🔩 Prestressing steel for concrete (bars, wires, strands) — tensile test with Agt and modulus of elasticity, bend test, reverse bend test of wire, relaxation, fatigue, stress corrosion, deflected tensile test, geometry and mass per metre, PN-EN ISO 15630-3

Construction PN-EN ISO 15630-3

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 15630-3:2025-12, in full: “This document specifies test methods applicable to prestressing steel (bar, wire or strand) for concrete. This document does not cover the sampling conditions that are dealt with in the product standards.” Of the 2025 edition we have only the beginning of the text: the iTeh preview of ISO 15630-3:2025 (fourth edition, 2025-06) from the cover to the end of the introduction (page vii) and the preview of SIST EN ISO 15630-3:2025 with the European foreword and clauses 1–3.1 (to page 1). The technical content is taken from three other documents, and each paragraph states which: the final draft ISO/FDIS 15630-3 of January 2025 with the changes against the 2019 edition marked (to the end of the manual determination of Agt in 5.3.1, page 6), the 2019 edition (third, corrected version — to the beginning of 6.3, page 6) and the 2010 edition (second — to 7.1, page 6). Titles of clauses whose text we do not have are our own renderings of the English table of contents.

ACCORDING TO THE 2025 EDITION (table of contents, forewords, introduction, clauses 1–3.1). The standard was prepared by ISO/TC 17 “Steel”, Subcommittee SC 16 “Steels for the reinforcement and prestressing of concrete”, in collaboration with CEN/TC 459/SC 4 (Vienna Agreement). The fourth edition replaces the third (ISO 15630-3:2019), which has been technically revised; as the main changes the foreword lists two new informative annexes: B — stress corrosion test in thiocyanate solution with galvanostatic current, and C — stress corrosion test in distilled water. CEN approved EN ISO 15630-3:2025 on 29 May 2025 without any modification of the ISO text; national standards bodies were to implement it, and to withdraw conflicting national standards, by December 2025 at the latest; it supersedes EN ISO 15630-3:2019. Introduction: the ISO 15630 series aims to provide all relevant test methods for reinforcing and prestressing steels in one place; this part covers standard test methods and specialized ones, not commonly used in routine testing, which should only be considered where relevant or specified in the product standard; the standard refers to International Standards on the testing of metals and adds complementary provisions; the options for agreement between the parties are listed in Annex A. Normative references (clause 2, ten standards): ISO 4957 (tool steels — added against 2019 in the FDIS), ISO 4965-1 and ISO 4965-2 (dynamic force calibration for uniaxial fatigue testing), ISO 6508-1 (Rockwell hardness), ISO 6892-1 (tensile testing at room temperature), ISO 7500-1 (testing machines), ISO 7801 (wire — reverse bend test), ISO 7802 (wire — wrapping test), ISO 9513 (extensometers), ISO 16020 (vocabulary — basis of clause 3.1). Table of contents: clause 4 — general provisions concerning test pieces, 5 — tensile test (5.3.2 — modulus of elasticity), 6 — bend test, 7 — reverse bend test, 8 — wrapping test, 9 — isothermal stress relaxation test (e.g. initial force, maintenance of strain, temperature, frequency of force and strain recording, duration), 10 — axial force fatigue test (e.g. stability of force and frequency, counting of cycles, validity of the test), 11 — stress corrosion test in a solution of thiocyanate (e.g. test cell with the solution, temperature, termination of the test, median lifetime to fracture), 12 — deflected tensile test (anchorages, mandrel, loading device), 13 — chemical analysis, 14 — measurement of the geometrical characteristics (ribs, indentations, lay length of strand P, straightness), 15 — relative rib area fR (with simplified formulae), 16 — deviation from nominal mass per metre, 17 — test report; Annexes A–C.

