Bond Behavior of Recycled-Fiber Recycled Concrete and Reinforcement

Abstract

Recycling solid construction waste is an inevitable trend to be followed for the realization of sustainable economic development. The bond behavior of reinforcement and recycled-fiber recycled concrete is discussed in this paper based on the observations of a half-beam unidirectional pullout test. With different recycled aggregates replacement ratios and recycled fibers volume content as variables, the pullout behavior, ultimate bond stress, and bond-slip under monotonic loading are evaluated. The test comprises two parts: direct pullout test and pullout test after the attachment of strain gauges inside the reinforcement. The results show that the half-beam unidirectional pullout test can suitably reflect the bond performance between recycled-fiber recycled concrete and reinforcement. The replacement rate of recycled aggregates exhibits a significant effect on the bond behavior between reinforcement and concrete, and the bond stress reduces by 36.92% when the replacement ratio is 100%. Adding recycled fibers is proposed to improve the bond behavior between recycled concrete and reinforcement; more specifically, the addition of 0.12% recycled fibers can increase the bond stress by 11.34% when the replacement ratio of the recycled aggregates is 50%. Moreover, the bond-slip curve relationship model between recycled-fiber recycled concrete and reinforcement that suitably correlates with the experimental results is established. Finally, the bond stress distribution is nonuniform. With the increase in the pullout force, bond stress causes local stress concentration. The more recycled aggregates, the speedier the bond stress transfer; furthermore, a moderate amount of recycled fiber can alleviate the stress concentration phenomenon. This research proposes a novel method of bond behavior test; furthermore, a novel recycled-fiber recycled concrete material is proposed that could be utilized in actual construction, and the recommended dosages are provided.