Work

High-temperature spalling behavior and mechanical performance of ultra-high-performance seawater sea-sand concrete

Year: 2026

Type: article

Abstract: The high-temperature spalling behavior and post-fire residual properties of ultra-high-performance seawater sea-sand concrete (UHPSSC) remain insufficiently understood. In this study, high-temperature tests were conducted to investigate the effects of heating rate, oven-drying treatment, and polyvinyl alcohol (PVA) fiber content (0.1%-0.3%) on spalling behavior and residual mechanical properties after exposure to 25-800 °C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) were used to analyze microstructural and pore evolution. The results show that UHPSSC without PVA fibers is prone to severe disintegrative spalling, whereas interconnected microchannels formed after PVA fiber melting promote vapor migration and pressure release, thereby significantly inhibiting spalling. Residual compressive strength and splitting tensile strength first increase and then decrease, peaking near 400 °C and dropping to approximately 30%-40% of ambient-temperature values at 800 °C. Microscopic characterization indicates that dehydration and decomposition of hydration products are the main physicochemical factors causing strength deterioration, in which the continuous dehydration and decomposition of C-S-H and Ca(OH) 2 and the thermal instability of chloride-bearing phases such as Friedel's salt are important deterioration processes. Subsequent pore coarsening and interfacial damage further weaken matrix continuity and load-bearing capacity. The thermal evolution of Friedel's salt reflects the material-specific behavior distinguishing UHPSSC from conventional UHPC. These findings provide a basis for fire spalling risk assessment and post-fire residual performance evaluation of UHPSSC.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2026.09.160