Shear strength of 50 MPa longitudinally reinforced concrete beams made with coarse aggregates from low strength recycled waste concrete

Crushed waste concrete is a viable source of recycled coarse aggregates (RCA) to produce concrete. The RCA generally has less favorable properties relative to natural coarse aggregates (NCA), which can affect the shear strength of the concrete. This paper reports the results of an experimental study of the shear behavior of seven shallow longitudinally reinforced beams containing seven ercentages of replacement (PR) of NCA with RCA ranging from 0 to 100%. The target cylinder compressive strength (f(cyl)) of the concrete was 50 MPa and the longitudinal reinforcement ratio (rho(L)) was about 1%. The results indicate that all the beams failed in shear. The use of RCA did not change their mode of failure and did not directly affect the characteristics of the critical diagonal failure cracks. In addition, it was found that, on average, the recycled aggregate concrete (RAC) beams had a normalized shear strength that was 12% higher than that of the natural aggregates concrete (NAC) control beam. The difference in strength amongst the RAC beams with various PR was also limited. It is to be noted that the literature reports numerous cases where the RAC beams resisted higher strengths than their NAC control beams. Finally, the observed ultimate strengths of the beams were compared to the shear strength calculations of the ACI, CSA, EC2, and MC2010 codes and the Modified Compression Field Theory (MCFT). The calculated strengths were found to be conservative for the RAC beams. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study investigated the shear behavior of concrete beams containing recycled coarse aggregates (RCA), finding that the use of RCA did not change the mode of failure or directly affect critical diagonal failure cracks. The recycled aggregate concrete (RAC) beams had higher normalized shear strength compared to natural aggregates concrete (NAC) beams, with a limited difference in strength amongst the various percentages of replacement (PR). Calculated strengths based on various codes were found to be conservative for the RAC beams.