Standard Specification for
Steel Strand, Uncoated Seven-Wire
for Concrete Reinforcement
AASHTO Designation: M 203M/M 203-12
ASTM Designation: A416/A416M-10
American Association of State Highway and Transportation Officials
444 North Capitol Street N.W., Suite 249
Washington, D.C. 20001
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
Standard Specification for
Steel Strand, Uncoated Seven-Wire
for Concrete Reinforcement
AASHTO Designation: M 203M/M 203-12
ASTM Designation: A416/A416M-10
1. SCOPE
1.1. This specification covers two types and two grades of steel strand, uncoated seven-wire for use in
pretensioned and post-tensioned prestressed concrete construction. The two types of strand are
low-relaxation and stress-relieved (normal-relaxation). Low-relaxation strand shall be regarded as
the standard type. Stress-relieved (normal-relaxation) strand will not be furnished unless
specifically ordered or by arrangement between purchaser and supplier. Grade 1725 [250] and
Grade 1860 [270] have minimum ultimate strengths of 1725 MPa [250 ksi] and 1860 MPa
[270 ksi], respectively, based on the nominal area of the strand.
1.2. The values stated in either inch-pound units or SI units are to be regarded as standard. Within the
text, the inch-pound units are shown in brackets. The values stated in each system are not exact
equivalents; therefore, each system must be used independently of the other. Combining values
from the two systems may result in nonconformance with the specification.
1.3. The supplementary requirements in S1 shall be specified for 15.24-mm- [0.600-in.-] diameter
uncoated seven-wire steel strand if needed for applications in prestressed ground anchors.
2. REFERENCED DOCUMENTS
2.1. AASHTO Standard:
T 244, Mechanical Testing of Steel Products
2.2. ASTM Standards:
A981/A981M, Standard Test Method for Evaluating Bond Strength for 0.600-in.
[15.24-mm] Diameter Steel Prestressing Strand, Grade 270 [1860], Uncoated, Used in
Prestressed Ground Anchors
E328, Standard Test Methods for Stress Relaxation Tests for Materials and Structures
2.3. IEEE/ASTM Standard:
SI 10, American National Standard for Use of the International System of Units (SI):
The Modern Metric System
2.4. Military Standards:
MIL-STD-129, Marking for Shipment and Storage
MIL-STD-163, Steel Mill Products Preparation for Shipment and Storage
2.5. Federal Standard:
Fed. Std. No. 123, Marking for Shipments (Civil Agencies)
TS-4g M 203M/M 203-1 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
3. TERMINOLOGY
3.1. Description of Term Specific to This Standard:
3.1.1. strand—all strand shall be of the seven-wire type having a center wire enclosed tightly by
six helically placed outer wires with a uniform pitch of not less than 12 and not more than
16 times the nominal diameter of the strand.
3.1.1.1. Discussion—The direction of lay may be either right or left hand; however, strands of different
lays should not be spliced together.
4. ORDERING INFORMATION
4.1. Orders for seven-wire low-relaxation or stress-relieved (normal-relaxation) strand under this
specification should include the following information:
4.1.1. Quantity (meters) [feet],
4.1.2. Diameter of strand,
4.1.3. Grade of strand,
4.1.4. Type of strand,
4.1.5. Packaging,
4.1.6. AASHTO designation and year of issue, and
4.1.7. Special requirements, if any.
Note 1—A typical ordering description is as follows: 25 600 m [84,000 ft], 13 mm [0.5 in.],
Grade 1860 [270] low-relaxation strand, in 3600-m [12,000-ft] reelless packs conforming to
M 203M/M 203-____.
5. MATERIALS AND MANUFACTURE
5.1. Base Metal—The base metal shall be carbon steel of such quality that when drawn to wire,
fabricated into strand, and then thermally treated, it shall have the properties and characteristics
prescribed in this specification.
5.2. Wire—The wire from which the strand is to be fabricated shall be round and have a
dry-drawn finish.
