ASTM D8337/D8337M-21

Standard Test Method for Evaluation of Bond Properties of FRP Composite Applied to Concrete Substrate using Single-Lap Shear Test

SIGNIFICANCE AND USE
5.1 This test method is intended for use in a laboratory setting.  
5.2 This test method is used to evaluate the plateau force Ppl that an FRP composite can bear before complete debonding from a concrete prism.  
5.3 The evaluation of the plateau force is intended to be made under consistent environmental conditioning and the tests conducted in ambient laboratory or otherwise consistent environmental conditions.  
5.4 This test can be used to determine the effective bond length leff of the FRP composite if different bonded lengths are tested with constant bonded width. The effective bond length leff is defined as the minimum bonded length  necessary to achieve the bond capacity Ppl for the width of FRP tested.  
5.5 This test can be used to determine the variation of the bond capacity with the bonded width bf if different bonded widths are tested while the bonded length  is constant and greater than the effective bond length leff.  
5.6 This test is used to obtain the plot of the applied force versus loaded end (or global) slip of the composite with respect to the substrate. The loaded end slip is the average of two linear variable differential transformer (LVDT) readings, as described in 7.6. The plot obtained is used to determine the bond properties of the system.  
5.7 This test method can also serve as a means for uniformly preparing and testing standard specimens suitable for being subject to environmental conditioning and subsequently used to evaluate FRP-bonded-to-concrete system performance, and evaluating and reporting the results. The comparison of results from this test method conducted on identical specimens subject to different environmental conditioning protocols can be used to evaluate the effects of environmental exposure on the bond performance of FRP systems.
SCOPE
1.1 This test method describes the apparatus and procedure to evaluate the lap shear bond properties of wet lay-up or shop-fabricated (for example, pultruded) fiber-reinforced polymer (FRP) composite systems adhesively applied to a flat concrete substrate. The test determines the plateau force that an FRP system can bear before complete debonding from a concrete prism tested using a direct single-lap shear test. This plateau force is reported as bond capacity and may be different from the maximum applied force. The plateau force is then used to determine the interfacial fracture energy and the cohesive material law.  
1.2 This test method is not intended for job approval or for product qualification purposes unless an external agency adopts the test method for those purposes.  
1.3 This test method is intended for use with adhesive-applied or wet lay-up FRP systems and is appropriate for use with FRP systems having any fiber orientation or combination of ply orientations comprising the FRP composite, although the test condition only considers forces in the direction parallel to the prism longitudinal axis.  
1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.4.1 Within the text, the inch-pound units are shown in brackets.  
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 Barrier...

General Information

• Status: Published
• Publication Date: 31-Dec-2020
• ICS: 59.100.01 - Materials for the reinforcement of composites in general
• Technical Committee: D30 - Composite Materials
• Drafting Committee: D30.10 - Composites for Civil Structures

Relations

• Refers: ASTM C31/C31M-24a - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Apr-2024
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM C31/C31M-24 - Standard Practice for Making and Curing Concrete Test Specimens in the Field
• Effective Date: 01-Jan-2024
• Refers: ASTM C39/C39M-23 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
• Effective Date: 01-Dec-2023
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM C617/C617M-23 - Standard Practice for Capping Cylindrical Concrete Specimens
• Effective Date: 01-Oct-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E251-20a - Standard Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
• Effective Date: 01-Jun-2020
• Refers: ASTM E251-20 - Standard Test Methods for Performance Characteristics of Metallic Bonded Resistance Strain Gages
• Effective Date: 01-May-2020
• Refers: ASTM D5229/D5229M-20 - Standard Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials
• Effective Date: 01-Mar-2020
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM C125-19a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 15-Dec-2019
• Refers: ASTM D3878-19a - Standard Terminology for Composite Materials
• Effective Date: 15-Oct-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019

Overview

ASTM D8337/D8337M-21 provides a standardized laboratory method for evaluating the bond properties of fiber-reinforced polymer (FRP) composite systems adhesively applied to concrete substrates using a single-lap shear test. Developed by ASTM Committee D30, this standard aims to assess the lap shear bond strength-also referred to as plateau force-of various FRP composites when bonded to concrete under controlled environmental conditions. The results from this test are used to determine critical values such as bond capacity, effective bond length, and the influence of bonded width on system performance.

