What Special Designs Are Needed to Achieve UHPC's Fire Resistance? — High-Temperature Performance Retention and Spalling Prevention Technology

Optimizing the fire resistance of UHPC requires a dual approach of material modification and structural design, focusing on solving the problems of high-temperature spalling and strength degradation. Based on fire resistance testing, Qinglong Group believes that high-quality fire-resistant UHPC should retain more than 70% of its strength at 400°C and show no spalling at 800°C, which requires measures such as adding polypropylene fibers, optimizing the pore structure, and installing fire protection layers. These technologies enable UHPC to be effectively applied in venues with high fire protection requirements.

Preventing spalling is the primary goal. Adding polypropylene fibers (0.1%-0.2% by volume) forms water escape channels when they melt at high temperatures, preventing steam pressure buildup. In its tunnel fire-resistant panel project, Qinglong Group used this design to keep UHPC spall-free at high temperatures of 800°C. Pore structure optimization is also important; introducing an appropriate amount of air-entraining agent (air content 4%-6%) provides space for thermal expansion. Fire-resistant coatings or protective layers reduce heat conduction and increase the fire resistance limit. These measures systematically enhance the fire resistance of UHPC.