This study investigates the thermomechanical behavior of cement pastes reinforced with recycled steel fibers (RSF) recovered from discarded tires, focusing on their response to uniaxial compression at elevated temperatures. As sustainable construction materials become increasingly important, understanding the interaction between fiber reinforcement and thermally induced degradation is essential for designing resilient cementitious systems. A comparative evaluation was conducted using mixtures reinforced with RSF and hooked-end synthetic steel fibers (SSF). The experimental program examined the evolution of key mechanical properties, including modulus of elasticity, compressive strength, and strain at peak stress, across fiber dosages ranging from 0 to 1.0% (vol.) and exposure temperatures of 22, 300, and 500 °C. A multivariate regression framework was subsequently developed to predict normalized mechanical responses as functions of fiber type, dosage, and temperature, and yielded high predictive accuracy ( R 2 = 0.983 for modulus of elasticity, 0.958 for compressive strength, and 0.942 for peak strain). The results suggest that thermal exposure induces significant degradation in stiffness and strength due to microstructural damage, while simultaneously increasing deformation capacity. Fiber reinforcement alters the failure mechanism by enhancing crack bridging and delaying localization. Under ambient conditions, variations in modulus of elasticity among mixtures remain within a narrow range (25.8–26.5 GPa), which indicates no statistically substantiated improvement attributable to RSF, given the absence of formal significance testing and the magnitude of typical experimental variability. However, under elevated temperatures, RSF-reinforced mixtures exhibit comparatively improved strain capacity and toughness relative to SSF systems. Overall, RSF contributes primarily to improved ductility and energy absorption rather than stiffness enhancement. The proposed predictive model effectively captures the coupled influence of temperature and fiber characteristics on normalized mechanical behavior, therefore, provides a reliable tool for assessing thermally exposed fiber-reinforced cementitious systems.
Alsaif et al. (Thu,) studied this question.