As one of the most prevalent safety risks faced by modern building structures, fire can lead to elevated spalling failure of UHPC, resulting in rapid loss of load-bearing capacity, posing significant challenges to the serviceability, lifespan, structural stability, and safety of structural engineering. Conducting relevant research holds practical application value in pushing the limits of UHPC materials and structures in terms of elevated resistance and fire prevention capabilities. The main conclusions of this paper are as follows: 1) At elevated temperatures, the strength of UHPC is primarily influenced by factors such as its strength grade, temperature, cooling method, raw material composition, moisture content, reinforcement or fiber type, and specimen dimensions. As the temperature increases, the compressive strength, flexural strength, tensile strength, and bond strength of UHPC decrease, with the loss of strength exhibiting distinct trends within different temperature ranges. 2) At elevated temperatures, UHPC undergoes phenomena such as evaporation and diffusion of pore water, deterioration of pore structure, decomposition of C-S-H gel, and failure of the interfacial transition zone, which initiate the formation of microcracks and accelerate their propagation. 3) Regarding the spalling behavior of concrete at elevated temperatures, scholars have proposed theories including the vapor pressure theory, thermal stress theory, and thermal cracking theory. While these theories can, to some extent, explain the degradation mechanisms of ordinary concrete in extreme temperature environments, they remain controversial, particularly when applied to UHPC.

Despite the extensive research conducted by scholars worldwide on UHPC in the context of building fires and elevated environments, as well as the significant achievements made in experimental and theoretical analyses of fire resistance for concrete materials or structures, the current literature reveals a lack of effective technical measures to enhance the elevated resistance of UHPC, necessitating further in-depth investigation. This field is plagued by numerous critical issues that urgently require research and resolution: 1) The elevated environment inevitably exerts negative effects on the performance of UHPC, and the enhancements achieved through existing research on improving the thermal resistance remain insufficient. It is thus imperative to develop novel intelligent elevated-resistant concrete that can efficiently prevent, resist, and insulate heat, while also integrating rapid fire warning response capabilities, through advancements in concrete material composition design, mix proportion optimization, and structural directional control. 2) At elevated temperatures, UHPC undergoes simultaneous processes of secondary hydration enhancement from unhydrated cement particles and elevated degradation of hydrated product phases. The key to deeply analyzing and comprehensively understanding the degradation mechanisms of UHPC at elevated temperatures lies in achieving in-situ microscopic characterization of hydrated product phases and accurately quantifying the contribution ratios and development patterns of these two processes to the strength of UHPC. 3) The spalling behavior of UHPC at elevated temperatures is complex and multidisciplinary. The current theories on elevated failure can only partially explain the elevated degradation of UHPC, making it difficult to predict the randomness and uncertainty of UHPC's elevated peeling and establish a correlation mechanism. It is crucial to comprehensively explore the elevated failure mechanisms of UHPC by integrating multiple disciplines such as material mechanics, thermodynamics, fracture mechanics, and blast dynamics.