High-temperature resistant sprayed UHPC based on PC-CAC-C$ system

Fire exposure remains a critical challenge in civil engineering disaster prevention, posing a significant and unavoidable threat to modern structural systems. Repair materials should be capable of delivering high-strength structural support within hours following fire exposure, while exhibiting adequate thermal resistance to ensure the safety of both occupants and the structural system. Sprayed ultra-high-performance concrete (SUHPC) exhibits high strength and excellent durability, along with the advantage of rapid placement on complex geometries. These characteristics make it a promising candidate for use in rapid repair applications. However, the development of SUHPC still faces several critical challenges that require urgent improvement, including early-age performance (such as rheological behavior and early strength), later-age mechanical properties, and spalling resistance after high-temperature exposure. Building upon previous investigations into binder optimization and high-temperature performance of UHPC, this thesis develops a novel SUHPC incorporating a PC–CAC–C$ ternary binder system. The proposed SUHPC simultaneously achieves excellent early-age properties, improved later-age mechanical performance, and enhanced resistance to explosive spalling under elevated temperatures. The research framework of this thesis consists of two main parts: Part I focuses on binder optimization and high-temperature performance of UHPC, while Part II extends these findings to the design and development of a spalling-resistant SUHPC.