This test method is suitable for both wet lay-up and shop-fabricated (pultruded) FRP systems and is adaptable to any fiber orientation or ply arrangement applied to flat concrete surfaces. While primarily intended for laboratory evaluation, the test can also assist in research and comparative studies where standardized specimen preparation and results are essential. The outcomes help in understanding material performance, especially in relation to environmental exposure and design considerations for retrofitting or structural reinforcement.

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Key Topics

• Bond Capacity Evaluation: The method determines the plateau force (Ppl), the maximum force an FRP composite can handle before complete debonding from concrete.
• Effective Bond Length: By testing different bonded lengths, the minimum length needed to reach bond capacity for a given width is identified.
• Influence of Bonded Width: Assesses how changes in the width of FRP bonded to concrete affect the bond strength, assuming bonded length is constant and sufficient.
• Force–Slip Relationship: The applied force versus loaded end slip is plotted to derive the bond properties of the FRP-concrete system using precise LVDT instrumentation.
• Environmental Conditioning: The method standardizes how specimens can be conditioned to evaluate effects such as moisture, temperature, or chemical exposure on bond performance.
• Failure Modes: The standard identifies valid and invalid failure modes, ensuring that only cohesive failures in the concrete substrate are considered indicative of proper bond performance.

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Applications

• Structural Assessment: Used by engineers and researchers to evaluate FRP-to-concrete bond performance, crucial for design and assessment of strengthening systems for bridges, buildings, and infrastructure.
• Material Development: Supports manufacturers and developers in comparing new or modified FRP systems or adhesives under consistent laboratory conditions.
• Quality Control and Research: Provides a basis for conducting comparative studies on how factors such as adhesive type, fiber orientation, environmental exposure, and surface preparation influence bond properties.
• Performance Evaluation: Enables analysis of long-term behavior of FRP-concrete systems after exposure to environmental stresses, assisting in durability assessments and service-life predictions.
• Education and Training: Offers a standardized framework for academic and professional training on material characterization in civil and structural engineering contexts.

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Related Standards

• ASTM C31/C31M: Practice for Making and Curing Concrete Test Specimens in the Field
• ASTM C33/C33M: Specification for Concrete Aggregates
• ASTM C39/C39M: Test Method for Compressive Strength of Cylindrical Concrete Specimens
• ASTM C42/C42M: Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
• ASTM D3039/D3039M: Test Method for Tensile Properties of Polymer Matrix Composite Materials
• ASTM D7565/D7565M: Test Method for Tensile Properties of Fiber Reinforced Polymer Matrix Composites Used for Strengthening of Civil Structures
• ASTM D5229/D5229M: Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Matrix Composite Materials

For complete and up-to-date related standards, visit the ASTM International website.

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By following ASTM D8337/D8337M-21, stakeholders ensure consistency and reliability in the evaluation of FRP-concrete bond systems, supporting advances in civil infrastructure durability, maintenance, and safety. This standard is fundamental for laboratories, material developers, civil engineers, and researchers seeking to optimize the bond performance of FRP composites in concrete strengthening applications.

