1、Designation: D7522/D7522M 09D7522/D7522M 15Standard Test Method forPull-Off Strength for FRP Laminate Systems Bonded toConcrete Substrate1This standard is issued under the fixed designation D7522/D7522M; the number immediately following the designation indicates theyear of original adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the apparatus and procedure for evaluating the pull-off st
3、rength of wet lay-up or pultruded(shop-fabricated) Fiber Reinforced Polymer (FRP) laminate systems adhesively bonded to a flat concrete substrate. The testdetermines the greatest perpendicular force (in tension) that an FRP system can bear before a plug of material is detached. Failurewill occur alo
4、ng the weakest plane within the system comprised of the test fixture, FRP laminate, adhesive and substrate.1.2 This test method is primarily used for quality control and assessment of field repairs of structures using adhesive-appliedcomposite materials.1.3 This test method is appropriate for use wi
5、th FRP systems having any fiber orientation or combination of ply orientationscomprising the FRP laminate.1.4 This test method is not appropriate for use as an “acceptance” or “proof” wherein the FRP system remaining intact at aprescribed force is an acceptable result.1.5 Pull-off strength measureme
6、nts depend upon both material and instrumental parameters. Different adhesion test devices andprocedures will give different results and cannot be directly compared.1.6 This test method can be destructive. Spot repairs may be necessary. The test method will result in an exposed cut FRPsection; repai
7、r methods must consider the potential for moisture uptake through this cut section.1.7 Prior to the installation of some adhesively bonded FRP systems, the substrate concrete must be patched (often to replacelost concrete volume). This test method is not appropriate for determining the pull-off stre
8、ngth of the FRP from the patch material.An additional test method is required to determine the pull-off strength of the patch from the substrate concrete. Throughout thisstandard, “substrate” is understood to mean the concrete or concrete patch material to which the FRP is adhered.1.8 The values sta
9、ted in either SI units or inch-pound units are to be regarded as standard. Within the text, the inch-pound unitsare shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be usedindependently of the other. Combining values from the two systems may
10、result in nonconformance with the standard.1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulator
11、ylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C125 Terminology Relating to Concrete and Concrete AggregatesD883 Terminology Relating to PlasticsD3878 Terminology for Composite MaterialsD5229/D5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of
12、Polymer Matrix CompositeMaterialsE6 Terminology Relating to Methods of Mechanical Testing1 This test method is under the jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of Subcommittee D30.10 on Compositesfor Civil Structures.Current edition approved June 1
13、, 2009April 15, 2015. Published July 2009May 2015. Originally approved in 2009. Last previous edition approved in 2009 asD7522/D7522M-09. DOI: 10.1520/D7522_D7522M-09.10.1520/D7522_D7522M-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at servi
14、ceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.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. B
15、ecauseit 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 versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 10
16、0 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E122 Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lot orProcess3. Terminology3.1 DefinitionsTerminology D3878 defines terms relating to high-modulus
17、fibers and their composites. Terminology D883defines terms relating to plastics. Terminology E6 defines terms relating to mechanical testing. Terminology C125 defines termsrelating to concrete. In the event of a conflict between terms, Terminology D3878 shall have precedence over the other standards
18、.3.2 Symbols:3.2.1 Ddiameter of the loading fixture.3.2.2 Fppull-off force.3.2.3 ppull-off bond stress.4. Summary of Test Method4.1 The pull-off test is performed by securing a circular loading fixture (dolly) normal (perpendicular) to the flat surface of theFRP laminate with an affixing adhesive. A
19、n adhesion testing device is attached to the loading fixture and aligned to apply tensionnormal to the test surface. The force applied to the loading fixture is gradually increased and monitored until a plug of materialis detached exposing the plane of limiting strength within the system. The nature