GENERAL PROVISIONS AND TENSILE TEST (clauses 4–5.3.1 — according to the 2025 FDIS, compared sentence by sentence with the 2019 text). Samples are taken from the finished product before packaging unless otherwise agreed or specified in the product standard; when sampling from the packaged product (coil, bundle), care is needed to avoid plastic deformation, which can change the properties. The free length of the test piece shall be sufficient to determine Agt; for manual A the test piece is marked according to ISO 6892-1, and for manual Agt of a bar or wire — with equidistant marks 20 mm, 10 mm or 5 mm apart, depending on the diameter. Testing machine verified and calibrated according to ISO 7500-1, at least class 1; extensometer of class 1 according to ISO 9513 for E, Fp0,1 and Fp0,2, a class 2 extensometer may be used for Agt; grips shall avoid breaks in or very near the grips. The test is performed according to ISO 6892-1, determining the modulus of elasticity E, the 0,1 % and 0,2 % proof forces (Fp0,1, Fp0,2), the maximum force Fm, the percentage total extension at maximum force Agt and/or the percentage elongation after fracture A, and the percentage reduction of area Z. E, Fp0,1, Fp0,2 and Agt are determined with an extensometer whose gauge length is given in the product standard; accurate values of Agt can only be obtained with an extensometer. If it cannot stay on until fracture or until the maximum force has been passed, loading continues until the extension is just greater than that corresponding to Fp0,2, the extensometer is removed and the cross-head distance noted, loading continues to fracture and the final distance is noted — the difference, as a percentage of the original cross-head distance, is added to the extensometer result. For wires and bars Agt may be determined manually after fracture with Formula (1): Agt = Ar + Rm/2000, where Ar is the percentage uniform elongation after fracture (only Ar is explained at this point of the standard); Ar is measured like A, on the longer fractured part, on a gauge length of 100 mm, as close as possible to the fracture but not closer than 50 mm or 2d (whichever is greater); the measurement may be considered invalid if the distance r1 between the grips and the gauge length is less than 20 mm or d (whichever is greater). A preliminary force, e.g. about 10 % of the expected maximum force, before placing the extensometer is preferable. If Agt is not completely determined with an extensometer, this is stated in the test report; for routine tests by prestressing steel producers the test information should be in internal documentation. In this range the FDIS changes only wording and formatting against 2019 — no number and no requirement; it adds ISO 4957 to the references and moves the sentence about Annex A from the scope to the introduction.

FURTHER ACCORDING TO THE 2019 EDITION (end of 5.3.1 — beginning of 6.3). Tensile properties (Fp0,1, Fp0,2, Fm) are recorded in force units. The elongation A is determined on an original gauge length of eight nominal diameters (8d) unless the product standard specifies otherwise; in case of dispute A is determined manually. A fracture within 3 mm of the grips makes the test in principle invalid and permits a retest — the results may nevertheless be taken into account if all values meet the specified values. The modulus of elasticity (5.3.2) is the slope of the linear portion of the force–extension diagram divided by the nominal cross-sectional area of the test piece Sn; for cold-drawn products (e.g. strands and plain wires) the slope can be determined between 0,2Fm and 0,7Fm (Formula 2) — by linear regression of the stored data or by a best-fit visual technique; in special cases, e.g. hot-rolled and stretched bars, where this is not possible, a secant modulus between 0,05Fm and 0,7Fm is determined (Formula 3); within the force range over which the modulus is determined the stress rate must not be changed. Bend test (clause 6): a device with mandrel, support and carrier (Figure 2 — either the mandrel with the support or the carrier may rotate) or supports and a mandrel (e.g. according to ISO 7438); temperature from 10 °C to 35 °C; the test piece is bent over a mandrel, and the angle of bend and the mandrel diameter are given by the product standard.

INTERPRETATION OF THE BEND TEST — ONLY ACCORDING TO THE 2010 EDITION (6.4). Interpretation follows the requirements of the product standard; if there are none, the absence of cracks visible to a person with normal or corrected vision is evidence that the test piece withstood the bend test; a superficial ductile tear at the base of the ribs or indentations is not a failure — it is considered superficial when its depth is not greater than its width. The 2019 and 2025 editions have a subclause 6.4 with the same title (tables of contents), but we do not have its text from those editions.

