This paper presents a systematic study on the feasibility of using recycled tyre polymer (RTP) fibres for mitigating the damage of concrete induced by elevated temperatures. A series of tests were conducted to investigate the effect of RTP fibres on mechanical and thermal behaviour, pore pressure build-up and microstructural evolution of concrete exposed to elevated temperatures (20, 105, 250, 400 and 600 °C), based on which the mechanism of RTP fibres in mitigating damage of concrete was explored. Results indicate that the addition of RTP fibres effectively prevented pore pressure accumulation and significantly mitigated damage of concrete at high temperatures as the melting of RTP fibres and thermal incompatibility between RTP fibres and concrete promoted the formation of interconnected pore-microcrack network of concrete. RTP fibre was proved as a promising sustainable alternative to manufactured polymer fibres for enhancing high temperature and fire resistance of concrete. The optimal RTP fibre content was 1.2 kg/m3 considering the damage mitigation efficiency and strength loss