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: D8337/D8337M − 21
Standard Test Method for
Evaluation of Bond Properties of FRP Composite Applied to
Concrete Substrate using Single-Lap Shear Test
This standard is issued under the fixed designation D8337/D8337M; 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 ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method describes the apparatus and procedure
mendations issued by the World Trade Organization Technical
to evaluate the lap shear bond properties of wet lay-up or
Barriers to Trade (TBT) Committee.
shop-fabricated (for example, pultruded) fiber-reinforced poly-
mer (FRP) composite systems adhesively applied to a flat
2. Referenced Documents
concretesubstrate.Thetestdeterminestheplateauforcethatan
FRP system can bear before complete debonding from a 2.1 ASTM Standards:
concrete prism tested using a direct single-lap shear test. This C31/C31MPractice for Making and Curing Concrete Test
plateau force is reported as bond capacity and may be different Specimens in the Field
from the maximum applied force. The plateau force is then C33/C33MSpecification for Concrete Aggregates
used to determine the interfacial fracture energy and the C39/C39MTest Method for Compressive Strength of Cylin-
cohesive material law. drical Concrete Specimens
C42/C42MTest Method for Obtaining and Testing Drilled
1.2 This test method is not intended for job approval or for
Cores and Sawed Beams of Concrete
product qualification purposes unless an external agency
C125Terminology Relating to Concrete and Concrete Ag-
adopts the test method for those purposes.
gregates
1.3 This test method is intended for use with adhesive-
C150/C150MSpecification for Portland Cement
applied or wet lay-up FRP systems and is appropriate for use
C192/C192MPracticeforMakingandCuringConcreteTest
with FRPsystems having any fiber orientation or combination
Specimens in the Laboratory
ofplyorientationscomprisingtheFRPcomposite,althoughthe
C496/C496MTest Method for Splitting Tensile Strength of
test condition only considers forces in the direction parallel to
Cylindrical Concrete Specimens
the prism longitudinal axis.
C511Specification for Mixing Rooms, Moist Cabinets,
Moist Rooms, and Water Storage Tanks Used in the
1.4 Units—The values stated in either SI units or inch-
pound units are to be regarded separately as standard. The Testing of Hydraulic Cements and Concretes
C617/C617MPractice for Capping Cylindrical Concrete
values stated in each system are not necessarily exact equiva-
lents; therefore, to ensure conformance with the standard, each Specimens
D883Terminology Relating to Plastics
system shall be used independently of the other, and values
from the two systems shall not be combined. D3039/D3039MTest Method forTensile Properties of Poly-
mer Matrix Composite Materials
1.4.1 Within the text, the inch-pound units are shown in
brackets. D3878Terminology for Composite Materials
D5229/D5229MTestMethodforMoistureAbsorptionProp-
1.5 This standard does not purport to address all of the
erties and Equilibrium Conditioning of Polymer Matrix
safety concerns, if any, associated with its use. It is the
Composite Materials
responsibility of the user of this standard to establish appro-
D7565/D7565MTest Method for DeterminingTensile Prop-
priate safety, health, and environmental practices and deter-
erties of Fiber Reinforced Polymer Matrix Composites
mine the applicability of regulatory limitations prior to use.
Used for Strengthening of Civil Structures
1.6 This international standard was developed in accor-
D7958/D7958MTestMethodforEvaluationofPerformance
dance with internationally recognized principles on standard-
This test method is under the jurisdiction of ASTM Committee D30 on
Composite Materials and is the direct responsibility of Subcommittee D30.10 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Composites for Civil Structures. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Jan. 1, 2021. Published May 2021. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D8337_D8337M-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8337/D8337M − 21
