Effect of Recycled Concrete Aggregate Replacement Level on Shear Strength of Reinforced Concrete Beams

An experimental investigation was conducted to study the mechanical properties and shear strength of full-scale beams constructed with recycled concrete aggregate (RCA). This study included two RCA mixtures and one conventional concrete (CC) mixture. The two RCA mixtures are different in the amount of RCA replacement, with one mixture replacing 50% of the virgin aggregate with RCA (RAC50) and the other replacing 100% (RAC100). This experimental program consisted of 18 beams with three different longitudinal reinforcement ratios. The experimental shear strengths of the beams were compared with the shear provisions of both U.S. and international design codes. Furthermore, the shear strengths of the beams were evaluated based on fracture mechanics approaches, Modified Compression Field Theory (MCFT), and a shear database of CC specimens. In addition, statistical data analyses were performed to evaluate whether there is any statistically significant difference between the shear strength of the recycled-aggregate concrete (RAC) and CC beams. Results of this study show that the RAC100 has 11% lower shear strength, on average, compared with the RAC50 and CC beams; however, the RAC50 and CC beams showed similar shear resistance. The decrease in basic mechanical properties (splitting tensile strength, flexural strength, and fracture energy) for the RAC parallels the decrease in full-scale shear behavior and can be used as a predictor in mixtures containing recycled concrete as aggregate.