Constitutive modeling and extended performance evaluation of concrete reinforced with non-hybrid waste tire steel fibers

This paper investigates the extended performance and constitutive modeling of waste tire steel fiber reinforced concrete (WFRC), making notable contributions to civil engineering materials. The study assesses constitutive modeling, reinforcement indices, and the long-term performance of concrete reinforced with varying percentages of waste tire steel fiber (WSF) ranging from 0.30 % to 1.75 %. A modified analytical model for predicting compressive stress-strain curves of WFRC is introduced and compared with previous analytical models for fiber-reinforced concrete. Additionally, a novel waste tire steel fiber reinforcing index, based on WSF properties, is proposed. Empirical relationships between strength properties and reinforcement indices are established. Experimental strength properties at the standard age, as well as water absorption, carbonation depth, and split-tensile strength of specimens aged beyond the standard age at 600 days and fiber-matrix interaction obtained by SEM analysis, are reported. Prediction models are proposed for estimating the mechanical properties of WFRC at the standard age, with results compared against existing codes. The proposed modified analytical model for the uniaxial compressive stress-strain curve demonstrates better coherence with experimental curves than existing models. Furthermore, empirical equations developed in terms of the waste tire steel fiber reinforcing index demonstrate satisfactory alignment between predicted and experimental strength properties. Significant improvements are observed in specimens aged 600 days, indicating the promising role of WSF in enhancing the long-term performance and serviceability of structures. Further studies are recommended to explore the performance of WFRC in aggressive environmental conditions.