STATUS (catalogue cards as of 30.09.2026). The card of PN-EN ISO 15630-3:2025-12 (English version) has no “Withdrawn” heading — this edition is CURRENT: published 04-12-2025, 56 pages, price group U, Metallurgy Sector, technical committee KT 123 for testing the properties of metals, ICS 77.140.15, “Introduces: EN ISO 15630-3:2025 [IDT], ISO 15630-3:2025 [IDT]”, “Replaces: PN-EN ISO 15630-3:2019-04 - English version, PN-EN ISO 15630-3:2019-04 - Polish version”; no additional elements. There is no Polish version of the 2025 edition in the catalogue: the PKN search for “PN-EN ISO 15630-3” (30.09.2026) shows the editions 2002 (English), 2004 (Polish), 2011 and 2019-04 (both in two versions) and 2025-12 (English only). The cards of PN-EN ISO 15630-3:2019-04 in both versions: “Withdrawn and replaced by PN-EN ISO 15630-3:2025-12 - English version”, withdrawal date 04-12-2025 (English version — published 19-04-2019, 42 pages; Polish — 03-08-2020, 38 pages; both without additional elements). Card of PN-EN ISO 15630-3:2011 (Polish version): withdrawn 19-04-2019, replaced by PN-EN ISO 15630-3:2019-04. What the change from 2019 to 2025 means for the result: in clauses 4–5.3.1 (comparison with the FDIS) — no number and no requirement, clause 2 gained ISO 4957; as technical changes the ISO foreword lists only the new informative Annexes B and C (two additional variants of the stress corrosion test); the further clauses of the two editions were not compared. The status of ISO 15630-3:2025 on the ISO website was not checked.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 30.09.2026). The number 15630-3 appears in 26 records of 9 laboratories (all notations of the number, including one “PN-EN-ISO 15630-3” — AB 023). Current scopes on the PCA website (read 30.09.2026, scope issues from 16.07.2025 to 22.09.2026): 35 notations of the number in 29 items — AB 1413 gives the 2011 and 2019-04 editions in each of its two items, AB 1869 gives 2019-04 and 2025-12 in each of its four, and at AB 024 the geometry measurements have four rows with the number in PCA, which the copy merges into one record. Editions in PCA: 2011 — AB 005 and AB 1413; 2019 or 2019-04 — AB 024, AB 372, AB 1251, AB 1413, AB 1562, AB 1869; 2025-12 — AB 193 (in scope issue No. 26 of 22.09.2026, in all five items; the database copy, data up to 17.09.2026, still has 2019-04 there) and AB 1869; undated — AB 023. None of these items is suspended. The “Laboratories” tab searches for notations BEGINNING WITH “PN-EN ISO 15630-3” and shows all 9 laboratories — checked with the tab query on the production server labcoda.pl on 30.09.2026: 9 (under “PN-EN-ISO 15630-3” — 1, the same AB 023; under “EN ISO 15630-3” — 0).

QUANTITY AND TEST OBJECT (items in PCA). Tensile test — all 9 laboratories (AB 005 separately lists breaking force, elongation and the modulus of elasticity “calculated”); upper force limit from 250 kN (AB 193 in one of its two items, AB 1869) to 5000 kN (AB 005, range (0–5000) kN). Bend test — AB 193, AB 1413, AB 1869. Clause 7 (reverse bend) — AB 024 (“przeginanie dwukierunkowe drutu”, wire with a diameter below 6,0 mm, together with PN-ISO 7801:1996), AB 193 and AB 1869 (in an item named “odginanie”, i.e. rebend). Geometry, relative rib area and mass per metre — AB 023, AB 024, AB 193, AB 1869. Only AB 023: relaxation (up to 200 kN, diameters up to 18 mm), resistance to stress corrosion (“solution A method” and “solution B method”, up to 200 kN, diameters up to 18 mm) and “Próba rozciągania z odginaniem” ((50–1000) kN, diameters up to 18 mm) — the latter corresponds to clause 12 (deflected tensile test). Only AB 372: fatigue test (force up to ±1000 kN, displacement up to ±200 mm). Test object: prestressing steel (AB 005, AB 1413, AB 1562), strands and wires for prestressed structures (AB 023), joint items for reinforcing and prestressing steel, sometimes also welded fabric (AB 024, AB 193, AB 372, AB 1869), steel bars, wires and strands (AB 1251); at AB 023 the item for geometry and relative rib area has the object “Stal zbrojeniowa” (reinforcing steel), and the static tensile test — “Stal, stopy metali, elementy stalowe” (steel, metal alloys, steel components).