for FRP Composite Bonded to Concrete Substrate using P —applied force corresponding to 15% of P
15% pl
Beam Test P —applied force corresponding to 35% of P
35% pl
E4Practices for Force Verification of Testing Machines s—slip between the faces of the interfacial crack
E6Terminology Relating to Methods of Mechanical Testing s—slip s corresponding to the complete separation of the
f
E122PracticeforCalculatingSampleSizetoEstimate,With faces of the interfacial crack
Specified Precision, the Average for a Characteristic of a s —slip s corresponding to the maximum shear stress τ
m max
Lot or Process S —sample standard deviation
N-1
E251Test Methods for Performance Characteristics of Me- t—machine stroke
tallic Bonded Resistance Strain Gages v—distancebetweentheaxisofLVDTAorLVDTBandthe
E456Terminology Relating to Quality and Statistics edge of the FRP strip
w —displacement measured by LVDT C
c
3. Terminology
w —displacement measured by LVDT D
d
x—measured or derived property
i
3.1 Definitions—Terminology D3878 defines terms relating
z—horizontal distance between LVDT C and LVDT D
to high-modulus fibers and their composites. Terminology
z —distance between point of reaction of LVDT C and
D883definestermsrelatingtoplastics.TerminologyE6defines
LVDT D and the bottom plate
termsrelatingtomechanicaltesting.TerminologyC125defines
ɛ —debonding strain in the FRP corresponding to P
pl pl
terms relating to concrete. Terminology E456 and Practice
ɛ —longitudinal strain component in the FRP strip (in the
E122 define terms relating to statistics. In the event of a yy
direction of the axis of the prism)
conflict between terms, Terminology D3878 shall have prece-
τ—interfacial shear stress
dence over the other standards.
τ —maximum interfacial shear stress
max
3.2 Symbols:
a—distance between the top plate and the edge of the
4. Summary of Test Method
concrete prism
4.1 The direct single-lap shear test is conducted using a
c—width of the top flange of the Ω-shaped plate
push-pull configuration, where the concrete prism with square
c —length of the web of the Ω-shaped plate
or rectangular cross-section is restrained while the composite
c —width of the bottom flange of the Ω-shaped plate
stripispulleduntilfailure.FRPreinforcementisbondedtoone
b—width of test concrete prism
face of the concrete prism. Because the formed faces of the
b—bonded width of FRP
f
concrete prism might have a different amount of aggregates
CV—sample coefficient of variation
near the surface, the face to which the FRP composite is
d—overall depth of test concrete prism
applied with respect to the casting orientation shall be clearly
d —bond break, that is, distance between the beginning of
f
identified in the report. Neither the troweled (Practice C192/
the bonded area and the top edge (at loaded end of the
C192M) longitudinal face nor the square (or rectangular) ends
composite strip) of the concrete prism
of the concrete prism shall be used to bond the FRPreinforce-
E —modulus of elasticity of concrete
c
ment.
chord
E —tensilechordmodulusofelasticityofpultrudedFRP
(Test Method D3039/D3039M)
5. Significance and Use
fˊ —compressive strength of concrete
c
5.1 This test method is intended for use in a laboratory
fˊ—splitting tensile strength of concrete
t
setting.
g—global slip (or loaded end slip) as measured by LVDTs
5.2 Thistestmethodisusedtoevaluatetheplateauforce P
g —global slip corresponding to P in the load re- pl
15% 15%
that an FRP composite can bear before complete debonding
sponse
from a concrete prism.
g —global slip corresponding to P in the load re-
35% 35%
sponse
5.3 The evaluation of the plateau force is intended to be
G —interfacial fracture energy
F made under consistent environmental conditioning and the
h—thickness of pultruded FRP
tests conducted in ambient laboratory or otherwise consistent
k—slope of the linear ascending branch of the cohesive
environmental conditions.
material law
5.4 This test can be used to determine the effective bond
