ISO 6935-2:2019

Steel for the reinforcement of concrete - Part 2: Ribbed bars

This document specifies technical requirements for ribbed bars to be used as reinforcement in concrete. It is applicable to steel delivered in the form of bars, coils and de-coiled products. This document covers both weldable and non-weldable steels. It does not apply to ribbed bars produced from finished products, such as plates and railway rails. The production process is at the discretion of the manufacturer.

Aciers pour l'armature du béton — Partie 2: Barres à verrous

General Information

• Status: Published
• Publication Date: 02-Oct-2019
• ICS: 77.140.15 - Steels for reinforcement of concrete
• ICS: 91.080.40 - Concrete structures
• Technical Committee: ISO/TC 17/SC 16 - Steels for the reinforcement and prestressing of concrete
• Drafting Committee: ISO/TC 17/SC 16 - Steels for the reinforcement and prestressing of concrete
• Current Stage: 9060 - Close of review
• Completion Date: 04-Jun-2030

Relations

• Revises: ISO 6935-2:2015 - Steel for the reinforcement of concrete - Part 2: Ribbed bars
• Effective Date: 10-Dec-2016

Overview

ISO 6935-2:2019 - Steel for the reinforcement of concrete - Part 2: Ribbed bars specifies technical requirements for ribbed reinforcing bars (rebar) used in concrete. It applies to steel supplied as bars, coils and de‑coiled products, and covers both weldable and non‑weldable steels. The standard excludes ribbed bars made from finished products (for example plates or railway rails) and leaves production processes to the manufacturer’s discretion. The 2019 edition also introduces provisions for hot‑rolled threaded reinforcing bars.

Key topics and technical requirements

ISO 6935-2:2019 provides comprehensive criteria to ensure consistent quality and performance of rebar used in concrete structures. Major subjects include:

• Dimensions, mass per unit length and permissible deviations - nominal diameters, cross‑sectional areas and mass tolerances are defined (see the standard’s tables).
• Rib geometry and requirements - number and distribution of transverse ribs, rib height, spacing, flank inclination and relative rib area to ensure bond with concrete.
• Chemical composition - cast and product analysis requirements to control alloying elements and trace chemistry affecting weldability and mechanical behaviour.
• Mechanical properties - tensile properties (strength, yield, elongation), bending and rebending after ageing, and fatigue performance.
• Testing methods - procedures for tensile tests, bend/rebend tests, fatigue tests and chemical analysis, referencing ISO 15630‑1 and other normative documents.
• Designation, marking and identification - bar marking, bundle identification and examples of marking systems to support traceability.
• Conformity and acceptance - factory production control, evaluation of characteristic values, sampling and acceptance testing for deliveries.
• Annexes - informative examples of marking systems and options for agreements between manufacturer and purchaser.

Practical applications and who uses this standard

ISO 6935-2:2019 is essential for stakeholders who specify, produce, test or use steel reinforcement:

• Steel producers and rebar manufacturers - to design and certify ribbed bar products that meet international acceptance criteria.
• Structural and civil engineers - to select suitable reinforcement with known mechanical and bond characteristics for concrete design.
• Construction contractors and fabricators - for procurement, quality control and on‑site verification of rebar deliveries.
• Testing laboratories and inspection bodies - to perform standardized tensile, bend, fatigue and chemical tests.
• Regulators and procurement teams - to define contract specifications and ensure conformity assessment for safety and interchangeability.

Adopting ISO 6935-2 helps ensure reliable concrete reinforcement, improved rebar bond performance, and consistent material traceability across international projects.

Related standards

• ISO 15630‑1 (test methods for reinforcing bars, rods and wire)
• ISO 14284 (sampling and preparation for chemical analysis)
• ISO/TR 9769 (methods of analysis for steel and iron)
• Other parts of the ISO 6935 series for plain and other reinforcing steel types

