107 / 2022-04-24 17:29:05

Effect of post-fire curing on strength recovery of thermally damaged ultra-high performance concrete

Post-fire curing,Physicochemical changes,ultra-high performance concrete

Post-fire curing is a promising approach for recovering the properties of fire-damaged concrete. This study investigates the effects of post-fire water and CO₂ (40-90% cycled relative humidity and 20% CO₂) on the strength recovery and physicochemical changes of thermally damaged ultra-high performance concrete (UHPC). The UHPC samples were subjected to elevated temperatures up to 1000 °C and experienced recuring for 30 days. Multiple characterization methods, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and energy-dispersive X-ray spectrometry (EDX), were utilized to identify the phase change, microstructure, and porosity of the UHPC samples. The results show that the recovered compressive strength can even surpass their original compressive strength after 600 and 800 °C exposure and recuring. A high silica content is unfavorable for strength recovery because the calcium silicates formed have low reactivity. After 1000 °C exposure, carbonation is needed for strength recovery. The reactivity of the products after heat exposure determines the degree of healing and the strength recovery primarily depends on filling of the microcracks.