K*—chord tensile stiffness of wet-layup composite (Test
length l of the FRPcomposite if different bonded lengths are
eff
Method D7565/D7565M)
tested with constant bonded width. The effective bond length
ℓ—bonded length of FRP
l is defined as the minimum bonded length ℓ necessary to
eff
L—length of test concrete prism
achieve the bond capacity P for the width of FRP tested.
pl
L—total length of the FRP composite strip
f
5.5 This test can be used to determine the variation of the
l —effective bond length
eff
bond capacity with the bonded width b if different bonded
f
N—number of specimens
widths are tested while the bonded length ℓ is constant and
n—number of plies (that is, number of layers of fibers)
greater than the effective bond length l .
eff
P —maximum applied force indicated by testing machine
max
P —plateau force, named also bond capacity, associated 5.6 This test is used to obtain the plot of the applied force
pl
with propagation of the debonding until complete separation versusloadedend(orglobal)slipofthecompositewithrespect
D8337/D8337M − 21
tothesubstrate.Theloadedendslipistheaverageoftwolinear 7. Apparatus
variabledifferentialtransformer(LVDT)readings,asdescribed
7.1 Micrometers and Calipers—Micrometers used to deter-
in 7.6. The plot obtained is used to determine the bond
mine specimen dimensions shall use a suitable size diameter
properties of the system.
ball-interface on irregular surfaces and a flat anvil interface on
5.7 Thistestmethodcanalsoserveasameansforuniformly machined edges or very-smooth tooled surfaces. For typical
preparing and testing standard specimens suitable for being
specimengeometries,theaccuracyoftheinstrument(s)shallbe
subject to environmental conditioning and subsequently used suitable for reading to within1%ofthe intended measure-
to evaluate FRP-bonded-to-concrete system performance, and
ment.The use of alternative measurement devices is permitted
evaluating and reporting the results.The comparison of results if specified (or agreed to) by the test requestor and reported by
fromthistestmethodconductedonidenticalspecimenssubject
the testing laboratory.
to different environmental conditioning protocols can be used
7.2 Dimensional Tolerances—Dimensional tolerances for
to evaluate the effects of environmental exposure on the bond
the components of the test fixture produced in U.S. customary
performance of FRP systems.
units shall be standard tolerances as follows: Unless noted
otherwise on the drawings, dimensions given to one decimal
6. Interferences
place (0.X in.) shall be 60.05in., dimensions given to two
6.1 Material and Specimen Preparation—Non-uniform
decimal places (0.0X in.) shall be 60.01 in., and dimensions
FRP thickness or FRP-to-substrate adhesive thickness can
given to three decimal places (0.00X in.) shall be 60.005in.
affectanindividualtestresultandintroducebiasedorscattered
For components produced in SI units, standard tolerances for
test results.
dimensions given to zero decimal places (Xmm) shall be
6.1.1 Surface Preparation—Concrete surface may be sand-
61mm, dimensions given to one decimal place (0.Xmm)
blasted or abraded as per the FRP manufacturer’s recommen-
shall be 60.25mm, dimensions given to two decimal places
dation. Variation of roughness of the concrete surface between
(0.0Xmm) shall be 60.1mm.
specimens can cause biased or scattered results
7.3 The testing machine used shall conform to the require-
6.1.2 Specimen aging and conditioning affect the concrete
mentsofthesectionsonBasisofVerification,Corrections,and
strength and modulus as well as the epoxy strength and
Time Interval Between Verifications of Practices E4. Hand
modulus, which may affect the stress transfer at the FRP-
operated testing machines having pumps that do not provide a
concrete interface and therefore the plateau force.
continuous loading in one stroke are not permitted. Motorized
6.2 Specimen Dimensions—This method calculates a value
pumps or hand operated positive displacement pumps having
of force required to debond completely the FRP composite
sufficient volume in one continuous stroke to complete a test
