High temperature and freeze-thaw study of strengthened concrete with ultra-high-performance concrete

This study investigates the effectiveness of using ultra-high-performance concrete (UHPC) to strengthen concrete members subjected to high temperature and freeze-thaw conditions. Initially, the physical and mechanical properties of UHPC were examined. Subsequently, the durability of UHPC was evaluated through high temperature and freeze-thaw tests, assessing compressive strength, flexural strength, and splitting tensile strength. The study examined the reinforcing effects of different repair materials and thicknesses, including plain concrete and UHPC with varying fibre content. Results indicate that UHPC demonstrates high strength, ductility, and durability. However, under high temperature conditions exceeding 400°C for 2 hours, UHPC experienced bursting. Nonetheless, its strength remained relatively stable after 1000 freeze-thaw cycles, demonstrating excellent durability and resistance. Additionally, applying a 2-cm thickness of UHPC to strengthen concrete members resulted in significant retrofitting effects, enhancing the structural integrity of damaged buildings.