Uniaxial tensile properties of steel fiber-reinforced recycled coarse aggregate shotcrete: Test and constitutive relationship

This paper presents the uniaxial tensile characteristics and stress-strain curves of steel fiber-reinforced recycled coarse aggregate shotcrete (SFRCAS). The study variables include concrete strength grade (C20, C30, and C40), recycled aggregate (RA) replacement ratio rg (0%, 30%, 50%, 70%, and 100%), and steel fiber (SF) volume fraction Vf (0%, 0.5%, 1%, 1.5%, and 2%). The experimental results demonstrate that the uniaxial tensile failure process of SFRCAS can be divided into three stages. The cohesiveness of concrete is improved with an increase in strength grade. However, the ratio of tensile to prismatic compressive strength stays constant at approximately 0.07. Adding Vf from 0% to 2% enhances the restraint of micro-cracking within the concrete by the SF. This leads to a significant increase of up to 120% in the uniaxial tensile strength. Furthermore, the stress-strain curve exhibits improved ductility, enhancing the toughness of SFRCAS. Based on the experimental results, empirical segmented constitutive models of Guo and single-parameter constitutive models of Sargin are fitted for SFRCAS. These constitutive models effectively predict the stress-strain behavior of SFRCAS, and the recommended formulas for model parameter calculation exhibit high accuracy. The research findings are essential for the design and detailed analysis of SFRCAS structures.