NEXT TO THIS STANDARD (the same records of the database copy, all notations of the numbers; checked against PCA). PN-EN ISO 6892-1 — 7 laboratories (AB 023, AB 024, AB 193, AB 1251, AB 1413, AB 1562, AB 1869), six of them with the method letter B (AB 193 in one of its two items; at AB 023 the addition “metoda B” is in PCA, but the copy loses it); PN-EN ISO 15630-1 — 6 (AB 023, AB 024, AB 193, AB 372, AB 1251, AB 1869); PN-EN ISO 15630-2 — 5 (AB 023, AB 024, AB 193, AB 372, AB 1869); PN-H-93220:2018-02 — AB 372 and AB 1251 (at AB 1251 written “PN-H 93220”); PN-ISO 6935-2:1998 with amendment Ak — AB 193; PN-EN ISO 7438 (editions 2006 and 2021-04) — AB 1413; PN-ISO 7801:1996 — AB 024; in-house procedures — AB 024 (Instrukcja Badań QLiB-0301) and AB 193 (Procedura badawcza 07.06.00). Only AB 005 (three items) and AB 023 (stress corrosion, relaxation, deflected tensile test) cite the standard without any other document. The tensile test of metals according to PN-EN ISO 6892-1, the bend test according to PN-EN ISO 7438 and parts 1 (reinforcing bars, rods and wire) and 2 (welded fabric and lattice girders) of this series have separate entries in the Knowledge Base.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Sampling: a length taken from a coil or bundle with plastic deformation has different properties from the product — the standard calls for special care to avoid this; sampling conditions are in the product standard, not in this one. Measurement: a class 2 extensometer is sufficient only for Agt — used for E, Fp0,1 or Fp0,2 it gives a number that looks correct but does not conform to the standard; Agt from the manual method (bars and wires only) or from adding the cross-head displacement is not an extensometer measurement — this must be stated in the test report; a gauge length for Ar closer than 50 mm (or 2d) to the fracture or closer than 20 mm (or d) to the grips gives a measurement that may be considered invalid; after a fracture within 3 mm of the grips the result may be taken into account only if all values meet the requirements; A on an original gauge length other than 8d without a basis in the product standard is not comparable. Calculation: in the modulus of elasticity Fm and the extensions are measurements of the same test (extensometer), while Sn is a nominal value, not a measurement; a force range other than the one provided for the given product (0,2Fm–0,7Fm or the secant 0,05Fm–0,7Fm) or a change of the loading rate within that range gives a different value of E. In the formula for manual Agt, Ar is a measurement on the fractured test piece and Rm is a result of the same tensile test (tensile testing standard — PN-EN ISO 6892-1, separate entry). According to the standard (2019 edition) tensile properties (Fp0,1, Fp0,2, Fm) are recorded in force units, while six of the nine scopes list stresses Re, Rp and Rm next to this number (AB 1413 also the maximum force Fm; AB 005 — the breaking force) — these are different quantities, not different units of the same quantity. In the scopes: AB 024 gives clauses 13, 14, 15 (and 13, 15) with the 2019 edition — this is the numbering of the 2010 edition (geometry, fR, mass per metre); in the 2019 and 2025 editions clause 13 is chemical analysis, and geometry, fR and mass per metre are clauses 14, 15, 16 (as AB 193 gives them). At AB 193 and AB 1869 clause 7 of this part stands in an item called “odginanie” (rebend) together with clause 7 of part 1 — in part 3 clause 7 is the reverse bend test of wire according to ISO 7801, not a rebend test.

WHAT WE DO NOT GIVE. We do not have the text of the 2025 edition from clause 4 on: clauses 4–5.3.1 are read from the FDIS, the following ones from the 2019 edition (to the beginning of 6.3) and the 2010 edition (6.4). We do not give the procedure or conditions of the reverse bend, wrapping, relaxation, fatigue, stress corrosion (including the composition of solutions A and B mentioned in the scope of AB 023, and the content of the new Annexes B and C), deflected tensile tests, the chemical analysis, the measurements of geometry, fR and mass per metre, the options of Annex A or the requirements for the test report; we do not know where the standard refers to ISO 4957 and ISO 6508-1. We did not check whether the standard is referred to in legislation.

