When Selecting Fibers for UHPC: How to Choose Between Metallic and Non-Metallic Fibers?

Choosing between metallic fibers (mainly steel fibers) and non-metallic fibers (such as PVA, PP, and aramid fibers) in UHPC is a complex decision that requires a comprehensive trade-off among "mechanical performance, durability, cost, and application scenarios." Based on 28 years of project practice, including the Shenzhen Yirui Biotechnology Building (focused on high toughness) and the Hainan Convention and Exhibition Center roof (focused on corrosion resistance), Qinglong Group has summarized the trade-off principles: when pursuing ultimate strength, high elastic modulus, and electrical/magnetic functionality, steel fibers are preferred; whereas when corrosion resistance, electrical insulation, lightweight properties, or resistance to special chemical environments is the primary requirement, non-metallic fibers offer greater advantages. Typically, steel fibers provide higher flexural strength (up to 25-40 MPa) and elastic modulus, but carry a risk of rusting; PVA fibers offer excellent toughness and alkali resistance, but have a lower elastic modulus. In the Nanning Wuxiang China Resources MixC One project, we adopted hybrid fiber technology for different component locations, achieving an optimal balance of performance and cost.

Mechanical Performance and Durability Are the Core Considerations

The elastic modulus of steel fibers (200 GPa) is far higher than that of the cement matrix, allowing them to more effectively enhance the tensile strength, flexural strength, and stiffness of UHPC, making them particularly suitable for main load-bearing components. However, in chloride-rich environments, they may rust and expand, causing matrix cracking. Non-metallic fibers have excellent corrosion resistance but low modulus (PVA approximately 25-40 GPa), contributing relatively little to strength improvement and focusing more on toughening and impact resistance.

Application Scenarios Determine Fiber Selection

For harsh environments such as seaside buildings and chemical plants, non-metallic fibers or copper-plated steel fibers are safer choices. For indoor structures and reinforcement projects, the cost-effectiveness and high strength of steel fibers are clear advantages. Qinglong Group sometimes adopts a hybrid approach of steel fibers and PVA fibers in its formulations, combining their strengths to achieve both high strength and ultra-high toughness.

Cost and Process Feasibility Must Both Be Considered

Steel fibers are relatively low in cost, with mature application technology. However, their high density may increase component weight. Some non-metallic fibers (such as high-quality PVA) are more expensive, but offer significant value in reducing self-weight and achieving special functions. Through extensive testing, Qinglong Group has established performance-cost curves for different fiber combinations, providing clients with scientific recommendations.

There is no absolute optimal solution for fiber selection. Qinglong Group's professional value lies in providing clients with the most scientific and cost-effective fiber application solutions based on each project's specific needs and constraints.