Performance recovery of high-temperature damaged ultra-high-performance concrete under different curing environments

The self-healing capability and susceptibility to salt solution erosion in ultra-high-performance concrete (UHPC) significantly influence the mechanical properties and long-term durability of concrete structures within coastal or underground environments. Acknowledging the intricacies of real-world environments, this study focuses on UHPC that has endured high-temperature damage at 800 degrees C. The research aims to analyze the property variations within 28 days following exposure to diverse dry and wet conditions, as well as salt solution environments. The findings demonstrate a substantial recovery in both mechanical and transport properties of the hightemperature-damaged UHPC, attributed to its inherent self-healing capability. Among the dry and wet conditions, the optimal performance recovery of UHPC specimens is observed when they are subjected to submerged and immersed environmental conditions. Furthermore, when immersed in a salt solution environment, the beneficial impacts attributed to the self-healing property tend to outweigh the detrimental effects of salt solution erosion. All scenarios exhibit a trend of enhanced properties, with the presence of chloride salts being particularly conducive to the recovery process. However, exposure to a sulfate-rich environment induces deterioration in transport properties and pore structure, resulting in a partial incongruity with the mechanical property results. Microscopic analysis techniques reveal that the primary contributors to enhanced properties encompass a range of hydration products formed due to the interaction between water, salt solutions, and the compromised UHPC. Nevertheless, owing to the intricate nature of the environment, disparities arise in both the type and quantity of hydration products, contributing to variations in the extent of property alterations.