Keywords: ISO 6935-2:2019, ribbed bars, rebar, reinforcement steel, concrete reinforcement, mechanical properties, chemical composition, testing, marking, conformity.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6935-2
Fourth edition
2019-10
Steel for the reinforcement of
concrete —
Part 2:
Ribbed bars
Aciers pour l'armature du béton —
Partie 2: Barres à verrous
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 Dimensions, mass per unit length and permissible deviations. 4
6 Requirements for ribs . 5
7 Chemical composition . 8
8 Mechanical properties .10
8.1 Tensile properties .10
8.2 Bending properties .12
8.3 Rebending properties after ageing .12
8.4 Fatigue properties .12
9 Testing .13
9.1 Tensile test .13
9.2 Conditions of testing .13
9.3 Bend test .13
9.4 Rebend test .13
9.5 Fatigue test .14
9.6 Chemical composition .14
10 Designation .14
11 Marking .14
11.1 Marking on bars .14
11.2 Identification of bundles.15
12 Evaluation of conformity .15
12.1 General .15
12.2 Evaluation of conformity during production .15
12.3 Acceptance testing of a specific delivery .16
12.3.1 General.16
12.3.2 Evaluation of characteristic values .16
12.3.3 Evaluation of specified minimum/maximum values .18
12.3.4 Test report .18
Annex A (informative) Five examples of marking systems for ribbed bars .19
Annex B (informative) Options for agreement between the manufacturer and purchaser .24
Bibliography .25
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 16, Steels for
the reinforcement and prestressing of concrete.
This fourth edition cancels and replaces the third edition (ISO 6935-2:2015), which has been technically
revised. The main changes compared to the previous edition are as follows:
— Figures 1, 2, 3 have been revised;
— Figure 5, A.3, A.4 have been newly added;
— introduction of hot-rolled threaded reinforcing bar in Clause 3, 4, 6 and A.7.
A list of all parts in the ISO 6935 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 6935-2:2019(E)
Steel for the reinforcement of concrete —
Part 2:
Ribbed bars
1 Scope
This document specifies technical requirements for ribbed bars to be used as reinforcement in concrete.
It is applicable to steel delivered in the form of bars, coils and de-coiled products. This document
covers both weldable and non-weldable steels. It does not apply to ribbed bars produced from finished
products, such as plates and railway rails.
The production process is at the discretion of the manufacturer.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/TR 9769, Steel and iron — Review of available methods of analysis
ISO 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical
composition
ISO 15630-1, Steel for the reinforcement and prestressing of concrete — Test methods — Part 1: Reinforcing
bars, rods and wire
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
cast analysis
chemical analysis representative of the cast determined by the manufacturer in accordance with its
own procedures
[SOURCE: ISO 16020:2005, 2.4.3, modified — “manufacturer” has replaced “steelmaker”.]
3.2
conformity assessment scheme
conformity assessment system related to specific objects of conformity assessment, to which the same
specified requirements, specific rules and procedures apply
Note 1 to entry: Conformity assessment schemes may be operated at an international, national or sub-national level.
Note 2 to entry: Certification, i.e. third-party attestation related to products, processes, systems or persons, is
applicable to all objects of conformity assessment except for conformity assessment bodies themselves, to which
accreditation is applicable.
3.3
characteristic value
value having a prescribed probability of not being attained in a hypothetical unlimited test series
Note 1 to entry: Equivalent to “fractile”, which is defined in ISO 3534-1:2006.
Note 2 to entry: A nominal value is used as the characteristic value in some circumstances.
[SOURCE: ISO 16020:2005, 2.4.10, modified —Note 2 to entry has been added.]
3.4
core
part of the cross section of a bar containing neither ribs nor indentations
[SOURCE: ISO 16020:2005, 2.2.5, modified — “wire” has been removed from the definition.]
3.5
ductility class
classification of the ductility properties of ribbed reinforcing bars based on the value of the ratio of
tensile strength to yield strength, as well as the elongation measured either as A or as A
gt
Note 1 to entry: See Table 6.
3.6
hot-rolled threaded reinforcing bar
type of bar with threaded geometry over its entire surface with two flat parts on the longitudinal side
Note 1 to entry: This type of bar with external threads is generally connected to other threaded bars with
internally threaded couplers.
3.7
longitudinal rib
uniform continuous rib parallel to the axis of a bar
[SOURCE: ISO 16020:2005, 2.2.7.1, modified — “wire” has been removed from the definition.]
3.8
nominal cross-sectional area
S
cross-sectional area equivalent to the area of a circular plain bar of the same nominal diameter
[SOURCE: ISO 16020:2005, 2.2.15, modified — “wire” has been removed from the definition.]
3.9
product analysis
chemical analysis carried out on the product
[SOURCE: ISO 16020:2005, 2.4.4]
3.10
relative rib area
f
R
area of the projections of all transverse ribs within a defined length on a plane perpendicular to the
longitudinal axis of the bar, divided by this length and the nominal circumference
[SOURCE: ISO 16020:2005, 2.2.11, modified — “wire” has been removed from the definition.]
2 © ISO 2019 – All rights reserved

