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

Fiber selection is a key step in UHPC mix design. Metallic and non-metallic fibers each have their own advantages, and the choice must be made according to specific project requirements. Correct fiber selection can significantly improve the overall performance of UHPC.

In the curved curtain wall project of the Wuhan Han Show Theatre, Qinglong UHPC adopted a hybrid reinforcement scheme of copper-plated steel fiber and PVA fiber: steel fiber (0.2mm in diameter, 13mm in length) provides the primary reinforcement, while PVA fiber (0.04mm in diameter, 12mm in length) improves early-age crack resistance. This combined use achieved a flexural strength of 25MPa while reducing surface plastic cracks.

Advantages of Metallic Fibers

Steel fiber has a tensile strength ≥2000MPa and an elastic modulus of 200GPa, with a significant reinforcement effect. However, it has high density, is prone to corrosion, and conducts electricity and heat strongly.

Characteristics of Non-Metallic Fibers

PVA fiber has a tensile strength ≥1500MPa, strong alkali resistance, and low density. However, its elastic modulus is relatively low (40GPa), and its reinforcement effect is limited.

Hybrid Use Scheme

Steel fiber is used as the primary fiber (2% volume fraction), with PVA fiber as a supplement (0.5% volume fraction). This ensures the reinforcement effect while improving workability and durability.

Selection Considerations

Consider load type, service environment, durability requirements, cost factors, etc. Important structures should primarily use steel fiber, while non-metallic fibers may be selected for special environments.

Fiber selection requires comprehensive consideration, and the optimal solution should be determined through experimental verification when necessary.