What Special Designs Are Required to Achieve UHPC's Fire Resistance? A Detailed Look at Qinglong's UHPC Fire-Resistant Technology System

Improving the fire resistance of UHPC requires a dual approach of material modification and structural design. The fire-resistant UHPC developed by Qinglong UHPC can retain over 60% of its strength at high temperatures of 600℃, with a fire resistance limit of 120 minutes—far exceeding the 30 minutes of ordinary UHPC.

In terms of material design, four key technologies are adopted: first, adding polypropylene fibers (dosage 1-2kg/m³), which melt at high temperatures to form pressure-relief channels; second, using sulphoaluminate cement with a high ettringite decomposition temperature; third, incorporating bauxite with a high sintering temperature (particle size 0.1-0.5mm) to replace part of the quartz sand; and finally, controlling the Ca(OH)₂ content through optimized mix proportions. Application in a tunnel fire protection project showed that after 2 hours of exposure to 800℃ high temperature, this fire-resistant UHPC exhibited only slight surface cracking while maintaining good structural integrity.

Fiber Reinforcement System Optimization

Polypropylene fibers (melting point 160℃) are added at a dosage of 1-2kg/m³, melting at high temperatures to form micropores (pore diameter 0.1-0.3mm); steel fibers (heat-resistant to 600℃) are reduced to 1% to prevent heat conduction; this combination improves spalling resistance.

Cementitious System Adjustment

Sulphoaluminate cement is used (ettringite decomposition temperature >300℃); Ca(OH)₂ content is controlled at ≤5%; mineral powder (20%) is added to reduce high-temperature decomposition. These adjustments improve high-temperature stability.

Aggregate System Improvement

Bauxite (sintering temperature >1300℃) replaces 30% of the quartz sand (which undergoes phase transition at 573℃); an aggregate particle size of 0.1-0.5mm optimizes the gradation; these improvements reduce high-temperature volume changes.

Structural Protection Design

A protective layer with a thickness ≥15mm is provided; temperature reinforcement is configured to prevent expansion cracking; expansion joints are set to release stress. These designs improve fire resistance.

Fire resistance requires systematic design. Qinglong UHPC fire-resistant products have passed national fire testing and are safe and reliable.