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This paper investigates the flexural and shear behavior of reinforced concrete beams that use recycled concrete aggregates (RCA) as replacement for coarse natural aggregates (e.g., crushed stone, gravel). The experimental results from 12 twin pairs of normal strength concrete beam specimens are presented and compared with predictions from existing code methods and analytical models for conventional concrete. Each pair of beams is saw-cut from a single, longer member to investigate the inherent variability in the results, specifically focusing on locally available recycled materials with minimal processing and construction methods that are consistent with current U.S. practice. It is found that the use of RCA does not cause an observable change in the progression of nonlinear behavior and failure. The effect of RCA on the flexural and shear strength of the beams is also small; however, there is a considerable reduction in the initial stiffness and an increase in the ultimate flexural deflections as the amount of RCA is increased. In general, the predicted results are reasonably close to the measured trends, indicating that existing analytical models and code-based procedures for conventional concrete can also be applied to RCA concrete beams.
Knaack et al. (Tue,) studied this question.