Note 2—This product is a composite of seven wires and is produced to mechanical properties
only; the chemical composition of all wires or any individual wire is not pertinent to this
application, and heat identity is not necessarily maintained. It is possible that wire from more than
one heat may be used in the manufacture of a reel or pack. Traceability is based on pack identity
as maintained and reported by the manufacturer.
5.3. Treatment—After stranding, low-relaxation strand shall be subjected to a continuous thermal-
mechanical treatment to produce the prescribed mechanical properties. For stress-relieved
(normal-relaxation) strand, only thermal treatment is necessary. Temper colors that may result
from the thermal operation are considered normal for the finished appearance of this strand.
TS-4g M 203M/M 203-2 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
6. MECHANICAL PROPERTIES
6.1. Methods of testing for mechanical properties are described in Appendix A7 of T 244.
Low-relaxation strand shall also be tested as prescribed in ASTM E328.
6.2. Breaking Strength—The breaking strength of the finished strand shall conform to the requirements
prescribed in Table 1.
6.3. Yield Strength—Yield strength in kN [pounds] shall be measured at 1 percent extension under
load. The minimum yield strength shall be 90 percent for low-relaxation strand and 85 percent for
stress-relieved [normal-relaxation] strand of the breaking strength listed in Table 1. Initial loads
for the test and minimum yield strengths are listed in Table 2.
Table 1—Breaking Strength Requirements
Minimum
Breaking Nominal
Strand Nominal Diameter Strength Nominal Steel Mass of
Designation of Strand, of Strand, Area of Strand, Strand,
No. mm [in.] kN [lbf] mm2 [in.2] g/m [lb/1000 ft]
Grade 1725 [250]
6 6.4 [0.250] 40.0 [9,000] 23.2 [0.036] 182 [122]
8 7.9 [0.313] 64.5 [14,500] 37.4 [0.058] 294 [197]
9 9.5 [0.375] 89.0 [20,000] 1.6 [0.080] 405 [272]
11 11.1 [0.438] 120.1 [27,000] 69.7 [0.108] 548 [367]
13 12.7 [0.500] 160.1 [36,000] 92.9 [0.144] 730 [490]
15 15.2 [0.600] 240.2 [54,000] 139.4 [0.216] 1094 [737]
Grade 1860 [270]
9 9.53 [0.375] 102.3 [23,000] 54.8 [0.085] 432 [290]
11 11.11 [0.438] 137.9 [31,000] 74.2 [0.115] 582 [390]
13 12.70 [0.500] 183.7 [41,300] 98.7 [0.153] 775 [520]
13a 13.20 [0.520] 200.2 [45,000] 107.7 [0.167] 844 [568]
14 14.29 [0.563] 230.0 [51,700] 123.9 [0.192] 970 [651]
15 15.24 [0.600] 260.7 [58,600] 140.0 [0.217] 1102 [740]
16 15.75 [0.620] 277.4 [62,370] 149.2 [0.231] 1173 [788]
18 17.78 [0.700] 353.2 [79,400] 189.7 [0.294] 1487 [1000]
TS-4g M 203M/M 203-3 AASHTO
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Table 2—Yield Strength Requirements
Minimum Load at 1%
Strand Nominal Diameter Extension, kN [lbf]
Designation of Strand Initial Load, Low- Normal-
No. mm [in.] kN [lbf] Relaxation Relaxation
Grade 1725 [250]
6 6.4 [0.250] 4.0 [900] 36.0 [8,100] 34.0 [7,650]
8 7.9 [0.313] 6.5 [1,450] 58.1 [13,050] 54.7 [12,300]
9 9.5 [0.375] 8.9 [2,000] 80.1 [18,000] 75.6 [17,000]
11 11.1 [0.438] 12.0 [2,700] 108.1 [24,300] 102.3 [23,000]
13 12.7 [0.500] 16.0 [3,600] 144.1 [32,400] 136.2 [30,600]
15 15.2 [0.600] 24.0 [5,400] 216.2 [48,600] 204.2 [45,900]
Grade 1860 [270]
9 9.53 [0.375] 10.2 [2,300] 92.1 [20,700] 87.0 [19,550]
11 11.11 [0.438] 13.8 [3,100] 124.1 [27,900] 117.2 [26,350]
13 12.70 [0.500] 18.4 [4,130] 165.3 [37,170] 156.1 [35,100]
13a 13.20 [0.520] 20.0 [4,500] 180.1 [40,500] 170.1 [38,250]
14 14.29 [0.563] 23.0 [5,170] 207.0 [46,530] 195.5 [43,950]
15 15.24 [0.600] 26.1 [5,860] 234.6 [52,740] 221.5 [49,800]
16 15.75 [0.620] 27.7 [6,237] 249.7 [56,133] 235.9 [53,015]
18 17.78 [0.700] 35.3 [7,940] 318.0 [71,500] 300.2 [67,500]
6.3.1. The extension under load shall be measured by an extensometer calibrated with the smallest
division not larger than 0.0001 mm/mm [0.0001 in./in.] of gauge length.
