ASTM A421/A421M-21

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of the standard as published by ASTM is to be considered the official document.
Designation: A421/A421M − 15 A421/A421M − 21 American Association State
Highway and Transportation Officials Standard
AASHTO No.: M 204
Standard Specification for
Stress-Relieved Steel Wire for Prestressed Concrete
This standard is issued under the fixed designation A421/A421M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This specification covers two types of stress-relieved round high-carbon steel wire commonly used in prestressed concrete
construction, as follows:
1.1.1 Type BA wire is used for applications in which cold-end deformation is used for anchoring purposes (Button Anchorage),
and
1.1.2 Type WA wire is used for application in which the ends are anchored by wedges, and no cold-end deformation of the wire
is involved (Wedge Anchorage).
1.2 A supplementary requirement (S1) is provided for use where low-relaxation wire and relaxation testing for that product is
required by the purchaser. The supplementary requirement applies only when specified in the purchase order.order or contract.
1.3 This specification is applicable for orders in either inch-pounds units (as Specification A421) or in SI units (as Specification
A421M).
1.4 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units are
shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used
independently of the other. Combining values from the two systems may result in non-conformance with the specification.
1.5 The text of this specification references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables) shall not be considered as requirements of the specification.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This specification is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.05
on Steel Reinforcement.
Current edition approved Nov. 1, 2015May 1, 2021. Published November 2015May 2021. Originally approved in 1958. Last previous edition approved in 20102015 as
A421/A421M – 10.A421/A421M – 15. DOI: 10.1520/A0421_A0421M-15.10.1520/A0421_A0421M-21.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A421/A421M − 21
2. Referenced Documents
2.1 ASTM Standards:
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A751 Test Methods and Practices for Chemical Analysis of Steel Products
E328 Test Methods for Stress Relaxation for Materials and Structures
2.2 Military Standard:
MIL-STD-129 Marking for Shipment and Storage
2.3 Federal Standard:
Fed. Std. No. 123 Marking for Shipments (Civil Agencies)
3. Ordering Information
3.1 Orders for stress-relieved steel wire under this specification shall contain the following information:
3.1.1 Quantity (feet [metres]),
3.1.2 Nominal diameter (inches [millimetres]),
3.1.3 Type BA or WA wire, and
3.1.4 ASTM designation A421 [A421M] and year of issue.
3.2 It The purchaser shall be the responsibility of the purchaser to specify all requirements that are necessary for material ordered
to this specification. Such requirements shall include, but are have the option to specify additional requirements, including but not
limited to, the following:
3.1.1 Quantity lb [kg],
3.1.2 Nominal diameter,
3.2.1 Name of material (uncoated stress-relieved Sampling—number of test specimens (9.1steel wire for prestressed concrete,
Type BA or WA wire),),
3.2.2 If outside inspection is required Requirements for inspection (10.1),
3.2.3 Packaging, Package marking (13.2),
3.2.4 Supplementary Requirement S1 (if desired), Relaxation evidence on similarly dimensioned wire of the same grade (S1.5.1),
and
3.2.5 ASTM designation and date of issue.Other special requirements, if any.
4. Manufacture
4.1 Process—The steel shall be made by any commercially accepted process.
4.2 Internal Soundness—A sufficient discard shall be made to ensure freedom from injurious piping and undue segregation.
4.3 Wire—The wire shall be cold-drawn to size and suitably stress-relieved after cold drawing by a continuous heat treatment to
produce the prescribed mechanical properties.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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A421/A421M − 21
5. Mechanical Property Requirements
5.1 Tensile Strength—The tensile strength of Type BA wire and Type WA wire shall conform to the requirements prescribed in
Table 1, and shall be determined as prescribed in Test Methods and Definitions A370, including Annex A4.
5.2 Yield Strength:
5.2.1 The minimum yield strength for all wire, measured by the 1.0 % extension under load method, shall not be less than 85 %
of the specified minimum tensile strength.
5.2.2 The extension under load shall be measured by an extensometer calibrated with the smallest division not larger than 0.0001
in./in. [0.0001 mm/mm] of gagegauge length.
5.2.3 The initial load corresponding to the initial stress prescribed in Table 2 shall be applied to the test specimen, at which time
the extensometer is attached and adjusted to a reading of 0.001 in./in. [0.001 mm/mm] of gagegauge length. The load shall then
be increased until the extensometer indicates an extension of 1 %. The load for this extension shall be recorded. The stress
corresponding to this load shall meet the requirements for stress at 1 % extension prescribed in Table 2.
5.3 Elongation—The total elongation under load of all wire shall not be less than 4.0 % when measured in a gagegauge length
of 10 in. [250 mm]. The elongation shall be determined by an extensometer which is placed on the test specimen after a load
corresponding to the initial stress prescribed in Table 2 is applied. If the fracture takes place outside of the gagegauge length and
the elongation so measured meets the minimum requirements, no further testing shall be required. If the elongation is less than
the minimum requirements, the test shall be considered an invalid test and a retest made.
6. Diameter and Permissible Variations
6.1 Wire meeting the requirements of this specification is normally ordered in the nominal diameters shown in Table 1.
6.2 The diameter of the wire shall not vary from the nominal diameter specified by more than 60.002 in. [60.05 mm].
6.3 The wire shall not be out-of-round by more than 0.002 in. [0.05 mm].
7. Workmanship and Finish
7.1 Cast—A wire sample test specimen having a chord length of 60 in. [1500 mm] shall have an offset at the center of the chord
of not more than 3 in. [75 mm]. This is equivalent to a chord of an arc of a circle not less than 25 ft [7.6 m] in diameter.
7.2 Type BA Wire—Type BA wire shall be of suitable quality to permit cold forming of button heads for anchorage. Splitting shall
not be considered a cause for rejection if the button anchorage is capable of developing the specified minimum required tensile
strength of the wire.
7.3 The wire shall be free of kinks.
7.4 The wire shall be furnished in firmly tied coils having a minimum inside diameter of 48 in. [1200 mm]. Each coil shall be
of one continuous length.
TABLE 1 Tensile Strength Requirements
Nominal Tensile Strength, min, psi [MPa]
Diameter,
Type BA Type WA
in. [mm]
A
0.192 [4.88] 250 000 [1725]
0.196 [4.98] 240 000 [1655] 250 000 [1725]
0.250 [6.35] 240 000 [1655] 240 000 [1655]
0.276 [7.01] 235 000 [1620] 235 000 [1620]
A
This size is not commonly furnished in Type BA wire.
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TABLE 2
...