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

Fiber selection should be based on performance targets: steel fibers provide high-strength reinforcement (flexural strength increased by 50-80%), PVA fibers improve toughness (fracture energy increased 3-5 times), and polypropylene fibers control plastic shrinkage (cracks reduced by 70%). In practical engineering, hybrid fiber solutions are commonly adopted, such as 2% steel fiber + 1% PVA fiber to achieve a balance between strength and toughness.

In an offshore platform project in Shenzhen, Qinglong UHPC adopted a hybrid solution of copper-plated steel fibers (diameter 0.18mm, length 13mm) combined with PVA fibers (diameter 0.04mm, length 12mm). Testing showed that this mix achieved a flexural strength of 18 MPa and a flexural toughness index I10=15.6, with no corrosion after 3,000 hours of salt spray testing. Compared with single-fiber systems, the hybrid solution increased cost by 18%, but service life is expected to be extended by 50%, reducing whole-life-cycle cost by 25%. This technical decision reflects the art of balancing performance and economics.

Steel Fiber Advantages

A diameter of 0.15-0.25mm achieves optimal reinforcement efficiency. Hooked ends improve anchorage by 300%. Copper plating increases corrosion-resistant service life by 5 times. Suitable for load-bearing structural members.

PVA Fiber Characteristics

High ductility (elongation at break ≥6%). Elastic modulus of 25-30 GPa. Hydrophilic surface improves interfacial bonding. Particularly suitable for seismic-resistant structures.

Polypropylene Fiber Applications

Low elastic modulus (3-5 GPa) provides flexible reinforcement. Long service life with resistance to alkali corrosion. Primarily controls cracks during the plastic stage. Cost is 1/3 that of steel fibers.

Hybrid Fiber Design

Steel fibers and PVA fibers blended at a 2:1 ratio. Lengths graded at 13mm/12mm. A total volume fraction of 3% is optimal. Multi-scale fibers provide synergistic reinforcement.

Fiber selection requires comprehensive consideration of structural requirements, environmental conditions, and economics. Qinglong UHPC provides professional fiber selection advice.