1、Designation: D 7522/D 7522M 09Standard Test Method forPull-Off Strength for FRP Bonded to Concrete Substrate1This standard is issued under the fixed designation D 7522/D 7522M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the ye
2、ar 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 procedurefor evaluating the pull-off strength of wet lay-up or pult
3、ruded(shop-fabricated) Fiber Reinforced Polymer (FRP) laminatesystems adhesively bonded to a flat concrete substrate. The testdetermines the greatest perpendicular force (in tension) that anFRP system can bear before a plug of material is detached.Failure will occur along the weakest plane within th
4、e systemcomprised of the test fixture, FRP laminate, adhesive andsubstrate.1.2 This test method is primarily used for quality controland assessment of field repairs of structures using adhesive-applied composite materials.1.3 This test method is appropriate for use with FRPsystems having any fiber o
5、rientation or combination of plyorientations comprising the FRP laminate.1.4 This test method is not appropriate for use as an“acceptance” or “proof” wherein the FRP system remainingintact at a prescribed force is an acceptable result.1.5 Pull-off strength measurements depend upon both ma-terial and
6、 instrumental parameters. Different adhesion testdevices and procedures will give different results and cannot bedirectly compared.1.6 This test method can be destructive. Spot repairs may benecessary. The test method will result in an exposed cut FRPsection; repair methods must consider the potenti
7、al for mois-ture uptake through this cut section.1.7 Prior to the installation of some adhesively bonded FRPsystems, the substrate concrete must be patched (often toreplace lost concrete volume). This test method is not appro-priate for determining the pull-off strength of the FRP from thepatch mate
8、rial. An additional test method is required todetermine the pull-off strength of the patch from the substrateconcrete. Throughout this standard, “substrate” is understoodto mean the concrete or concrete patch material to which theFRP is adhered.1.8 The values stated in either SI units or inch-pound
9、unitsare to be regarded as standard. Within the text, the inch-poundunits are shown in brackets. The values stated in each systemare not exact equivalents; therefore, each system must be usedindependently of the other. Combining values from the twosystems may result in nonconformance with the standa
10、rd.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Reference
11、d Documents2.1 ASTM Standards:2C 125 Terminology Relating to Concrete and ConcreteAggregatesD 883 Terminology Relating to PlasticsD 3878 Terminology for Composite MaterialsD 5229/D 5229M Test Method for Moisture AbsorptionProperties and Equilibrium Conditioning of Polymer Ma-trix Composite Materials
12、E6 Terminology Relating to Methods of Mechanical Test-ingE 122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or Process3. Terminology3.1 DefinitionsTerminology D 3878 defines terms relatingto high-modulus fibers and their composit
13、es. TerminologyD 883 defines terms relating to plastics. Terminology E6defines terms relating to mechanical testing. TerminologyC 125 defines terms relating to concrete. In the event of aconflict between terms, Terminology D 3878 shall have prece-dence over the other standards.3.2 Symbols:3.2.1 Ddia
14、meter of the loading fixture.3.2.2 Fppull-off force.3.2.3 sppull-off bond stress.4. Summary of Test Method4.1 The pull-off test is performed by securing a circularloading fixture (dolly) normal (perpendicular) to the flat1This test method is under the jurisdiction of ASTM Committee D30 onComposite M
15、aterials and is the direct responsibility of Subcommittee D30.05 onStructural Test Methods.Current edition approved June 1, 2009. Published July 2009.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStand
16、ards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.surface of the FRP laminate with an affixing adhesive. Anadhesion testing device is attached to
17、the loading fixture andaligned to apply tension normal to the test surface. The forceapplied to the loading fixture is gradually increased andmonitored until a plug of material is detached exposing theplane of limiting strength within the system. The nature of thefailure is qualified in accordance w
18、ith the percent of adhesiveand cohesive failures, and the actual interfaces and layersinvolved. The pull-off strength is computed based on themaximum indicated force, the instrument calibration data, andthe original surface area stressed. Pull-off strength results usingdifferent devices may vary, as