Method principle

Prestressing steel for concrete (bars, wires, strands) is tested with methods collected in one standard: the tensile test according to ISO 6892-1 with complementary provisions (extensometer for E, Fp0,1, Fp0,2 and Agt, tensile properties recorded in force units, modulus of elasticity from the slope of the force–extension diagram on the nominal cross-sectional area), technological tests (bend test, reverse bend test of wire according to ISO 7801, wrapping test according to ISO 7802) and specialized methods used when relevant or required in the product standard — the table of contents lists isothermal stress relaxation, axial force fatigue, stress corrosion in a thiocyanate solution and the deflected tensile test, as well as chemical analysis, measurement of geometrical characteristics, relative rib area and deviation of mass per metre.

Applications

• Prestressing steel for concrete — bars, wires and strands: tensile test (Fm, Fp0,1, Fp0,2, Agt, A, Z, modulus of elasticity) in the scopes of 9 laboratories, in seven of them together with PN-EN ISO 6892-1
• Joint items for reinforcing and prestressing steel — together with parts 1 and 2 of this series (bars, rods and wire; welded fabric and lattice girders)
• Specialized tests required in the product standard: isothermal relaxation, stress corrosion and deflected tensile test (in the scopes — AB 023), fatigue test (AB 372)

Key parameters

Standard

Standard number

PN-EN ISO 15630-3:2025-12 (wersja angielska; EN ISO 15630-3:2025, ISO 15630-3:2025 IDT)

Title (PL)

Stal do zbrojenia i sprężania betonu — Metody badań — Część 3: Stal do sprężania

Title (EN)

Steel for the reinforcement and prestressing of concrete — Test methods — Part 3: Prestressing steel

Step-by-step procedure

1. Sampling

   From the finished product before packaging unless otherwise agreed or specified in the product standard; when sampling from a coil or bundle avoid plastic deformation; sampling conditions — in the product standard. PN-EN ISO 15630-3:2025-12 current (card as of 30.09.2026).

2. Preparing the tensile test piece

   Free length sufficient to determine Agt; marking according to ISO 6892-1 for manual A, and for manual Agt of a bar or wire — marks every 20 mm, 10 mm or 5 mm depending on the diameter.

3. Tensile test

   According to ISO 6892-1: E, Fp0,1, Fp0,2, Fm, Agt and/or A and Z; extensometer for E, Fp0,1, Fp0,2 and Agt, preferably after a preliminary force of about 10 % of the expected Fm; if it has to be removed — beyond the extension at Fp0,2 the further increase is taken from the cross-head distance and added as a percentage.

4. Calculations

   Manual Agt (bars, wires): Agt = Ar + Rm/2000, Ar on a gauge length of 100 mm; A on an original gauge length of 8d (2019 edition); E from the slope between 0,2Fm and 0,7Fm or the secant 0,05Fm–0,7Fm, on the nominal cross-sectional area Sn (5.3.2, 2019 edition); Fp0,1, Fp0,2 and Fm in force units.

5. Bend test

   From 10 °C to 35 °C, over a mandrel; angle and mandrel diameter according to the product standard (2019 edition). Interpretation according to the product standard, and without its requirements — no cracks visible to a person with normal or corrected vision; a superficial ductile tear at the base of the ribs (depth not greater than width) is not a failure (6.4 according to the 2010 edition).

6. Specialized tests and report

   Reverse bend test of wire (ISO 7801), wrapping (ISO 7802), relaxation, fatigue, stress corrosion, deflected tensile test, chemical analysis, geometry, fR and mass per metre — the procedure is NOT GIVEN. If Agt was not completely determined with an extensometer, this is stated in the test report.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Fracture of a wire, bar or strand under a high force (in the scopes up to 5000 kN) — machine guards and a safety zone during the tensile test; the text of the standard we have read contains no health and safety warnings
• SUBSTANTIVE NOTE: the way Agt is determined (extensometer, adding the cross-head displacement, manual method) changes the result — this information must be in the test report; clause numbers in the 2019 and 2025 editions differ from the 2010 edition from clause 8 onwards

Frequently asked questions