Shear behavior analysis and capacity prediction for the steel fiber reinforced concrete beam with recycled fine aggregate and recycled coarse aggregate

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This paper mainly studies the shear behavior of steel fiber reinforced concrete beams with recycled fine aggregate and recycled coarse aggregate. A total of thirteen beams with 150 mm width, 300 mm height, and 3000 mm length were tested under four-point bending. The shear span-to-depth ratio was kept the constant of 2. The spacing of stirrups was 150 mm, 200 mm, and 250 mm, respectively. The recycled fine aggregate and recycled coarse aggregate obtained from building demolition waste were introduced in the concrete mixes with the replacement ratio of 0%, 50%, and 100%, the steel fiber volume fractions in the beams were 0%, 0.5%, 1.0%, and 1.5%, respectively. The shear capacity, the mid-span deflection, and the stirrups strain were measured in this test. The results indicated that the shear capacity of the concrete beam with recycled aggregate and steel fibers decreased with the increase in the replacement ratio of recycled coarse aggregate, and gradually improved as the increase in steel fiber volume fractions, respectively. The steel fiber volume fraction of 1.0% in concrete was almost sufficient to offset the shear capacity degradation induced by 100% recycled fine aggregate replacement ratio and 100% recycled coarse aggregate replacement ratio. Finally, the effects of recycled fine aggregate, recycled coarse aggregate, and steel fibers on the shear behavior of the concrete beams were severally quantified by the linear equations, and a model for predicting the shear capacity of concrete beams with recycled fine aggregate, recycled coarse aggregate, and steel fibers was proposed and verified.