ASTM A944-22

Standard Test Method for Comparing Bond Strength of Steel Reinforcing Bars to Concrete Using Beam-End Specimens

ABSTRACT
This test method deals with the standard procedures for establishing the relative bond strength of steel reinforcing bars in concrete using beam-end specimens. This test method shall determine the effects of surface preparation or condition (such as bar coatings) on the bond strength of deformed steel reinforcing bars to concrete. The bond strengths obtained using this test method shall not be directly applicable to the design of reinforced concrete members. The beam-end test specimen shall be fabricated by casting, and conditioned by curing prior to tensile load test. The test system shall consist of the loading system, compression reaction plate, and bar displacement measurement device.
SCOPE
1.1 This test method describes procedures to establish the relative bond strength of steel reinforcing bars in concrete.  
1.2 This test method is intended to determine the effects of surface preparation or condition (such as bar coatings) on the bond strength of deformed steel reinforcing bars (of sizes ranging from No. 3 to No. 11 [No. 10 to No. 36]) to concrete.  
1.3 The bond strengths obtained using this test method are not directly applicable to the design of reinforced concrete members.
Note 1: The bond strengths obtained using this test method are generally higher than obtained in development or splice tests using beams with the same embedment lengths. The results obtained using this test method should only be used for comparisons with results for other reinforcing bars tested using this method.  
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in brackets are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
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.

General Information

• Status: Published
• Publication Date: 31-Aug-2022
• ICS: 91.080.13 - Steel structures
• Technical Committee: A01 - Steel, Stainless Steel and Related Alloys
• Drafting Committee: A01.05 - Steel Reinforcement

Relations

• Refers: ASTM E575-05(2018) - Standard Practice for Reporting Data from Structural Tests of Building Constructions, Elements, Connections, and Assemblies
• Effective Date: 01-Jul-2018
• Refers: ASTM C192/C192M-16 - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-Feb-2016
• Refers: ASTM C192/C192M-14 - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-Aug-2014
• Refers: ASTM E4-14 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2014
• Refers: ASTM C192/C192M-12a - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-Dec-2012
• Refers: ASTM E575-05(2011) - Standard Practice for Reporting Data from Structural Tests of Building Constructions, Elements, Connections, and Assemblies
• Effective Date: 01-Apr-2011
• Refers: ASTM E4-10 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jun-2010
• Refers: ASTM E4-09a - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Nov-2009
• Refers: ASTM E4-09 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Apr-2009
• Refers: ASTM E4-08 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Dec-2008
• Refers: ASTM C192/C192M-07 - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-Aug-2007
• Refers: ASTM E4-07 - Standard Practices for Force Verification of Testing Machines
• Effective Date: 01-Jan-2007
• Refers: ASTM C192/C192M-06 - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-Jun-2006
• Refers: ASTM E575-05 - Standard Practice for Reporting Data from Structural Tests of Building Constructions, Elements, Connections, and Assemblies
• Effective Date: 01-Oct-2005
• Refers: ASTM C192/C192M-05 - Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory
• Effective Date: 01-May-2005

Overview

ASTM A944-22: Standard Test Method for Comparing Bond Strength of Steel Reinforcing Bars to Concrete Using Beam-End Specimens defines a standardized procedure for evaluating the relative bond strength between steel reinforcing bars and concrete. The method uses beam-end specimens to analyze how surface preparation or conditions-including bar coatings-impact the adherence of deformed steel reinforcing bars to concrete. This standard supports researchers, manufacturers, and quality control professionals in comparing the performance of different reinforcement materials and coatings under controlled laboratory conditions.

Key Topics

• Relative Bond Strength Assessment
  Determines and compares the bond strength of steel reinforcing bars embedded in concrete, focusing on variables such as surface preparation and bar coatings.
• Specimen Preparation
  Describes fabrication of beam-end concrete specimens with embedded deformed bars (sizes No. 3 to No. 11), including concrete casting, reinforcement arrangement, and curing processes.
• Testing Procedure
  Outlines the use of a loading system, compression reaction plate, and precise displacement measurement devices (e.g., dial gauges or LVDTs) to conduct tensile bond tests.
• Reporting Requirements
  Specifies essential data points for reporting, such as bar and concrete properties, specimen details, load/displacement results, and observed failure modes.
• Limitations
  Clarifies that bond strength results from this method are for comparative evaluation only and not directly applicable to design calculations for reinforced concrete members.

