ISO 15630-3:2025

Overview

ISO 15630-3:2025 - “Steel for the reinforcement and prestressing of concrete - Test methods - Part 3: Prestressing steel” (Fourth edition, 2025) specifies standardized test methods for prestressing steel in the form of bars, wire or strands used with concrete. The standard defines how to prepare test pieces, what equipment to use, and how to carry out and interpret a range of mechanical, durability and geometric tests. It does not cover sampling conditions, which are handled in product standards.

Key topics and requirements

ISO 15630-3:2025 focuses on practical, laboratory-level test procedures and includes, among others:

• Tensile tests (including determination of modulus of elasticity) - test pieces, equipment and procedures.
• Bend, reverse-bend and wrapping tests - procedures and interpretation for ductility and surface behavior.
• Isothermal stress relaxation test - principle, test-piece provisions, frame, force and length measurement, anchorage, load application and recording requirements.
• Axial force fatigue test - fatigue test principle, equipment and validity criteria.
• Stress-corrosion testing (thiocyanate solution) - cell and solution requirements, force maintenance and lifetime determination.
• Deflected tensile test - test arrangement, anchorages, mandrel and procedure for stranded elements.
• Chemical analysis and measurement of geometrical characteristics - rib and indentation measurements, strand lay length and other dimensional checks.
• General provisions covering sample preparation, test-piece dimensions and data recording frequency and duration for time-dependent tests.

The standard provides detailed instructions on test-piece preparation, instrumentation (force transducers, extensometers), environmental conditions (temperature control), and how to record and interpret results.

Applications and practical value

• Quality control in manufacturing of prestressing steel (bars, wires, strands).
• Performance verification for designers and contractors assessing relaxation, fatigue and corrosion susceptibility of prestressing components.
• Product development and R&D when evaluating new alloying, surface treatments or strand constructions.
• Third‑party testing and certification laboratories using consistent, internationally recognized procedures.
• Specification and compliance in procurement and structural specifications for prestressed concrete elements.

Using ISO 15630-3:2025 ensures reproducible, comparable test results that underpin safe design and long-term performance of prestressed concrete structures.

Related standards

• Other parts of the ISO 15630 series address test methods for reinforcing steel and complementary topics.
• Product standards and national regulations cover sampling procedures and acceptance criteria; ISO 15630-3 deliberately excludes sampling details.