20、 of the failure is qualified in accordance with thepercent of adhesive and cohesive failures, and the actual interfaces and layers involved. The pull-off strength is computed basedon the maximum indicated force, the instrument calibration data, and the original surface area stressed. Pull-off streng
21、th resultsusing different devices may vary, as results are sensitive to test device parameters.5. Significance and Use5.1 The pull-off strength of a bonded FRP system is an important performance property that has been used in specifications,particularly those for assessing the quality of an applicat
22、ion. This test method serves as a means for uniformly preparing and testingbonded FRP systems, and evaluating and reporting the results.5.2 Variations in results obtained using different devices are possible. Therefore, it is recommended that the type of adhesiontest device (including manufacturer a
23、nd model) be mutually agreed upon between the interested parties.5.3 This test method is intended for use in both the field and the laboratory.5.4 The basic material properties obtained from this test method can be used in the control of the quality of adhesives and inthe theoretical equations for d
24、esigning FRP systems for external reinforcement to strengthen existing structures.6. Interferences6.1 Material and Specimen PreparationImproper preparation of the surface of the composite material before bonding thecircular loading fixture is known to cause premature failures at this interface. Impr
25、oper curing of the bonding adhesive can alsocause failure at this interface. Non-uniform FRP or FRP-to-substrate adhesive thickness in one specimen can affect an individualtest result and lead to non-symmetric or mixed-mode failure pattern. Variation in FRP or adhesive thickness between specimenscan
26、 cause biased or scattered test results. Improper fixturing of the hole cutter relative to the specimen can lead to a non-circularhole or damage to the FRP composite/substrate interface around the perimeter of the hole. This can cause biased or scattered testresults and non-symmetric or mixed-mode f
27、ailure patterns. Misalignment between the circular test fixture and the drilled circle canalso lead to biased or scattered test results and noo-symmetricnon-symmetric or mixed-mode failure patterns.6.2 Adhesion Testing DeviceImproper alignment of the adhesion tester grip (see 7.1.3) can lead to bias
28、ed or scattered testresults and non-symmetric or mixed-mode failure patterns. Variation in the rate of loading between specimens can cause biasedor scattered test results.6.3 Environmental Conditions at Time of TestingTesting at non-standard temperaturestemperature or relative humiditieshu-midity ma
29、y affect the test results. Specimens tested in field conditions should be noted as such.7. Apparatus7.1 Fixed Alignment Adhesion Test Device, commercially available, or comparable apparatus conforming to the followingspecifications. A specific example of an appropriate commercially available tester
30、is provided in Annex A1.7.1.1 The tester is comprised of detachable circular loading fixtures, screws with spherical heads that are screwed into the centerof a fixture, a socket in the testing assembly that holds the head of the screw, pressure gage or dynamometer, and a mechanicalor hydraulic means
31、 of applying the force in a controlled manner.7.1.2 Loading Fixtures, having a minimum diameter of 50 mm 2.0 in., a flat surface on one end that can be adhered to theFRP surface and a means of attachment to the tester on the other end.7.1.3 Adhesion Tester Grip, having a central grip for engaging th
32、e loading fixture in a manner such that the resultant force isnormal to the FRP surface (typically achieved with a spherical head bearing).D7522/D7522M 1527.1.4 Adhesion Tester Base, permitting a uniform bearing against the FRP surface to react the test force.7.1.5 Means of moving the grip away from
33、 the base in as smooth and continuous a manner as possible so that a torsion-free,co-axial (opposing pull of the grip and push of the base along the same axis) force results between them.7.1.6 Timer, or means of limiting the rate of stress applied to the FRP-concrete interface being tested to less t
34、han or equal to1 MPa/min. 150 psi/min. A timer is the minimum equipment when used by the operator along with the force indicator in 7.1.7.7.1.7 Force Indicator and Calibration Information, for determining the actual force delivered to the loading fixture.7.2 Loading Fixture Bonding Adhesive, for sec