from the concrete substrate; as such, results are dependent on
without requiring replenishment are permitted and shall be
the specimen dimensions. Unless this test is used to determine
capable of applying loads at a uniform rate without shock or
the effective bond length or the effect of the bonded width,
interruption.
comparing values calculated using specimens having different
7.4 Loading Apparatus—Tests are conducted using a direct
dimensions should not be done.
single-lap shear test set-up.
6.3 FRP Reinforcement—A bonded area of the composite
7.4.1 The concrete prism is restrained against movement by
that is wider than two thirds of the prism width or longer than
two steel plates placed against the square (or rectangular) end
four fifths of the length of the concrete prism can be sufficient
cross-sections of the concrete prism (Fig. 1). The centroid of
to cause spalling of the concrete prism because of the unre-
the bottom plate must be aligned with the axis of the machine.
strained shear deformation near the edges of the prism (see
The top plate is connected to the bottom plate through four
11.10.3). Testing widths larger than two thirds of the prism
threaded steel bars bolted to the two plates. In order to ensure
width might be of interest, as it could identify effects relevant
adequate stiffness, an additional plate (stiffener) could be
to retrofit of thin-stemmed beams; however, if spalling occurs
weldedperpendicularlytothetopplate.AppendixX1provides
prior to debonding of the FRP strip, it will result in an invalid
recommendeddimensionsthatcanbeconsideredasareference
test as per the scope of this standard.The number of plies may
when one ply of FRP is applied and the 28-day compressive
causeadifferentfailuremodeindependentofthedimensionsof
strength fˊ of the cylinders falls between 22 to 55MPa [3200
c
the bonded area
to 8000 psi] (see 8.4.3). It is recommended that the top plate
has a distance a from the edge of the concrete prism equal to
6.4 Splitting of the FRP strip lengthwise prior to bond
or greater than 25 mm [1in.] to avoid high compressive
failure should be considered an interference, which invalidates
stresses close to the FRP-concrete interface.
the results.
7.5 The stroke of the testing machine and the applied force
6.5 Test Rate—A change of the test rate among specimens
shall be recorded continuously during the test.
may invalidate the results, as the interfacial properties can be
rate dependent.
7.6 Slip Measurement—Two linear variable differential
6.6 Adhesive failure (see 11.10.1.2), cohesive failure in transformers(LVDTs)shallbemountedontheconcretesurface
either adhesive or FRP material (see 11.10.1.3), and FRP bymeansoftwoaluminumholdersthatareplacedoneachside
rupture failure (see 11.10.2) should be considered of the FRP strip at the top edge of the bonded region. The
interferences, which invalidate the results. holder is a prismatic aluminum block with a central hole to fit
D8337/D8337M − 21
FIG. 1 Schematic of Suitable Apparatus for Direct Single-Lap Shear Test
the LVDT (Fig. 2). A cut-through discontinuity of the hole is the Ω-shaped plate should be between 1 mm [0.04 in.] and 2
used to accommodate LVDTs of different sizes. An additional mm [0.08 in.]. The other recommended dimensions c, c , and
threadedholeisusedtoinsertascrewtotightentheLVDT.The c of the Ω-shaped plate are provided in Appendix X1 and are
holder can be glued to the surface of the concrete prism. Fig.
basedontherecommendeddimensionsofthespecimenshown
2showsadditionaldetailsoftheportionofthetestsetupwhere
in Fig. X1.1.
theLVDTsaremounted.Therecommendeddistance vbetween
7.7 Optional Out-of-Plane Displacement Measurement—
the axis of the LVDT and the edge of the composite strip
Two optional LVDTs (named LVDT C and D in Fig. 1) can be
should be equal to 20mm [0.8in.].The LVDTs (named LVDT
used to monitor the out-of-plane displacement of the concrete
AandBin Fig. 1) react off of a thin aluminum Ω-shaped plate
prism, that is, the displacement in the direction perpendicular
