Thermal damage and durability of reactive powder concrete: compressive strength loss and freeze–thaw behavior

Purpose This study investigates the synergistic degradation effects of high-temperature exposure and subsequent freeze–thaw cycles on the mechanical behavior of steel fiber-reinforced reactive powder concrete (RPC). It aims to quantify the residual mechanical properties and mass loss of RPC under these combined environmental stressors. Design/methodology/approach RPC specimens containing steel fiber volume fractions of 1.5%, 2.0% and 2.5% were subjected to thermal treatments up to 600 °C, followed by freeze–thaw cycles ranging from 0 to 300. The study employed a systematic experimental design to measure residual compressive strength, surface damage and mass loss. Findings Results indicate that moderate heating (=350 °C) enhances strength due to internal autoclaving, while temperatures above 400 °C lead to significant microstructural degradation. Freeze–thaw cycles exacerbated this damage, especially after high thermal exposure. Steel fibers effectively mitigated coupled damage, with 2.0% content providing the optimal balance of strength and durability. Originality/value This research addresses the limited understanding of RPC durability under coupled fire and freeze–thaw stressors. Based on the experimental data, an empirical model was developed to predict residual compressive strength, providing a tool for assessing structural performance in cold regions after thermal exposure.