High-temperature performance of recycled brick aggregate concrete with modified rubber and recycled tire steel fibers: Mechanical behavior and damage mechanisms

The application of recycled tire steel fibers (RTSF) in recycled brick aggregate concrete (RBAC) has considerable potential; however, research on its high-temperature performance is relatively limited. To explore the resource utilization of waste tires in RBAC, this study employed an environmentally friendly pretreatment method to incorporate rubber particles (RP) and RTSF into RBAC at varying dosages to balance their effects on strength. The optimal mix ratio was determined through room-temperature mechanical testing, and the performance evolution under high-temperature conditions was systematically analyzed. Macroscopic testing and microscopic analysis showed that polyvinyl alcohol (PVA) modification significantly improved the hydrophilicity of the rubber surface. RBAC with an R10S1.0 mix ratio exhibited a more moderate failure process and better ductility, with compressive and splitting tensile strengths increasing by 18.1% and 33.6%, respectively, compared to the Control group. PVA enhanced the interfacial transition zone, increasing the bond strength of RTSF by 27.2%. After high-temperature exposure, fractal dimension analysis showed that the crack network of RBAC was simpler and more ordered. In the high-temperature range of 600–800°C, the residual compressive strength of RSRBC is 34–42% higher than that of the control group. Furthermore, RSRBC exhibited superior resistance to thermal stress induced by rapid cooling, with a strength loss of only 14.3% compared to 22.6% for the control group at 800 °C, confirming its reduced cooling sensitivity and good post‑fire stability. This study provides a sustainable solution for enhancing the mechanical performance of RBAC, and promotes the efficient utilization of waste tire components.