thatshouldbeattachedtothecompositesurfaceadjacenttothe
tothefaceofthecompositestrip.TwoLVDTholdersshouldbe
beginning of the bonded area. The epoxy used for the FRP
mounted onto the bottom plate using two magnets. The LVDT
system should be used to apply the Ω-shaped plate to the
C and D react off of the face of concrete prism parallel to the
surface of the FRP composite. As shown in Fig. 2, epoxy is
one to which the composite is applied. The distance z of the
used to create two weld bead-like strips that firmly attach the 1
measurement point should be provided in the report. The
Ω-shapedplatetotheFRPstrip.Thebottomepoxystripshould
distance on center z between LVDT C and LVDT D should be
not overlap with the bonded area. The flanges of the Ω-shaped
plateoverhangfromtheFRPstrip.Therefore,cardboardcanbe 80mm[3in.]ifthedimensionsoftheprismprovidedin8.3are
used. The use of LVDT C and D, although optional, is highly
used as a temporary support of the aluminum plate until the
epoxy used to attach the plate itself is cured. The thickness of recommended to monitor the out-of-plane displacement.
D8337/D8337M − 21
FIG. 2 Details of theΩ-Shaped Plate
7.8 Optional Strain Measurements on the FRP Surface— 8. Sampling and Test Specimen
Strain gages could be applied along the centerline of the FRP
8.1 Dimensional Tolerances—Dimensional tolerances de-
strip (that is, along the direction of the fibers) to obtain the
scribed in 7.2 are applied to the concrete prism and FRP strip
profile(s) of the longitudinal strain component ɛ (reference
yy
dimensions.
systeminFig.1)correspondingtoone(ormore)point(s)ofthe
8.2 Sampling—Test at least five specimens per test condi-
load response within the interval of global slip (g , g ) defined
1 2
tionunlessvalidresultscanbegainedthroughtheuseoffewer
in 11.8. An active gage length of 6mm [0.25in.] is recom-
specimens, such as in the case of a designed experiment. For
mended for most materials.Active gage lengths should not be
statisticallysignificantdata,theproceduresoutlinedinPractice
less than 3mm [0.125in.]. Gage calibration certification shall
E122 should be consulted. The method of sampling shall be
comply with Test Methods E251. It is recommended that at
reported.
least 6 strain gages are applied along the bonded length to
obtain a reliable strain profile. It is recommended that, if
8.3 The concrete test specimen shall conform to all require-
available, digital image correlation (DIC) is used instead of
ments of Test Method C42/C42M or Practices C31/C31M or
strain gages to obtain the strain profile(s) along the centerline
C192/C192M. The recommended dimensions of the concrete
of the FRPstrip. For each value of y (reference system in Fig.
prismare b=150mm[6in.]width× d=150mm[6in.]depth
1), the longitudinal strain component ɛ should be averaged
× L=450mm[18in.]length(Fig.3).Dimensions b, d, Lofthe
yy
over a strip centered with respect to the width of the FRPstrip
prismcanbevariedaslongastheyarekeptconstantwithinthe
and corresponding to the interval -5 mm [-0.2in.] ≤ x ≤5mm
same experimental protocol. Dimensions b and d could be
[0.2in].
varied independently (as long as constant for the same experi-
mental protocol) since rectangular cross-sections of the con-
NOTE 1— If the overall width of the FRP strip is smaller than 20mm
crete prism are allowed. The sides of the specimen shall be at
[0.8in.],theintervalof xtoaveragethevaluesofthestraincomponent ɛ
yy
obtained from DIC should be equal to half of the width of the FRP strip. right angles with the top and bottom. All surfaces, except for
D8337/D8337M − 21
FIG. 3 Specimen Dimensions and Details of Bonded FRP System
the troweled face, shall be smooth and free of scars, 8.5 Surface preparation of the specimen face that will
indentations, holes, or inscribed identification marks. receive the FRP system shall be in accordance with the FRP
manufacturer’s requirements of the FRP system being tested.
8.4 Cast Specimens (Practices C31/C31M or C192/
Details of the surface preparation shall be recorded with the
C192M)—Cast specimen concrete mixture shall meet the
