Discussion and Analysis of the Special Designs Required to Achieve the Fire Resistance of UHPC

The Invisible Guardian of Building Safety: Six Core Design Strategies for UHPC Fire Resistance

Under the dual demands of modern architectural aesthetics and structural safety, ultra-high performance concrete (UHPC) is becoming the material of choice for landmark buildings and high-end projects thanks to its outstanding mechanical properties and design freedom. However, when UHPC is applied in high-temperature environments, how can its inherent fire resistance limit be overcome? As an industry expert with 28 years of full-chain UHPC/GRC/GRG/GRP experience, Qinglong Group will systematically explain the pathways to achieving UHPC fire resistance from three dimensions: material modification, structural optimization, and process innovation.

1. Reengineering the Fire-Resistant Genes of the UHPC Material System

The fire resistance of UHPC stems first from the scientific design of its material formula. By incorporating nano-scale alumina micro powder and high-temperature-resistant fibers, the material's initial decomposition temperature can be raised above 600°C. Through more than 2,000 mix proportion trials, Qinglong Group's R&D center found that when steel fiber volume content is controlled within the 2.5%-3% range and combined with basalt fiber to form a three-dimensional network structure, microcrack propagation at high temperatures can be effectively suppressed. This "dual-fiber synergistic reinforcement system" has passed a 120-minute fire resistance limit test in a super high-rise project in Nanning, achieving 40% longer fire resistance than conventional mix proportions.

2. Gradient Structural Design: Building Multiple Lines of Fire Defense

To meet the fire protection requirements of different building parts, UHPC components can adopt "functional gradient design". In a practical case at the Nanning production base, exterior wall cladding panels use a sandwich structure of "high-temperature-resistant surface layer + structural reinforcement layer + insulating core layer": the surface layer contains 15% metakaolin to form a fire-resistant barrier, the middle layer is hybrid-reinforced with steel fibers and PVA fibers, and the core layer incorporates aerogel insulation material. This structure keeps the temperature on the non-fire side within 140°C even under 800°C flame jet exposure, meeting the Class 1 fire resistance requirements of GB 51249-2017 "Technical Code for Fire Safety of Steel Structures of Buildings".

3. Engineering Practice of Reinforcement Optimization and Joint Fire Protection

The steel reinforcement cage hidden inside UHPC components is a key element of fire-resistant design. Qinglong's technical team innovatively adopted a combination of "epoxy-coated rebar + stainless steel tying wire", together with a design reserving a 15mm protective cover thickness, enabling the reinforcement to maintain structural integrity in a fire. In the Dongguan Women and Children's Activity Center project, fire scenarios were simulated using BIM technology, and a fire-resistant rock wool filling layer was added to the connection joints between the UHPC curtain wall and the main structure, successfully raising the joints' fire resistance limit to 90 minutes. This technology won the Silver Award of the AALBORG WHITE Cup GRC Building Engineering Innovation Award.

4. The Profound Impact of Precasting Processes on Fire Resistance

The production process directly determines the density and defect control of UHPC. The "vacuum casting + steam curing" process adopted by Qinglong Group keeps the porosity of components below 3%, significantly reducing the rate of heat transfer at high temperatures. Comparative tests show that UHPC specimens cured by autoclaving at 180°C retain 65% of their initial compressive strength at 1000°C, far higher than the 42% achieved by conventional curing. This industrialized production advantage enabled Qinglong UHPC products to achieve uniform fire resistance across 5,000 square meters of curtain wall components in a commercial complex project in Singapore.

5. A Full Life-Cycle Fire Resistance Assurance System

As a national high-tech enterprise integrating detailed design, manufacturing, and construction installation, Qinglong has established a full-chain fire resistance assurance mechanism from material R&D to after-sales maintenance. In a convention and exhibition center project in Guangzhou, the technical team embedded temperature sensors to monitor thermal stress changes in components in real time, combined with a self-developed UHPC fire resistance prediction model, providing data support for later maintenance. This "active monitoring + preventive maintenance" model keeps the project at 95% of its designed fire resistance performance five years after delivery.

6. Technology Innovation Directions Guided by Industry Standards

Experience from participating in drafting the industry standard "General Technical Requirements for Non-Load-Bearing Ultra-High Performance Concrete (UHPC) Components" shows that improving UHPC fire resistance requires cross-disciplinary integration of materials science and structural engineering. The "self-healing fire-resistant UHPC" technology being developed at Qinglong's R&D center incorporates heat-expansive microcapsules that automatically fill microcracks when the temperature exceeds 300°C; a patent application has been filed for this technology. This innovative exploration is driving UHPC's technological leap from passive fire protection to active fire protection.

From molecular-level control of material formulas to systematic solutions for engineering applications, achieving UHPC fire resistance is a perfect combination of scientific design and engineering experience. Qinglong Group's 28 years of technical accumulation show that only by integrating fire-resistant design throughout the product's entire life cycle can this high-performance material safeguard building safety while fully releasing its aesthetic expression potential. As new building materials continue to evolve, UHPC fire resistance innovation will ultimately become the balance point between building safety and design freedom.