ISO 6934-2:1991

Overview

ISO 6934-2:1991 is an international standard developed by the International Organization for Standardization (ISO) that specifies the requirements for cold-drawn wire steel used in the prestressing of concrete. As Part 2 of the ISO 6934 series on steel for prestressing applications, this document focuses specifically on cold-drawn wire used for high tensile strength reinforcement in prestressed concrete structures.

This standard ensures the consistency, quality, and performance of cold-drawn wires to meet the rigorous demands of prestressed concrete applications. It aligns with the general specifications outlined in ISO 6934-1 and provides detailed parameters related to wire dimensions, mechanical properties, surface conditions, and delivery requirements.

Key Topics

• Material and Manufacturing
  The standard requires the cold-drawn wire to be produced from high carbon steel according to ISO 6934-1, ensuring material quality and consistency. The wire must be free from welds or joints to guarantee structural integrity.

• Surface Conditions
  The wire surface can be smooth, indented, ribbed, or twisted to optimize the bonding characteristics with concrete. Surface types are specified to improve adherence within prestressed concrete elements. Examples of these surface textures are provided in the annexes.

• Mechanical Properties
  Detailed specifications for tensile strength, yield limit, elongation, and fatigue resistance are included:

  • Tensile strength ranges typically from 1380 to 1960 N/mm² depending on wire diameter and class.
  • Minimum elongation under maximum load must meet criteria (e.g., 1.5% for raw wire, 3.5% for relaxed wire).
  • Fatigue resistance testing requires the wire to withstand 2 million cycles without failure under alternating stresses.
  • Relaxation limits are set to not exceed 10% after 1000 hours under specific load conditions.

• Dimensions and Tolerances
  Nominal diameters range from 3 mm up to 12.2 mm, with corresponding mass, tensile capacities, and bending radii stipulated. The wire must withstand mandatory bending and alternating bending tests to confirm ductility and performance.

• Delivery and Marking
  The wire should be supplied in coils or cut lengths, with coil diameters recommended to prevent damage and maintain material properties. Designation includes diameter, tensile strength class, surface type, and relaxation class.

Applications

ISO 6934-2:1991 cold-drawn wire steel is primarily used for:

• Prestressed Concrete Structures
  Utilized as reinforcement in beams, slabs, and other components where high tensile strength is required to withstand prestressing forces.

• Infrastructure Projects
  These wires are ideal for bridges, tunnels, railway sleepers, and retaining walls where durability and strong concrete bonding are critical.

• Precast Concrete Elements
  Applicable in precast units that demand uniform tensile properties and reliable stress transfer between steel and concrete.

• Specialized Construction
  The wire can be employed in applications such as sheet piling, tanks, and other concrete structures requiring prestress reinforcement.

Related Standards

ISO 6934-2 works in conjunction with several ISO standards including:

• ISO 6934-1:1991 - General specifications for steel used in prestressing concrete, covering fundamental material and mechanical quality requirements applicable to all wire types.
• ISO 6934-3, 4, 5 - Covering quenched and tempered wire, strands, and rolled steel bars respectively for prestressing applications.
• ISO 3768-1, ISO 3768-2 - These standards provide test methods relevant to stress relaxation and fatigue properties which complement the requirements for prestressing wires.
• ISO 9001 - For quality management systems ensuring production consistency and traceability of prestressing steel products.

By adhering to ISO 6934-2:1991, manufacturers and engineers ensure that cold-drawn prestressing wires meet strict international quality standards, providing high strength, durability, and reliability necessary for long-lasting prestressed concrete construction. This robust standard supports best practices in material selection, testing, and application, essential for optimal structural performance and safety.