Applications

ASTM A944-22 is valuable in several practical contexts related to construction and materials development:

• Quality Control for Rebar Manufacturing
  Enables assessment of manufacturing processes or surface treatments (such as epoxy coatings), ensuring that reinforced bars meet performance expectations regarding bond to concrete.
• Research and Development
  Facilitates comparative studies on new bar coatings, surface preparations, or innovative concrete mixes, supporting advancements in reinforced concrete technology.
• Product Certification
  Provides standardized procedures for certifying the relative performance of steel reinforcing bars according to bond strength, aiding regulatory compliance and market acceptance.
• Specification Compliance Testing
  Useful for verifying product claims regarding surface treatments or coatings as specified in purchasing or project requirements.
• Educational and Training Resource
  Serves as an instructional tool for laboratories, universities, and training organizations involved in testing the bond interaction between steel reinforcement and concrete.

Related Standards

Organizations and professionals utilizing ASTM A944-22 may also reference several related ASTM standards, including:

• ASTM C192/C192M: Practice for Making and Curing Concrete Test Specimens in the Laboratory
  Outlines procedures for creating representative concrete specimens for laboratory testing.
• ASTM E4: Practices for Force Calibration and Verification of Testing Machines
  Ensures accuracy in equipment used to measure applied loads during testing.
• ASTM E575: Practice for Reporting Data from Structural Tests of Building Constructions, Elements, Connections, and Assemblies
  Guides the comprehensive and standardized reporting of structural test results.
• Reinforced Concrete Standards: Consult additional ASTM and ACI documents for design, construction, and testing requirements of reinforced concrete members.

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Keywords: ASTM A944, bond strength of steel reinforcing bars, concrete bond test, beam-end specimen test, rebar coatings, rebar surface preparation, comparative bond strength, laboratory testing, quality control for reinforcing steel, concrete reinforcement standards.

Standards Content (Sample)

