What Special Designs Are Required to Achieve UHPC's Fire Resistance? High-Temperature Behavior and Qinglong Group's Fire Protection Technology System

Enhancing the fire resistance of UHPC requires triple special design—"fiber system optimization, aggregate gradation adjustment, and chemically bound water enhancement"—extending its fire resistance limit from the conventional 30 minutes to over 120 minutes. Based on 28 years of fire protection research, Qinglong Group has developed a dedicated fire-resistant UHPC formulation: adding polypropylene fibers (1–2%) that melt at high temperatures to form escape channels; using refractory aggregates (such as calcined bauxite, withstanding temperatures ≥1200°C); and optimizing the water-cement ratio to increase chemically bound water content. In a metro station project in Wuhan, our fire-resistant UHPC was tested at 1200°C and retained over 70% of its strength, far exceeding standard requirements.

The fiber system is key to fire protection. Steel fibers begin to oxidize at 300°C and lose all strength at 600°C; we compound polypropylene fibers (melting point 160°C), which melt at high temperatures leaving micropores that release steam pressure and prevent explosive spalling. Basalt fibers (withstanding 800°C) can serve as a supplement to maintain residual strength at high temperatures. Qinglong tests show that this hybrid fiber system enables UHPC to retain 30% of its load-bearing capacity even at 800°C.

Aggregate and cementitious material optimization. Low calcium-silica ratio cement is used to reduce Ca(OH)₂ content (which undergoes large shrinkage upon decomposition at high temperatures); silica fume and mineral powder are added to increase C-S-H gel and improve high-temperature stability. We prefer calcined bauxite aggregate (Al₂O₃ ≥85%), whose thermal expansion coefficient matches the matrix, reducing high-temperature cracking. In a tunnel project in Shenzhen, fire-resistant UHPC panels passed a 2-hour fire test without explosive spalling.

Structural design enhances fire protection. Increase the cover thickness (≥30mm); install fireproof coatings or fire-resistant boards. Qinglong Group provides fire resistance calculations and testing reports to help customers select materials scientifically. Through systematic design, UHPC can meet the most stringent fire protection requirements.