6.4. Elongation—The total elongation under load shall not be less than 3.5 percent using a gauge
length of not less than 600 mm [24 in.]. It shall be permissible to determine the total elongation
value by adding to the 1.0 percent yield extension the percent extension or movement between the
jaws gripping the strand after yield determination. The percent is calculated on the new base
length of jaw-to-jaw distance.
6.5. Relaxation Properties—Low-relaxation strand shall have relaxation losses of not more than
2.5 percent when initially loaded to 70 percent of specified minimum breaking strength or not
more than 3.5 percent when loaded to 80 percent of specified minimum breaking strength of the
strand after 1000 h tested under the conditions listed in Sections 6.5.1 through 6.5.7.
6.5.1. If required, relaxation evidence shall be provided from the manufacturer’s records of tests on
similarly dimensioned strand of the same grade.
6.5.2. The temperature of the test specimen shall be maintained at 20 ± 2°C [68 ± 3.5°F].
6.5.3. The test specimen shall not be subjected to loading prior to the relaxation test.
6.5.4. The initial load shall be applied uniformly over a period of not less than 3 min and not more than
5 min, and the gauge length shall be maintained constant; load-relaxation readings shall
commence 1 min after application of the total load.
6.5.5. Overstressing of the test specimen during the loading operation shall not be permitted.
6.5.6. The duration of the test shall be 1000 h or a shorter period of at least 200 h, provided it can be
shown by records that an extrapolation of the shorter period test results to 1000 h will provide
similar relaxation values as the full 1000-h test.
TS-4g M 203M/M 203-4 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
6.5.7. The test gauge length should be at least 60 times the nominal diameter. If this gauge length
exceeds the capacity of the extensometer or testing machine, then it shall be permitted to substitute
a gauge length of 40 times the nominal strand diameter.
7. DIMENSIONS AND PERMISSIBLE VARIATIONS
7.1. The size of the finished strand shall be expressed as the nominal diameter of the strand in
millimeters [inches].
7.2. The diameter of the center wire of any strand shall be larger than the diameter of any outer wire in
accordance with Table 3.
Table 3—Diameter Relation between Center and Outer Wires
Minimum Difference
between
Strand Nominal Diameter Center Wire Diameter and
Designation of Strand Diameter of Any Outer Wire
No. mm in. mm in.
Grade 1725 [250]
6 6.4 0.250 0.025 0.001
8 7.9 0.313 0.038 0.0015
9 9.5 0.375 0.051 0.002
11 11.1 0.438 0.064 0.0025
13 12.7 0.500 0.076 0.003
15 15.2 0.600 0.102 0.004
Grade 1860 [270]
9 9.53 0.375 0.0508 0.002
11 11.11 0.438 0.0635 0.0025
13 12.70 0.500 0.0762 0.003
13a 13.20 0.520 0.0762 0.003
14 14.29 0.563 0.0889 0.0035
15 15.24 0.600 0.1016 0.004
16 15.75 0.620 0.1016 0.004
18 17.78 0.700 0.1143 0.0045
7.3. Permissible Variations in Diameter:
7.3.1. All Grade 1725 [250] strand shall conform to a size tolerance of ±0.40 mm [±0.016 in.] from the
nominal diameter measured across the crowns of the wires.