19、 results are sensitive to test deviceparameters.5. Significance and Use5.1 The pull-off strength of a bonded FRP system is animportant performance property that has been used in specifi-cations, particularly those for assessing the quality of anapplication. This test method serves as a means for uni
20、formlypreparing and testing bonded FRP systems, and evaluating andreporting the results.5.2 Variations in results obtained using different devices arepossible. Therefore, it is recommended that the type of adhe-sion test device (including manufacturer and model) be mutu-ally agreed upon between the
21、interested parties.5.3 This test method is intended for use in both the field andthe laboratory.5.4 The basic material properties obtained from this testmethod can be used in the control of the quality of adhesivesand in the theoretical equations for designing FRP systems forexternal reinforcement t
22、o strengthen existing structures.6. Interferences6.1 Material and Specimen PreparationImproper prepa-ration of the surface of the composite material before bondingthe circular loading fixture is known to cause prematurefailures at this interface. Improper curing of the bondingadhesive can also cause
23、 failure at this interface. Non-uniformFRP or FRP-to-substrate adhesive thickness in one specimencan affect an individual test result and lead to non-symmetric ormixed-mode failure pattern. Variation in FRP or adhesivethickness between specimens can cause biased or scattered testresults. Improper fi
24、xturing of the hole cutter relative to thespecimen can lead to a non-circular hole or damage to the FRPcomposite/substrate interface around the perimeter of the hole.This can cause biased or scattered test results and non-symmetric or mixed-mode failure patterns. Misalignment be-tween the circular t
25、est fixture and the drilled circle can alsolead to biased or scattered test results and noo-symmetric ormixed-mode failure patterns.6.2 Adhesion Testing DeviceImproper alignment of theadhesion tester grip (see 7.1.3) can lead to biased or scatteredtest results and non-symmetric or mixed-mode failure
26、 patterns.Variation in the rate of loading between specimens can causebiased or scattered test results.6.3 Environmental Conditions at Time of TestingTestingat non-standard temperatures or relative humidities may affectthe test results. Specimens tested in field conditions should benoted as such.7.
27、Apparatus7.1 Fixed Alignment Adhesion Test Device, commerciallyavailable, or comparable apparatus conforming to the follow-ing specifications. A specific example of an appropriate com-mercially available tester is provided in Annex A1.7.1.1 The tester is comprised of detachable circular loadingfixtu
28、res, screws with spherical heads that are screwed into thecenter of a fixture, a socket in the testing assembly that holdsthe head of the screw, pressure gage or dynamometer, and amechanical or hydraulic means of applying the force in acontrolled manner.7.1.2 Loading Fixtures, having a minimum diame
29、ter of 50mm 2.0 in., a flat surface on one end that can be adhered tothe FRP surface and a means of attachment to the tester on theother end.7.1.3 Adhesion Tester Grip, having a central grip for engag-ing the loading fixture in a manner such that the resultant forceis normal to the FRP surface (typi
30、cally achieved with aspherical head bearing).7.1.4 Adhesion Tester Base, permitting a uniform bearingagainst the FRP surface to react the test force.7.1.5 Means of moving the grip away from the base in assmooth and continuous a manner as possible so that a torsion-free, co-axial (opposing pull of th
31、e grip and push of the basealong the same axis) force results between them.7.1.6 Timer, or means of limiting the rate of stress applied tothe FRP-concrete interface being tested to less than 1 MPa/min. 150 psi/min. A timer is the minimum equipment whenused by the operator along with the force indica
32、tor in 7.1.7.7.1.7 Force Indicator and Calibration Information, fordetermining the actual force delivered to the loading fixture.7.2 Loading Fixture Bonding Adhesive, for securing thefixture to the FRP laminate such that laminate properties arenot affected. The bonding adhesive must have a tensile c
33、apacitygreater than the expected tensile capacity of the FRP systemand the concrete substrate and be sufficient to mitigate a FailureMode A (see 12.2.1). Two component epoxies have been foundto be appropriate.7.3 Circular Hole Cutter, having an inside diameter equal tothat of the loading fixture to
34、score through the FRP laminateinto the substrate around the loading fixture. The hole cuttermust not damage the FRP laminate while scoring through it;therefore a thin-walled diamond grit hole saw is appropriate. Inmost cases a center drill arbor may be used to facilitate thescoring operation without
