Performance analysis of fiber reinforced recycled aggregate concrete at elevated temperatures using response surface methodology

Abstract

Abstract The increasing risk of fire hazards and the environmental burden of construction and demolition (C&D) waste necessitate sustainable, fire-resistant building materials. This study investigates the potential of recycled aggregate concrete (RAC) reinforced with fibers to enhance high-temperature performance while promoting waste utilization. In the first phase, concrete mixtures with 0%, 25%, and 50% recycled aggregate (labeled RAC00, RAC25, and RAC50) were evaluated at 23 °C, 300 °C, and 600 °C. RAC00 exhibited a 16% reduction in compressive strength at 300 °C and over 50% at 600 °C. While RAC25 initially showed a 10–30% decrease compared to conventional concrete at room temperature, it exhibited only a 1% strength decline at 300 °C and a 28% reduction at 600 °C, making it the most effective composition for further study. In the second phase, steel fibers (SF) and polypropylene fibers (PPF) were incorporated into RAC25, yielding substantial tensile strength improvements: RAC25-SF increased by 5.6% at 23 °C, 24.8% at 300 °C, and 28.3% at 600 °C. RAC25-PPF showed a 12.5% increase at 23 °C but declined at higher temperatures, with a 9.9% decrease at 300 °C and 32.9% at 600 °C. SF enhanced strength across all temperatures, while PPF reduced performance above 200 °C. Fiber additions improved ductility, toughness, and moisture retention, mitigating crack propagation under heat. Statistical modeling using ANOVA and response surface methodology (RSM) confirmed high model validity (R2 > 0.80). The study concludes that RAC25 with steel fibers offers a sustainable, heat-resistant construction material, addressing both fire resilience and C&D waste challenges.