Effect of multi-composite hybrid fiber on cyclic compression performance of recycled concrete

In order to study the effect of multi-composite hybrid fiber on the cyclic compression behavior of recycled concrete (HFRAC), monotone compression tests and monotone cyclic compression tests were carried out on 84 specimens. The effects of steel-carbon fiber (SF-CF), steel-glass fiber (SF-GF), steel-polypropylene fiber (SF-PF) and steel-polyvinyl alcohol fiber (SF-PVA) on the cyclic compression properties were analyzed. The results show that compared with ordinary recycled concrete, the failure mode of HFRAC is ductile failure, the envelope of stress-strain curve of HFRAC specimens under cyclic compression is approximately consistent with the stress-strain curve under monotonic compression, and the inhibition effect of SF-GF hybrid fiber and SF-PVA hybrid fiber on plastic strain accumulation is better than that of steel fiber recycled concrete. The addition of SF-CF hybrid fiber with large elastic modulus plays a significant role in increasing the stiffness degradation rate and hysteretic energy dissipation capacity of recycled concrete, and the stiffness degradation rate of recycled concrete increases by 43.4% when 1.0vol%SF+0.5vol%CF was added. Finally, on the basis of the experimental results, the full curve equation of stress-strain relationship of HFRAC under uniaxial cyclic compression is established, and the calculated results are in good agreement with the experimental results.