Overview
ISO 6934-1:1991 - "Steel for the prestressing of concrete - Part 1: General requirements" establishes the general requirements, definitions and delivery/testing rules for high‑tensile steel used in prestressed concrete. It is the umbrella part of the ISO 6934 series and works with Parts 2–5, which specify properties for cold‑drawn wire, quenched & tempered wire, strand and hot‑rolled bars. ISO 6934-1 covers material types, manufacturing limits, surface condition, identification, testing scope and information to be supplied by the purchaser.
Key topics and technical requirements
- Scope and product types: Defines prestressing steel forms - cold‑drawn wire, quenched & tempered wire, strand (including 2, 3, 7 and 19‑wire configurations) and hot‑rolled bars.
- Manufacturing: Allows any process except air or mixed air/oxygen bottom‑blown steelmaking.
- Chemical composition: Related to product type, size and tensile strength; cast analysis may be supplied on request. Sulfur and phosphorus in cast analysis shall not exceed 0.04%.
- Geometrical properties: Based on nominal diameters or nominal cross‑sectional area with tolerances; coil diameters should permit uncoiling without affecting properties.
- Mechanical properties & acceptance:
- Tensile properties - maximum force, proof force (0.1% non‑proportional elongation is mandatory; 0.2% may be specified), and percentage total elongation at maximum force are specified as characteristic values (at least 95% of population expected to meet them).
- Bending/ductility - verified by bend or reverse‑bend tests per relevant ISO parts.
- Long‑term behaviour - isothermal relaxation measured at 20°C for 1000 h (values at 60%, 70%, 80% of nominal tensile strength; 60% and 80% provided if requested). Fatigue behaviour can be demonstrated on request (Annex A refers to fatigue testing such as 2×10^6 cycles at defined stress ranges).
- Surface condition: Steel must be free from defects that impair performance; slight rust acceptable if not pitting. Additional coatings only by agreement.
- Testing & delivery: Defines inspection, labeling, coil size, storage/transport protection and the information purchasers must supply.
Applications and practical value
- Used to specify and procure prestressing steel for prestressed concrete structures: bridges, buildings, precast elements, post‑tensioning systems.
- Helps manufacturers, testing laboratories and quality inspectors implement consistent testing, certification and acceptance criteria for wire, strand and bars.
- Supports designers and contractors in selecting steels with known tensile, relaxation and fatigue performance for durable prestressed components.
- Steel manufacturers and suppliers, structural and prestressing engineers, procurement officers, testing laboratories, and certification bodies involved in prestressed concrete projects.
Related standards