3.11
rib height
a
distance from the highest point on the rib to the surface of the core measured perpendicular to the axis
of a bar
Note 1 to entry: See Figure 2.
[SOURCE: ISO 16020:2005, 2.2.12, modified — “highest point” has replaced “one point”, “perpendicular”
has replaced “normal”, “wire” has been removed from the definition and Note 1 to entry has been added.]
3.12
transverse rib spacing
c
distance between the centres of two consecutive transverse ribs (3.4) measured parallel to the axis
of a bar
Note 1 to entry: See Figure 1.
[SOURCE: ISO 16020:2005, 2.2.10, modified — “wire” has been removed from the definition.]
3.13
part of the circumference without rib
Σ
ei
sum of the distances along the surface of the core between the ends of the transverse ribs (3.4) of
adjacent rows measured as the projection on a plane perpendicular to the axis of a bar
[SOURCE: ISO 16020:2005, 2.2.13, modified — “or indentationless” has been removed from the term
and “or indentations” and “wire” have been removed from the definition.]
3.14
transverse rib
rib at an angle, either perpendicular or oblique, to the longitudinal axis of the bar
[SOURCE: ISO 16020:2005, 2.2.7.2, modified]
3.15
transverse rib flank inclination
α
angle between the flank of a transverse rib (3.4) and the core surface of a bar measured perpendicular
to the longitudinal axis of the transverse rib (3.4)
Note 1 to entry: See Figure 2.
[SOURCE: ISO 16020:2005, 2.2.9, modified — “wire” has been removed from the definition.]
3.16
transverse rib inclination
β
angle between the rib and the longitudinal axis of a bar
Note 1 to entry: See Figures 1, 3 and 4.
[SOURCE: ISO 16020:2005, 2.2.8, modified — “wire” has been removed from the definition.]
4 Symbols
For the purposes of this document, the symbols listed in Table 1 apply.
Table 1 — Symbols
Symbol Unit Description Reference
a mm Rib height 3.11, Clause 6
A % Percentage elongation after fracture 8.1
A % Percentage total extension at maximum force 8.1
gt
S mm Nominal cross-sectional area Clause 5, 9.1
b mm Top width of transverse rib at the mid-point Clause 6
c mm Transverse rib spacing 3.12, Clause 6
d mm Nominal diameter of the bar Clause 5, Clause 6, 9.3, 9.4,
Clause 10, 11.1,11.2,
Σ mm Part of the circumference without rib 3.13, Clause 6
ei
f — Required characteristic value 12.2, 12.3.2.3
k
f — Relative rib area 3.10, Clause 6
R
k, k' — Indices 12.3.2.3.1
m — Mean value of n individual values 12.3.2.3.1
n
n — Number of individual values 12.3.2.3.1
a
R MPa Upper yield strength 8.1
eH
a
R MPa Tensile strength 8.1
m
a
R MPa 0,2 % proof strength, plastic extension 8.1
p0,2
s — Standard deviation for n individual values 12.3.2.3.1
n
x — Individual value 12.3.2.3.1
i
α degree Transverse rib flank inclination 3.15, Clause 6
β degree Transverse rib inclination 3.16, Clause 6
T mm width of longitudinal flat part of hot-rolled threaded bar Clause 6
a 2
1 MPa = 1 N/mm .
5 Dimensions, mass per unit length and permissible deviations
Dimensions, mass per unit length and permissible deviations are given in Table 2. By agreement
between the manufacturer and purchaser, ribbed bars for which the nominal diameters are other than
those shown in Table 2 may be used. A list of options for agreement between the manufacturer and the
purchaser is provided in Annex B.
4 © ISO 2019 – All rights reserved

