Postcracking tensile behavior of blended steel fiber-reinforced concrete

Fiber blends have the potential to improve the mechanical and sustainability credentials of steel fiber-reinforced concrete (SFRC), but at which ratios these can work is not known a priori. This paper investigates the uniaxial tensile stress–strain (σ − ε) relationship of blended SFRC using manufactured steel fibers on their own, or blended with sorted steel fibers recycled from end-of-life tires (recycled tire steel fiber [RTSF]), at total fiber dosages of 30, 35, and 45 kg/m3. The accuracy of two σ − ε relations proposed by RILEM TC 162-TDF and Model Code 2010 is assessed using the experimental results from concrete prisms. By using nonlinear finite element (FE) analysis, it is found that the RILEM approach can lead to significant overestimation (up to 72%) of peak flexural load and energy absorption capacity (up to 39%), while the Model Code 2010 can provide a rather accurate prediction of the energy absorption capacity and some overestimation (less than 34%) of the peak flexural load. Inverse FE analysis is used to determine indirectly the uniaxial tensile σ − ε relations of the examined SFRC mixes, and a simplified trilinear relation for SFRC is proposed. It is concluded that the tensile strength of SFRC with RTSF at a low total fiber dosage is only marginally improved by fiber addition, and the postcracking tensile strengths at different strains can be determined directly from residual flexural tensile strengths (fRi) of prisms.