Coiled (cold-drawn) fibers and melt-extracted fibers are standardized under ASTM A820/A820M and ISO 22034, specifying types, dimensions, tensile strength, and testing procedures for use in fiber-reinforced concrete.

Coiled (Cold-Drawn) Fiber Standards

Coiled fibers, also known as cold-drawn wire fibers, are produced by drawing steel wire to the desired diameter and optionally deforming it for better anchorage in concrete. Key standards include:

• ASTM A820/A820M defines Type I as cold-drawn wire fibers, which may be straight or deformed for improved bonding in concrete .
• ISO 22034 specifies that fibers must withstand bending around a 3 mm diameter pin to 90° at temperatures not less than 16°C without breaking .
• Tensile strength: Individual fibers must meet a tolerance of ±15% for Rm, with at least 95% of specimens conforming to the specified value .
• Testing: Fibers are clamped in testing machines with a minimum length of 20 mm to measure tensile properties .
• Applications: Used in sprayed concrete, flooring, precast, in-situ, and repair concretes .

Melt Fiber Standards

Melt-extracted fibers are produced by melting steel and drawing it into fibers, resulting in Type III fibers under ASTM A820/A820M . Key points include:

• Physical properties: Melt fibers are tested for minimum length, tensile strength, and deformation resistance similar to cold-drawn fibers .
• Shape and anchorage: They may be straight or deformed to improve bonding in concrete .
• Testing: Fibers are clamped and tested for tensile strength and bending resistance, ensuring they meet ASTM and ISO requirements .
• Applications: Suitable for fiber-reinforced concrete where uniform dispersion and high strength are required .

General Requirements

• Dimension and tolerance: Both fiber types have specified diameters, lengths, and tolerances to ensure consistent performance .
• Container labeling: Each shipping container must indicate fiber type, material, size, specification designation, net weight, and manufacturer .
• Volume fraction in concrete: The amount of fiber added is based on the volume fraction (Vf) to achieve the desired mechanical properties . In summary, coiled (cold-drawn) fibers and melt-extracted fibers are rigorously standardized to ensure consistent mechanical performance, proper anchorage in concrete, and safe handling, with ASTM A820/A820M and ISO 22034 providing the primary specifications for testing, dimensions, and physical properties.