Mitigating the damage of ultra-high performance concrete at elevated temperatures using synergistic flame-retardant polymer fibres

Abstract

Ultra-high performance concrete (UHPC) is vulnerable to high temperature-induced damage due to its dense microstructure. To mitigate thermal damage of UHPC, this study develops synergistic flame-retardant polymer (SFRP) fibres by introducing organic-metallic fillers and experimentally investigates the thermal properties, compressive behaviour, and microstructural evolution of SFRP fibre reinforced UHPC subjected to elevated temperatures up to 800 °C. Results indicated that the addition of SFRP fibres can effectively prevent the explosive spalling and significantly reduce the strength loss of UHPC at high temperatures due to the thermal mismatch between fibres and concrete. SFRP fibres were also proved to help greatly enhance the fire resistance and mitigate the thermal damage of UHPC, which can be attributed to the increased connectivity of pore structure, filling effect of flame-retardant polymers, and delayed degradation of micromechanical properties. The SFRP fibre content of 2.0 vol% is recommended considering the residual strength and damage mitigation efficiency.