycled aggregate concrete beams: An insight for design aspects

The shear failure of reinforced concrete beam is a brittle type of failure and can be dangerous if it is not properly designed. The inherent inferior quality of recycled coarse aggregate (RCA) makes the recycled aggregate concrete (RAC) beams even more vulnerable in shear resistance. This persuades the structural designers to account each of the contributing components in the shear resistance mechanisms seriously, especially that of concrete. In this regard, an experimental investigation was carried out on fourteen beams to examine the shear performance of RAC beams in the absence and presence of transverse reinforcement. Six numbers of beams without transverse reinforcement were tested to examine the contribution of RAC in shear resistance mechanisms and eight beams with shear reinforcement were tested to verify the applicability of the prevailing shear design provisions for RAC beams. The inferior mechanical properties of the RAC are improved satisfactorily by implementing the Particle Packing Method of mix design approach along with the established Two Stage Mixing Approach. However, even with the improved mechanical properties of RAC, the poor performance of RAC beams in shear could not be avoided and a drop of 14% was recorded in the ultimate shear strength of RAC beams without stirrups. A database is prepared by compiling the reported test results of RAC beams with and without transverse reinforcement. An alternative equation is proposed to predict the diagonal tension cracking strength of RAC beams, by using the database of RAC beams without transverse reinforcement and it exhibits a better correlation with the experimental results. Further, in the shear resistance mechanisms of RAC beams the effectiveness of stirrups is studied using the database of RAC beams without and with transverse reinforcement.