Effect of steel-waste PET hybrid fiber on properties of recycled aggregate concrete based on response surface methodology

To investigate the combined effect of steel and waste PET fibers on the properties of recycled aggregate concrete (RAC), steel-waste PET hybrid fiber reinforced recycled aggregate concretes (HFRACs) were produced. Slump and mechanical strength tests on the samples were performed. The interaction between fiber contents and each performance index was examined by response surface methodology (RSM), and the optimal steel and waste PET fiber contents were obtained by maximizing strength indices simultaneously. The results showed that the contents of two types of fibers had a significant negative impact on workability and positive effect on mechanical strength except the compressive strength which was not significantly affected by the PET fiber content. The slump and compressive strength of HFRAC can be predicted by linear equations with the contents of steel and waste PET fibers, while the splitting tensile strength and flexural strength can be predicted by quadratic polynomial equations. Waste PET fiber properly combined with steel fiber can improve the mechanical properties of RAC, which illustrates steel-waste PET HFRAC has the potential to be green sustainable concrete.