test data.
following requirements:
8.5.1 The bond break d, that is, the distance between the
f
8.4.1 Aggregates—Aggregates shall conform to Specifica-
beginning of the bonded area and the top edge (at loaded end
tion C33/C33M, and the maximum aggregate size should be
3 5 ofthecompositestrip)oftheconcreteprism(Fig.1),shouldbe
10mm[ ⁄8in.] or 15mm [ ⁄8in.], unless the effect of the
70mm [2.75in.] minimum to avoid spalling of concrete.
aggregate size on the bond capacity is an objective of a test
program.
NOTE2—Bondbreakingiseasilyaccomplishedusingmaskingtapethat
8.4.2 Cement—UseTypeI/IIportlandcementconformingto
covers the concrete surface from the top edge to the beginning of the
bonded area. For additional details, refer to 8.6.4 and Fig. 4.
Specification C150/C150M. The concrete mixture shall not
includeanyothercementitiousmaterials(forexample,slag,fly
8.6 The FRP system applied to one face of the specimen
ash, silica fume, or limestone powder) or chemical admixtures
should meet the following requirements as shown in Fig. 3:
(for example, air-entraining agents, water reducers, high-range
8.6.1 The FRP system shall be applied in accordance with
water reducers, shrinkage-compensating admixtures, corrosion
the FRP manufacturer’s recommended procedure. The FRP
inhibitors, set retarders, and set accelerators) unless the evalu-
manufacturer’s instructions should be followed as to the
ation of these is an objective of the test program.
elapsed time between FRP system application and testing.
8.4.3 Concrete Strength—Cylinders should be cast and
8.6.2 The width of the applied FRPsystem should be equal
tested in accordance with Practice C31/C31M, Test Method
to 50mm [2in.] if the width of the concrete prism is 150mm
C39/C39M, Test Method C496/C496M, and Practice C617/
[6in.]. The FRP system shall be centered on the strengthened
C617M. The 28-day compressive strength fˊ of the cylinders
c
face of the prism. A different width of the composite strip is
should fall between 22 to 55MPa [3200 to 8000psi]. The
allowed.
28-day splitting tensile strength fˊ should fall between 2 MPa
t
8.6.3 Thebondedlength ℓ oftheappliedFRPsystemshould
[300 psi] and 10MPa [1500psi]. The ranges provided for fˊ
c
be equal to 300mm [12in.]. A different bonded length of the
and fˊ do not need to be considered if the test is used to
t
composite strip is allowed.
determine the effect of mechanical properties of concrete on
the bond capacity of the FRP composite strip. 8.6.4 The composite strip will be longer than the bonded
8.4.4 Curing—Cure cylinders and concrete specimens for length ℓ. If a wet layup procedure is used (Test Method
28 days in water in accordance with Specification C511. D7565/D7565M),asupportfortheFRPstrip,whichoverhangs
D8337/D8337M − 21
FIG. 4 Details of the Supporting Block Used to Apply the FRP Strip
from the concrete prism (Fig. 4), should be provided in order environmental exposure (for example: alkaline solution, etc.).
to cast the composite with all the fibers parallel to the concrete In such cases, test specimens should be conditioned as speci-
surface. Tape and plastic sheet can be used to mask the fied in the experimental protocol.
remaining surface of concrete in order to avoid resin bonding
10.2 If not otherwise specified, the recommended pre-test
to concrete outside the bonded area (Fig. 4).
condition for control or other specimens not otherwise subject
8.6.4.1 The total length L (Fig. 1 and Fig. 3) of the FRP toenvironmentalconditioningiseffectivemoistureequilibrium
f
compositeshouldbecomputedinaccordancewithEq1andEq at a specific relative humidity as established by Test Method
2: D5229/D5229M; however, if the test requestor does not
explicitly specify a pre-test conditioning environment, no
L 5 ℓ1d 1300 mm (1)
f f
conditioning is required and the specimens may be tested as
L 5 ℓ 1 d 1 12 in. (2)
@ #
f f
prepared.
NOTE 5—The term moisture, as used in Test Method D5229/D5229M,
NOTE 3—The total length L can be reduced if the testing machine
includes not only the vapor of a liquid and its condensate, bu
...