Table 2 — Dimensions, mass per unit length and permissible deviations
Nominal bar Nominal cross- Mass per unit length
a b
diameter sectional area
c
d S Requirement Permissible
d
deviation
mm mm kg/m %
6 28,3 0,222 ±8
8 50,3 0,395 ±8
10 78,5 0,617 ±6
12 113 0,888 ±6
14 154 1,21 ±5
16 201 1,58 ±5
20 314 2,47 ±5
25 491 3,85 ±4
28 616 4,84 ±4
32 804 6,31 ±4
40 1 257 9,86 ±4
50 1 964 15,42 ±4
a
Nominal diameters larger than 50 mm should be agreed between the manufacturer and
purchaser. The permissible deviation on mass for such bars shall be ±4 %.
b 2
S = 0,785 4 × d .
c −3
Mass per unit length = 7,85 × 10 × S .
d
Permissible deviation refers to a single bar.
The delivery length is subject to agreement between the manufacturer and purchaser.
NOTE Common delivery lengths of straight bars are 6 m, 9 m, 12 m and 18 m.
Unless otherwise agreed, the permissible deviation on delivery lengths from the rolling mill shall
+100
be mm.
6 Requirements for ribs
Ribbed bars shall have transverse ribs. Longitudinal ribs may be present or not.
There shall be at least two rows of transverse ribs equally distributed around the perimeter of the bar.
The transverse ribs within each row shall be distributed uniformly over the entire length of the bar,
except in the area of marking.
Ribs shall conform to the requirements given in Table 3.
Table 3 — Requirements for transverse ribs
Nominal bar Ribs of uniform Crescent-shaped
diameter height ribs
d
mm
Rib height, a
All 0,03d 0,03d
Minimum
Transverse rib spacing, c 6 ≤ d < 10 0,5d ≤ c ≤ 0,7d 0,5d ≤ c ≤ 1,0d
Range d ≥ 10 0,5d ≤ c ≤ 0,7d 0,5d ≤ c ≤ 0,8d
Table 3 (continued)
Nominal bar Ribs of uniform Crescent-shaped
diameter height ribs
d
mm
Transverse rib inclination, β All 35° ≤ β ≤ 90° 35° ≤ β ≤ 75°
Transverse rib flank inclination, α All α ≥ 40° α ≥ 40°
Part of the circumference without
rib, Σ All — 0,25dπ
ei
Maximum
Top width of transverse rib at the
6 ≤ d < 20 0,4d
mid-point, b 0,2d
d ≥ 20 0,2d
Maximum
Requirements for rib parameters may be specified by the relative rib area, or by agreement between
the manufacturer and purchaser. Measurement of rib parameters shall be performed in accordance
with ISO 15630-1.
Dimensions defining the rib geometry in Table 3 are shown in Figures 1 to 5.
When longitudinal ribs are present, their height shall not exceed 0,15d.
For transverse rib spacing of hot-rolled threaded bars, a minimum limit less than 0,5d may be agreed at
the time of enquiry and order, but the minimum limit shall not be less than 0,35d.
Key
1 longitudinal rib
2 transverse rib
Figure 1 — Ribbed bar — Definitions of geometry
6 © ISO 2019 – All rights reserved

Key
1 rib
2 rounded transition
Figure 2 — Rib flank inclination, α, rib height, a, and top width of transverse rib at the mid-
point, b — Section A-A from Figure 1
Figure 3 — Example of bar with varying rib inclinations to the longitudinal axis
Figure 4 — Example of bar with transverse ribs of uniform height (β = 90°)
3,,124××d 025
*maxT = ,minT =0
Figure 5 — Example of hot-rolled bar with threaded geometry and longitudinal flat part
7 Chemical composition
The chemical composition of the steel, as determined by cast analysis, shall conform to Table 4.
Calculate the carbon equivalent, CEV, according to Formula (1):
Mn (CrV++Mo) (CuN+ i)
CEVC=+ + + (1)
6 5 15
where C, Mn, Cr, V, Mo, Cu and Ni are the mass fractions, expressed as percentages of the respective
chemical elements of the steel.
In cases where product analysis is required, it shall be agreed at the time of enquiry and order. The
permissible deviation of the product analysis relative to the cast analysis as specified in Table 4 is given
in Table 5.
8 © ISO 2019 – All rights reserved

