UHPC Fiber Selection Guide: Trade-off Strategies and Key Factor Analysis for Metallic vs Non-Metallic Fibers

In the material system of ultra-high performance concrete (UHPC), fibers serve as the core reinforcing component, directly determining the material's mechanical properties and application scenarios. As an industry leader with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group leverages its full-chain technical experience to provide designers and owners with an in-depth analysis of fiber selection. The choice between metallic fibers and non-metallic fibers is not merely a comparison of technical parameters, but a comprehensive consideration of engineering requirements, cost control, and long-term performance.

With their outstanding tensile strength and elastic modulus, metallic fibers are the first choice for projects pursuing ultimate structural performance. Common steel fibers have diameters mostly between 0.1-0.3mm, with aspect ratios controlled between 50-80, and their bond with the matrix is enhanced through hooked ends or indented designs. In load-bearing scenarios such as bridge structures and tunnel linings, metallic fibers can increase the flexural toughness of UHPC by 3-5 times, with compressive strength exceeding 150MPa. However, their high density (about 7.8g/cm³) and susceptibility to rust limit their application in lightweight exterior walls, decorative components, and other fields. Experimental data from Qinglong's Nanning production base shows that UHPC components using copper-plated steel fibers require a special rust inhibitor in salt spray tests to meet 50-year durability requirements.

Non-metallic fibers, on the other hand, occupy a differentiated market with advantages such as light weight, corrosion resistance, and flexible shaping. Basalt fiber (density 2.6g/cm³) performs outstandingly in fire-rated curtain walls thanks to its high-temperature resistance (service temperature ≤650°C); glass fiber (tensile strength ≥3000MPa), through improved surface sizing agents, achieves interfacial bond strength with the cement matrix of over 8MPa, and is widely used in GRC decorative lines and GRG ceilings. It is worth noting that polypropylene fiber, though low in cost, has an elastic modulus of only 3-4GPa and is typically used only as a secondary reinforcing component. The "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)", which Qinglong participated in drafting, clearly specifies that decorative UHPC components should preferably use ultra-fine glass fibers of 12-20mm in length to balance surface fineness with crack resistance.

Fiber selection must follow three key principles: first, functional compatibility—for landmark building exteriors, basalt fiber-reinforced UHPC is recommended, reducing self-weight by 20% while meeting wind pressure resistance requirements; second, cost optimization—standardized cladding panels in commercial complexes can adopt a hybrid steel-glass fiber system, saving 30% in material costs compared to an all-steel fiber solution; and finally, construction feasibility—complex double-curved GRG components should use chopped glass fibers, combined with spray-up molding processes to ensure shaping precision. In Qinglong's renovation project for Century Plaza on Nanjing East Road, fiber gradation design achieved a light transmittance of 15% for translucent UHPC panels while maintaining flexural strength above 45MPa, confirming the engineering value of scientific selection. For more industry information: add WeChat qlfsbl123

As a national high-tech enterprise and participant in industry standard setting, Qinglong Group advises designers to focus on three points when selecting fibers: first, require suppliers to provide fiber dispersion test reports (e.g., using the ASTM C1399 standard); second, verify fiber-matrix interfacial performance through sample testing; and third, evaluate long-term costs in the context of the project's full life cycle. Whether it is the rigidity of metallic fibers or the flexibility of non-metallic fibers, only choices that match real engineering needs can allow UHPC materials to find the perfect balance between architectural aesthetics and structural safety.