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.
Designation: A944 − 22
Standard Test Method for
Comparing Bond Strength of Steel Reinforcing Bars to
Concrete Using Beam-End Specimens
This standard is issued under the fixed designation A944; 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.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method describes procedures to establish the
C192/C192M Practice for Making and Curing Concrete Test
relative bond strength of steel reinforcing bars in concrete.
Specimens in the Laboratory
1.2 This test method is intended to determine the effects of
E4 Practices for Force Calibration and Verification of Test-
surface preparation or condition (such as bar coatings) on the
ing Machines
bond strength of deformed steel reinforcing bars (of sizes
E575 Practice for Reporting Data from Structural Tests of
ranging from No. 3 to No. 11 [No. 10 to No. 36]) to concrete. Building Constructions, Elements, Connections, and As-
semblies
1.3 The bond strengths obtained using this test method are
not directly applicable to the design of reinforced concrete
3. Terminology
members.
3.1 Definitions of Terms Specific to This Standard:
3.1.1 bond strength, n—maximum measured load in a ten-
NOTE 1—The bond strengths obtained using this test method are
sile bond test of a steel reinforcing bar.
generally higher than obtained in development or splice tests using beams
with the same embedment lengths. The results obtained using this test
3.1.2 bonded length, n—the length of the test bar that is in
method should only be used for comparisons with results for other
contact with concrete.
reinforcing bars tested using this method.
3.1.3 concrete cover, n—minimum distance between the
1.4 The values stated in inch-pound units are to be regarded
surface of the test bar and the top or bottom of the test
as standard. The values given in brackets are mathematical
specimen.
conversions to SI units that are provided for information only
3.1.4 embedment length, n—the distance from the surface of
and are not considered standard.
the concrete test specimen to the installed end of the steel
1.5 This standard does not purport to address all of the reinforcing bar. This equals the sum of the lead length and the
safety concerns, if any, associated with its use. It is the bonded length.
responsibility of the user of this standard to establish appro-
3.1.5 lead length, n—the length of the test bar that is not in
priate safety, health, and environmental practices and deter-
contact with concrete but is between the surface of the concrete
mine the applicability of regulatory limitations prior to use.
test specimen and the bonded length.
1.6 This international standard was developed in accor-
3.1.6 relative rib area, n—ratio of the projected rib area
dance with internationally recognized principles on standard-
normal to bar axis to the product of the nominal bar perimeter
ization established in the Decision on Principles for the
and the center-to-center rib spacing.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
This test method 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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Sept. 1, 2022. Published November 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1995. Last previous edition approved in 2015 as A944 – 10 (2015). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/A0944-22. the ASTM website.
*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
A944 − 22
3.2 Symbols: 4.3 BarDisplacementMeasurements—Displacementsofthe
C = Concrete cover, in. [mm]. loaded and free ends of the steel reinforcing bar shall be
c
d = Nominal diameter of reinforcing bar, in. [mm]. measured with respect to the loaded and free surfaces,
b
ℓ = Embedment length, in. [mm]. respectively, of the concrete using suitable measurement de-
e
vices. Dial gages having the smallest division of not more than
4. Apparatus
0.001 in. [25 µm] or linear variable differential transformers
(LVDTs) with equal or superior accuracy are examples of
4.1 Equipment—A schematic of a suitable testing system is
shown in Fig. 1. The loading system shall be capable of satisfactory devices.
measuring the forces to an accuracy within 62 % of the
applied load, when calibrated in accordance with Practices E4. 5. Test Specimen
The test system shall have sufficient capacity to prevent
5.1 Beam-EndSpecimen—Thetestspecimenshallconsistof
yielding of its various components and shall ensure that the
the test bar cast in reinforced concrete 24 in. 6 1 in. [600 mm
applied tensile force remains parallel to the axis of the steel
6 25 mm] long by d +8 6 ⁄2 in. [d + 200 6 13 mm] wide
b b
reinforcing bar during testing.
by a minimum of d +C + ℓ +2 ⁄2 in. [d +C + ℓ +60mm]
b c e b c e
4.2 Compression Reaction Plate—The compression reac- high. A typical test specimen shown in casting position is
tionplateshallbeplacedaminimumcleardistanceequalto0.9 illustrated in Fig. 2. Specimens are inverted prior to testing.
times the embedment length (ℓ ) measured from the center of The specimen shall be reinforced by four closed stirrups
e
the test bar to the edge of the reaction plate. oriented parallel to the sides of the specimen and two flexural
FIG. 1 Schematic of Test Apparatus
A944 − 22
FIG. 2 Beam-End Test Specimens in Casting Position
NOTE 2—Alternatively, the interior PVC pipe may be extended to the
steel reinforcing bars parallel to the test bar, as shown in Fig.
back of the specimen.
2. Transverse steel reinforcing bars similar to those illustrated
NOTE 3—The lead length, shown in Fig. 2, is typically between 0.5 in.
in Fig. 2 may be used to aid in fabrication and testing. The test
and 4 in. [13 mm and 100 mm]. This unbonded region is used to prevent
bar shall extend from the front surface a distance that is
a cone-type pullout failure at the surface of the concrete. Increases in lead
compatible with the test system.Two polyvinyl chloride (PVC)
length generally result in an increase in bond strength.
pipes shall be used as bond breakers to control the bonded
5.2 Fabrication—Unless otherwise specified, the concrete
length of the bar and to avoid a localized cone-type failure of
block shall be fabricated using concrete designed to produce a
the concrete at the loaded end of the specimen. The PVC pipes
strength at the time of test between 4500 psi and 5500 psi
shall be sized so as to minimize the gap between the test bar
[31 MPa and 38 MPa]. The specimen shall be cast in approxi-
and pipe wall, and the gap between the PVC pipe and test bar
mately equal layers not exceeding 9 in. [230 mm] in depth.