Table 4 — Chemical composition based on cast analysis — Maximum values of mass fractions,
in percentage
a, e b c b, d
Steel grade C Si Mn P S N CEV
B300A-R
B300B-R
B300C-R
B400A-R
B400B-R — — — 0,060 0,060 — —
B400C-R
B500A-R
B500B-R
B500C-R
B600A-R
B600B-R — — — 0,060 0,060 — —
B600C-R
B700A-R
B700B-R — — — 0,060 0,060 — —
B700C-R
B400AWR
B400BWR
B400CWR
0,22 0,60 1,60 0,050 0,050 0,012 0,50
B500AWR
B500BWR
B500CWR
B450AWR
0,22 — — 0,050 0,050 0,012 0,50
B450CWR
B300D-R — — — 0,050 0,050 — —
B300DWR 0,27 0,55 1,50 0,040 0,040 0,012 0,49
B350DWR 0,27 0,55 1,60 0,040 0,040 0,012 0,51
B400D-R 0,29 0,55 1,60 0,040 0,040 — 0,55
a
The first “B” stands for steel for reinforcing concrete. The next 3 digits represent the specified characteristic value of
minimum upper yield strength. The fifth symbol stands for ductility class. The sixth symbol relates to welding; “-” means
not intended for welding and “W” means intended for welding. The last “R” stands for ribbed bar.
b
For B400AWR, B400BWR, B400CWR, B500AWR, B500BWR and B500CWR with nominal diameters larger than 32 mm,
the maximum carbon content (C) is 0,25 % and the maximum carbon equivalent (CEV) is 0,55 %.
c
The maximum mass fraction of nitrogen may be 0,017%, if sufficient quantities of nitrogen-binding elements such as B,
Ti, Cr, Mo, V are intentionally added.
d
Other carbon equivalent (CEV) formulae and values may be used by agreement between the manufacturer and
purchaser.
e
Alloy elements, such as Cu, Ni, Cr, Mo, V, Nb, Ti and Zr, may be added by agreement between the manufacturer and
purchaser.
f
For B600D-R with nominal diameters larger than 32 mm. the maximum carbon content (c) is 0,40 % and the maximum
carbon equivalent (CEV) is 0,70 %.
g
If bars are manufactured purely by micro-alloying without quenching:
For B600D-R, the maximum C, Si and Mn shall be 0,45 %, 1,00 % and 2,00 % respectively.
The maximum carbon equivalent (CEV) shall be 0,58 % for B300DWR, 0,60 % for B350DWR, 0,65 % for B400D-R and
B400DWR, 0,66 % for B420DWR, 0,70 % for B500D-R and B500DWR, and 0,80 % for B600D-R.
Table 4 (continued)
a, e b c b, d
Steel grade C Si Mn P S N CEV
B400DWR 0,29 0,55 1,80 0,040 0,040 0,012 0,56
d
B420DWR 0,30 0,55 1,50 0,040 0,040 0,012 0,56
B500D-R 0,32 0,55 1,80 0,040 0,040 — 0,60
B500DWR 0,32 0,55 1,80 0,040 0,040 0,012 0,61
B600D-R 0,37 0,55 1,80 0,040 0,040 — 0,67
B700D-R 0,50 2,00 2,00 0,040 0,040 — 0,85
a
The first “B” stands for steel for reinforcing concrete. The next 3 digits represent the specified characteristic value of
minimum upper yield strength. The fifth symbol stands for ductility class. The sixth symbol relates to welding; “-” means
not intended for welding and “W” means intended for welding. The last “R” stands for ribbed bar.
b
For B400AWR, B400BWR, B400CWR, B500AWR, B500BWR and B500CWR with nominal diameters larger than 32 mm,
the maximum carbon content (C) is 0,25 % and the maximum carbon equivalent (CEV) is 0,55 %.
c
The maximum mass fraction of nitrogen may be 0,017%, if sufficient quantities of nitrogen-binding elements such as B,
Ti, Cr, Mo, V are intentionally added.
d
Other carbon equivalent (CEV) formulae and values may be used by agreement between the manufacturer and
purchaser.
e
Alloy elements, such as Cu, Ni, Cr, Mo, V, Nb, Ti and Zr, may be added by agreement between the manufacturer and
purchaser.
f
For B600D-R with nominal diameters larger than 32 mm. the maximum carbon content (c) is 0,40 % and the maximum
carbon equivalent (CEV) is 0,70 %.
g
If bars are manufactured purely by micro-alloying without quenching:
For B600D-R, the maximum C, Si and Mn shall be 0,45 %, 1,00 % and 2,00 % respectively.
The maximum carbon equivalent (CEV) shall be 0,58 % for B300DWR, 0,60 % for B350DWR, 0,
...