35、uring the fixture to the FRP laminate such that laminate properties are notaffected. The bonding adhesive must have a tensile capacity greater than the expected tensile capacity of the FRP system and theconcrete substrate and be sufficient to mitigate a Failure Mode A (see 12.2.1). Two component epo
36、xies have been found to beappropriate.7.3 Circular Hole Cutter, having an inside diameter equal to that of the loading fixture to score through the FRP laminate intothe substrate around the loading fixture. The hole cutter must not damage the FRP laminate while scoring through it; therefore athin-wa
37、lled diamond grit hole saw is appropriate. In most cases a center drill arbor may be used to facilitate the scoring operationwithout affecting test results.8. Test Specimen Preparation and Sampling8.1 The FRP system is applied to the concrete surface in accordance with the manufacturers recommended
38、procedure. Themanufacturers instructions should be followed as to the elapsed time between FRP application and pull-off testing.8.2 SamplingTest at least five specimens per test condition unless valid results can be gained through the use of fewerspecimens, such as in the case of a designed experime
39、nt. For statistically significant data, the procedures outlined in Practice E122should be consulted. The method of sampling shall be reported.9. Calibration9.1 The accuracy of all measuring equipment shall have certified calibrations that are current at the time of use of the equipment.10. Condition
40、ing10.1 This testing may be completed to assess a variety of effects including concrete surface preparation, adhesive curingconditions, hygrothermal exposure, environmental exposure (for example, alkaline solution, etc.). In such cases, test specimensshould be conditioned as specified in the experim
41、ental protocol.10.2 If not otherwise specified, the recommended pre-test condition is effective moisture equilibrium at a specific relativehumidity as established by Test Method D5229/D5229M; however, if the test requestor does not explicitly specify a pre-testconditioning environment, no conditioni
42、ng is required and the specimens may be tested as prepared.10.3 If pre-conditioning is completed, the pre-test specimen conditioning process, to include specified environmental exposurelevels shall be reported with the test data.10.4 If no explicit conditioning process is performed the specimen cond
43、itioning process shall be reported as unconditioned andthe moisture content as unknown.NOTE 1The term moisture, as used in Test Method D5229/D5229M, includes not only the vapor of a liquid and its condensate, but the liquid itselfin large quantities, as for immersion.11. Procedure11.1 Select a flat
44、measurement site in accordance with the sampling schedule.11.2 Select a circular loading fixture having a diameter not less than 50 mm 2.0 in. For FRP bonded to concrete substrateswhich are known to contain large aggregate sizes, a larger fixture may be usedused.NOTE 2The loading fixture diameter is
45、 limited by the test device dimensions and capacity. Little data is available for diameters greater than 50 mmregardless of aggregate size; generally a 50 mm diameter test fixture will be adequate.11.3 Score through the FRP laminate into the substrate concrete using a core drill apparatus. The remai
46、ning scribed circle (thatis, the inside diameter of the core drill) should be the same diameter as the loading fixture used. The core shall be drilled throughthe bonded FRP and adhesive layers and into the concrete substrate a depth of between 6 mm 0.25 in. and 12 mm 0.50 in.11.3.1 The operator must
47、 be aware of existing internal reinforcement (“rebar”). Under no circumstances should the drilled corecut through existing reinforcement.11.4 Prepare the FRPsurface for bonding the loading fixture. Generally, the FRPsurface should be cleaned with solvent, sandedwith medium-grit sandpaper, rinsed wit
48、h solvent, and allowed to dry.NOTE 3Generally, any surface preparation of the FRPthat results in test fixture adhesion sufficient to avoid occurrence of Failure ModeA(see 12.2.1)is adequate.11.5 Attach the loading fixture with the designated bonding adhesive following the manufacturers instructions.
49、 The bondingadhesive must be permitted to cure sufficiently so that Failure Mode A (see 12.2.1) does not occur.D7522/D7522M 15311.6 Carefully connect the central grip of the adhesion tester to the loading fixture without bumping, bending, or otherwisestressing the sample and connect the assembly to its control mechanism. For non-horizontal surfaces, support the adhesion testerassembly so that its weight does not contribute to the force exerted in the test.11.7 Align the device according to the manufacturers instructions and set the force indicator to z