35、 affecting test results.8. Test Specimen Preparation and Sampling8.1 The FRP system is applied to the concrete surface inaccordance with the manufacturers recommended procedure.The manufacturers instructions should be followed as to theelapsed time between FRP application and pull-off testing.8.2 Sa
36、mplingTest at least five specimens per test condi-tion unless valid results can be gained through the use of fewerspecimens, such as in the case of a designed experiment. Forstatistically significant data, the procedures outlined in PracticeE 122 should be consulted. The method of sampling shall ber
37、eported.D 7522/D 7522M 0929. Calibration9.1 The accuracy of all measuring equipment shall havecertified calibrations that are current at the time of use of theequipment.10. Conditioning10.1 This testing may be completed to assess a variety ofeffects including concrete surface preparation, adhesive c
38、uringconditions, hygrothermal exposure, environmental exposure(for example, alkaline solution, etc.). In such cases, testspecimens should be conditioned as specified in the experi-mental protocol.10.2 If not otherwise specified, the recommended pre-testcondition is effective moisture equilibrium at
39、a specific relativehumidity as established by Test Method D 5229/D 5229M;however, if the test requestor does not explicitly specify apre-test conditioning environment, no conditioning is requiredand the specimens may be tested as prepared.10.3 If pre-conditioning is completed, the pre-test specimenc
40、onditioning process, to include specified environmental expo-sure levels shall be reported with the test data.10.4 If no explicit conditioning process is performed thespecimen conditioning process shall be reported as uncondi-tioned and the moisture content as unknown.NOTE 1The term moisture, as use
41、d in Test Method D 5229/D 5229M,includes not only the vapor of a liquid and its condensate, but the liquiditself in large quantities, as for immersion.11. Procedure11.1 Select a flat measurement site in accordance with thesampling schedule.11.2 Select a circular loading fixture having a diameter not
42、less than 50 mm 2.0 in. For FRP bonded to concretesubstrates which are known to contain large aggregate sizes, alarger fixture may be usedNOTE 2The loading fixture diameter is limited by the test devicedimensions and capacity. Little data is available for diameters greater than50 mm regardless of ag
43、gregate size; generally a 50 mm diameter testfixture will be adequate.11.3 Score through the FRP laminate into the substrateconcrete using a core drill apparatus. The remaining scribedcircle (that is, the inside diameter of the core drill) should bethe same diameter as the loading fixture used. The
44、core shall bedrilled through the bonded FRP and adhesive layers and intothe concrete substrate a depth of between 6 mm 0.25 in. and12 mm 0.50 in.11.3.1 The operator must be aware of existing internalreinforcement (“rebar”). Under no circumstances should thedrilled core cut through existing reinforce
45、ment.11.4 Prepare the FRP surface for bonding the loadingfixture. Generally, the FRP surface should be cleaned withsolvent, sanded with medium-grit sandpaper, rinsed with sol-vent, and allowed to dry.NOTE 3Generally, any surface preparation of the FRP that results intest fixture adhesion sufficient
46、to avoid occurrence of Failure Mode A (see12.2.1) is adequate.11.5 Attach the loading fixture with the designated bondingadhesive following the manufacturers instructions. The bond-ing adhesive must be permitted to cure sufficiently so thatFailure Mode A (see 12.2.1) does not occur.11.6 Carefully co
47、nnect the central grip of the adhesion testerto the loading fixture without bumping, bending, or otherwisestressing the sample and connect the assembly to its controlmechanism. For non-horizontal surfaces, support the adhesiontester assembly so that its weight does not contribute to theforce exerted
48、 in the test.11.7 Align the device according to the manufacturersinstructions and set the force indicator to zero.11.8 Apply manual or mechanized loading so that thecontinuous grip assembly motion results in a rate of appliednormal stress at the FRP-concrete interface of less than 1MPa/min. 150 psi/
49、min. until rupture occurs.11.9 Record pull-off force measurement and nature of fail-ure plane.11.10 If a plug of material is detached, label and store thetest specimen including the attached loading fixture for quali-fication of the failed surface in accordance with the experimentprotocol.11.11 Report any departures from the procedure such aspossible misalignment, hesitations in the force application, etc.12. Calculation and Interpretation of Results12.1 CalculationsCompute and record the pull-off bondstrength or concrete strength as follows:sp54FppD2(1)