shall be caulked or otherwise sealed to prevent concrete from
Each layer shall be adequately consolidated with an internal
flowing into the pipes. The free end of
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: A944 − 10 (Reapproved 2015) A944 − 22
Standard Test Method for
Comparing Bond Strength of Steel Reinforcing Bars to
Concrete Using Beam-End Specimens
This standard is issued under the fixed designation A944; 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.
1. Scope Scope*
1.1 This test method describes procedures to establish the relative bond strength of steel reinforcing bars in concrete.
1.2 This test method is intended to determine the effects of surface preparation or condition (such as bar coatings) on the bond
strength of deformed steel reinforcing bars (of sizes ranging from No. 103 to No. 3611 [No. 310 to No. 11])36]) to concrete.
1.3 The bond strengths obtained using this test method are not directly applicable to the design of reinforced concrete members.
NOTE 1—The bond strengths obtained using this test method are generally higher than obtained in development or splice tests using beams with the same
embedment lengths. The results obtained using this test method should only be used for comparisons with results for other reinforcing bars tested using
this method.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in brackets are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
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.
2. Referenced Documents
2.1 ASTM Standards:
A775/A775M Specification for Epoxy-Coated Steel Reinforcing Bars
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
E4 Practices for Force Calibration and Verification of Testing Machines
E575 Practice for Reporting Data from Structural Tests of Building Constructions, Elements, Connections, and Assemblies
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
This test method 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, 2015Sept. 1, 2022. Published November 2015November 2022. Originally approved in 1995. Last previous edition approved in 20102015
as A944 – 10.A944 – 10 (2015). DOI: 10.1520/A0944-10R15.10.1520/A0944-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
A944 − 22
3.1.1 bond strength, n—maximum measured load in a tensile bond test of a steel reinforcing bar.
3.1.2 bonded length, n—the length of the test bar that is in contact with concrete.
3.1.3 concrete cover, n—minimum distance between the surface of the test bar and the top or bottom of the test specimen.
3.1.4 embedment length, n—the distance from the surface of the concrete test specimen to the installed end of the steel reinforcing
bar. This equals the sum of the lead length and the bonded length.
3.1.5 lead length, n—the length of the test bar that is not in contact with concrete but is between the surface of the concrete test
specimen and the bonded length.
3.1.6 relative rib area, n—ratio of the projected rib area normal to bar axis to the product of the nominal bar perimeter and the
center-to-center rib spacing.
A944 − 22
3.2 Symbols:
C = Concrete cover, mm [in.].in. [mm].
bc
d = Nominal diameter of reinforcing bar, mm [in.].in. [mm].
b
lℓ = Embedment length, mm [in.].in. [mm].
e
4. Apparatus
4.1 Equipment—A schematic of a suitable testing system is shown in Fig. 1. The loading system shall be capable of measuring
the forces to an accuracy within 62 % of the applied load, when calibrated in accordance with Practices E4. The test system shall
have sufficient capacity to prevent yielding of its various components and shall ensure that the applied tensile loadforce remains
parallel to the axis of the steel reinforcing bar during testing.
4.2 Compression Reaction Plate—The compression reaction plate shall be placed a minimum clear distance equal to 0.9 ltimes
the embedment length (ℓ ) measured from the center of the test bar to the edge of the reaction plate.
e
4.3 Bar Displacement Measurements—Displacements of the loaded and free ends of the steel reinforcing bar shall be measured
FIG. 1 Schematic of Test Apparatus
A944 − 22
with respect to the loaded and free surfaces, respectively, of the concrete using suitable measurement devices. Dial gages having
the smallest division of not more than 25 μm [0.001 in.] 0.001 in. [25 μm] or linear variable differential transformers (LVDTs) with
equal or superior accuracy are examples of satisfactory devices.
5. Test Specimen
5.1 Beam-End Specimen—The test specimen shall consist of the test bar cast in a block of reinforced concrete 600 6 25 mm [24
1 1
6 1 in.]24 in. 6 1 in. [600 mm 6 25 mm] long by d + 2008 6 13 ⁄2 mmin. [d + 8200 6 ⁄2 in.]13 mm] wide by a minimum
b b
1 1
of d + C + lℓ + 602 ⁄2 mmin. [d + C + lℓ + 260 ⁄2 in.]mm] high. A typical test specimen shown in casting position is
b bc e b bc e
illustrated in Fig. 2. Specimens are inverted prior to testing. The specimen shall be reinforced by four closed stirrups oriented
parallel to the sides of the specimen and two flexural steel reinforcing bars parallel to the test bar, as shown in Fig. 2. Transverse
steel reinforcing bars similar to those illustrated in Fig. 2 may be used to aid in fabrication and testing. The test bar shall extend
from the front surface a distance that is compatible with the test system. Two polyvinyl chloride (PVC) pipes shall be used as bond
breakers to control the bonded length of the bar and to avoid a localized cone-type failure of the concrete at the loaded end of the
specimen. The PVC pipes shall be sized so as to minimize the gap between the test bar and pipe wall, and the gap between the
PVC pipe and test bar shall be caulked or otherwise sealed to prevent concrete from flowing into the pipes. The free end of the
test bar shall butt against a hollow steel conduit or other device to provide access to the free end for measuring slip during the test;
alternatively, access to the free end of the test bar shall be provided without the hollow steel conduit by extending the interior PVC
pipe and test bar to the end of the specimen. All specimens in a test series shall use the same method to provide access to the free
end of the bar. The closed stirrups shall be fabricated from Grade 42060 [Grade 60]420] No. 103 [No. 3]10] bars for test bars up
to and including No. 258 [No. 8]25] and No. 134 [No. 4]13] bars for test bars larger than No. 258 [No. 8].25]. The two flexural
steel reinforcing bars shall be selected so as to provide a total area not less than that of the test bar.
NOTE 2—Alternatively, the interior PVC pipe may be extended to the back of the
...