7.3.2. All Grade 1860 [270] strand shall conform to a size tolerance of +0.65 mm, –0.15 mm
[+0.026 in., –0.006 in.] from the nominal diameter measured across the crowns of the wire.
7.3.3. Variation in cross-sectional area and in unit stress resulting therefrom shall not be cause for
rejection provided the diameter differences of the individual wires and the diameters of the strand
are within the tolerances specified.
7.4. It shall be permitted to furnish, under this specification, specially dimensioned low-relaxation and
stress-relieved [normal-relaxation] strands with nominal diameters up to 19 mm [0.750 in.]. The
breaking strength shall be defined, and the yield strength, as defined in Section 6.3, shall not be
less than 90 percent and 85 percent of the specified minimum breaking strength for low-relaxation
and stress-relieved [normal-relaxation] strands, respectively. All other requirements shall apply.
TS-4g M 203M/M 203-5 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
8. WORKMANSHIP, FINISH, AND APPEARANCE
8.1. Joints:
8.1.1. There shall be no strand joints or strand splices in any length of the completed strand unless
specifically permitted by the purchaser.
8.1.2. During the process of manufacture of individual wires for stranding, welding shall be permitted
only prior to or at the time of the last thermal treatment, for example, patenting or control cooling.
There shall be no welds in the wire after it has been drawn through the first die in the wire drawing
except as provided in Section 8.1.3.
8.1.3. During fabrication of the strand, butt-welded joints are permitted in the individual wires, provided
there shall not be more than one such joint in any 45-m [150-ft] section of the completed strand.
8.1.4. When specifically ordered as “Weldless,” a product free of welds shall be furnished. When
“Weldless” is specified, the strand is produced as one continuous length with no welds as allowed
by Section 8.1.3.
8.2. The finished strand shall be uniform in diameter and shall be free of imperfections not consistent
with good commercial stranding practice.
8.3. When the strand is cut without seizings, the wire shall not fly out of position. If any wire flies out
of position and can be replaced by hand, the strand will be considered satisfactory.
8.4. The strand shall not be oiled or greased. Slight rusting, provided it is not sufficient to cause pits
visible to the unaided eye, shall not be cause for rejection.
Note 3—Guidance for evaluating the degree of rusting on prestressed concrete strand is presented
in Sason. 1
9. SAMPLING
9.1. Test specimens cut from either end of the strand package are permitted. Any specimen found to
contain a wire joint should be discarded and a new specimen obtained.
10. NUMBER OF TESTS
10.1. One specimen for test shall be taken from each 18-Mg [20-ton] production lot of finished strand,
and tested for breaking strength, yield strength, and elongation.
11. INSPECTION
11.1. If outside inspection is required, the manufacturer shall afford the inspector representing the
purchaser all reasonable facilities to satisfy that the material is being furnished in accordance with
this specification. All tests and inspections shall be made at the place of manufacture prior to
shipment, unless otherwise agreed upon at the time of purchase, and shall be so conducted as not
to interfere unnecessarily with the operation of the works.
Note 4—The purchaser should state, at the time of order, whether outside inspection is required
or waived.
TS-4g M 203M/M 203-6 AASHTO
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12. REJECTION
12.1. Failure of any test specimen to comply with the requirements of the specification shall constitute
grounds for rejection of the lot represented by the specimen.
12.2. The lot shall be resubmitted for inspection by testing a specimen from each reel or pack and
sorting out nonconforming material.
12.3. In case there is a reasonable doubt in the initial testing as to the ability of the strand to meet any
requirement of this specification, two additional tests shall be made on a specimen of strand from
the same reel or pack, and if failure occurs in either of these tests, the strand shall be rejected.
