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

The selection of fibers for UHPC should be based on comprehensive consideration of four aspects: "engineering requirements, service environment, cost control, and process adaptability". Metal fibers (mainly steel fibers) and non-metallic fibers (such as PVA, PP, and basalt fibers) each have their own advantages. Qinglong Group has summarized selection criteria from 28 years of practice: choose steel fibers when there are special requirements for strength and electrical conductivity; choose non-metallic fibers when corrosion resistance, insulation, or lightweighting is required. In the roofing project of the Hainan International Convention and Exhibition Center, copper-plated steel fibers were selected, ensuring strength while also providing corrosion resistance; whereas in the anti-static floor of an electronics factory in Shenzhen, insulating PVA fibers were chosen.

The greatest advantage of steel fibers lies in their high elastic modulus (200GPa) and tensile strength (above 2000MPa), which can effectively improve the flexural strength and toughness of UHPC. The hooked-end steel fibers commonly used by Qinglong enhance matrix bonding through mechanical anchoring, giving UHPC a flexural strength of 20-30MPa. However, steel fibers have a high density (7.8g/cm³), which increases the self-weight of components, and they may rust in chloride ion environments, which needs to be addressed through copper plating or stainless steel materials.

Non-metallic fibers are represented by PVA fibers, whose advantages are alkali corrosion resistance, low density (1.3g/cm³), and a moderate elastic modulus (40GPa). PVA fibers have high bonding strength with the cement matrix and can produce a significant bridging effect, making them particularly suitable for preparing high-toughness UHPC. In the red curtain wall project of the Wuhan Han Show Theatre, white PVA fibers were selected to precisely control color uniformity, avoiding the color difference problems that steel fibers might cause.

From the perspective of process adaptability, steel fibers have strong electrical conductivity and may interfere with thermal processes such as microwave curing; whereas non-metallic fibers have good insulation and broader process adaptability. In terms of cost, steel fibers have a low unit price but high density, so the cost per unit volume may be higher; PVA fibers have a high unit price but low density, so the comprehensive cost needs to be calculated based on the actual dosage. Qinglong recommends: steel fibers are preferred for general structural applications; PVA or basalt fibers can be chosen for decorative components with corrosion resistance or color requirements; and hybrid fiber systems can be adopted for special functional needs.