Effect of PVA-steel fiber on the flexural performance of high-strength recycled aggregate concrete beams

To study the flexural performance of fiber reinforced high-strength recycled aggregate concrete beams (FRHRACB), four-point flexural experimental investigates of eight concrete beams were completed. The main parameters were coarse aggregate types, types of fiber, fiber mixing methods and volumetric fiber dosage. The influences of different parameters on the failure modes, crack width, deflection, crack load, flexural capacity and ductility of recycled coarse concrete beams were analyzed. The experimental results show that the failure modes of recycled aggregate concrete beams with or without fiber are similar to those of natural aggregate concrete beams, which have an elastic stage, a working stage with cracks and a failure stage. The cracking load, stiffness and deformation performance of recycled aggregate concrete beams are lower than those of natural aggregate concrete beams. Furthermore, wider cracks and bigger deflection are found for recycled concrete beams. With the addition of polyvinyl alcohol/steel fibers, the generation and further expansion of cracks in recycled aggregate concrete beam are restrained. Meanwhile, the cracking load is increased, and the deformation performance is enhanced. Single-mixed polyvinyl alcohol fibers have obvious positive influence on the cracking load and ductility of recycled aggre-gate concrete beams, but almost no effect on the flexural capacity. However, single-mixed steel fibers and mixed polyvinyl alcohol-steel fibers improve the flexural performance of recycled aggregate concrete beams significantly. Compared with the recycled aggregate concrete beams without fiber, when 0.1vol% polyvinyl alcohol-1.5vol% steel fiber are added, the cracking load, the flexural capacity and ductility are improved by 60.0%, 4.2% and 20.1%, respectively. According to the standard, the flexural bearing capacity of recycled aggregate concrete beams was calculated, and the calculation results agree well with the test results. © 2022, Editorial Office of Acta Materiae Compositae Sinica. All right reserved.