13. CERTIFICATION
13.1. If outside inspection is waived, a manufacturer’s certification that the material has been tested in
accordance with and meets the requirements of this specification shall be the basis of acceptance
of the material. The certification shall include the specification number, year-date of issue, and
revision letter, if any.
13.2. The manufacturer shall, when requested in the order, furnish a representative load-elongation
curve for each size and grade of strand shipped.
13.3. When the modulus of elasticity of a seven-wire strand is provided, the cross-sectional area used to
compute that modulus shall also be provided. The area provided in the certification shall be the
area used to calculate the modulus of elasticity.
13.4. A material test report, certificate of inspection, or similar document printed from or used in
electronic form from an electronic data interchange (EDI) transmission shall be regarded as having
the same validity as a counterpart printed in the certifier’s facility. The content of the EDI-
transmitted document must meet the requirements of the invoked AASHTO standard(s) and
conform to any existing EDI agreement between the purchaser and the supplier. Notwithstanding
the absence of a signature, the organization submitting the EDI transmission is responsible for the
content of the report.
Note 5—The industry definition as invoked here is: EDI is the computer-to-computer exchange
of business information in a standard format such as ANSI ASC X12.
14. PACKAGING AND MARKING
14.1. The strand shall be furnished on reels or in reelless packs having a minimum core diameter of
610 mm [24 in.] unless otherwise specified by the purchaser. Lengths on reels or in reelless packs
shall be as agreed upon at the time of purchase. The strand shall be well protected against
mechanical injury in shipping as agreed upon at the time of purchase. Each reel or reelless pack
shall have two strong tags securely fastened to it showing the length, size, types, grade,
M 203M/M 203 or ASTM A416, and the name or mark of the manufacturer. One tag shall be
positioned where it will not be inadvertently lost during transit, such as the core of a reelless pack.
The other tag shall be on the outside for easy identification.
14.2. For Government Procurement Only—When specified in the contract or order, and for direct
procurement by or direct shipment to the U.S. government, material shall be preserved, packaged,
and packed in accordance with the requirements of MIL-STD-163. The applicable levels shall be
specified in the contract. Marking for shipment of such material shall be in accordance with Fed.
Std. No. 123 for civil agencies and MIL-STD-129 for military agencies.
TS-4g M 203M/M 203-7 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
15. KEYWORDS
15.1. Prestressed concrete; seven-wire strand [tendon]; steel wire.
SUPPLEMENTARY REQUIREMENTS
Supplementary requirements shall apply only to 15.2-mm- [0.600-in.-] diameter strand. Grade 270
used in prestressed ground anchors or similar applications shall be specified at the time of
order placement. These requirements are not applicable to strand used in prestressed concrete
applications.
S1. BOND CAPACITY
S1.1. The results of bond-capacity tests performed in accordance with ASTM A981/A981M shall be
submitted to the purchaser. The strand specimens on which tests were performed shall be from
different lots and shall be representative for the strand ordered.
S1.2. The average pull force from six pull tests, performed in accordance with ASTM A981/A981M,
required to reach the 0.25-mm [0.01-in.] displacement described therein shall be at least 35.6 kN
[8000 lbf] with the individual minimum test value not less than 30.2 kN [6800 lbf]. For any future
retests, without changes in the manufacturing method and materials used, three tests shall be
considered adequate.
S1.3. Retests—If the test specimens fail to satisfy Section S1.2, six additional tests shall be performed,
and the results shall satisfy the acceptance criteria. Strand that failed the retest shall not be
considered acceptable for the use in prestressed ground anchors.
S1.4. Annual Test—The pull tests shall be performed annually as a minimum or repeated when, in the
opinion of the producer, a process change is made that is believed could decrease the bond
capacity of the strand.
1
Sason, A. S. “Evaluation of Degree of Rusting on Prestressed Concrete Strand,” PCI Journal 37, No. 3 (May/June
1992): 25–30. Reprints of this paper are available from the Precast/Prestressed Concrete Institute, 175 West Jackson
Blvd., Suite 1859, Chicago, Illinois 60604.
TS-4g M 203M/M 203-8 AASHTO
© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
