1、Designation: D 7234 05Standard Test Method forPull-Off Adhesion Strength of Coatings on Concrete UsingPortable Pull-Off Adhesion Testers1This standard is issued under the fixed designation D 7234; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for evaluating thepull-off adhesion strength of a coatin
3、g on concrete. The testdetermines the greatest perpendicular force (in tension) that asurface area can bear before a plug of material is detached.Failure will occur along the weakest plane within the systemcomprised of the test fixture, adhesive, coating system, andsubstrate, and will be exposed by
4、the fracture surface.1.2 This test method uses a class of apparatus known asportable pull-off adhesion testers.2They are capable of apply-ing a concentric load and counter load to a single surface sothat coatings can be tested even though only one side isaccessible. Measurements are limited by the s
5、trength of adhe-sion bonds between the loading fixture, coating system and thesubstrate or the cohesive strengths of the adhesive, coatinglayers, and substrate.1.3 Pull-off adhesion strength measurements depend uponboth material and instrumental parameters. There are differentinstruments used that c
6、omply with this test method. Thespecific instrument used should be identified when reportingresults. This test is destructive and spot repairs may benecessary.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 This standar
7、d 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. Referenced Documents2.1 ASTM
8、 Standards:3C 1583/C 1583M Test Method for Tensile Strength of Con-crete Surfaces and the Bond Strength or Tensile Strength ofConcrete Repair and Overlay Materials by Direct Tension(Pull-off Method)D16 Terminology for Paint, Related Coatings, Materials,and ApplicationsD 2651 Guide for Preparation of
9、 Metal Surfaces for Adhe-sive BondingD 3933 Guide for Preparation of Aluminum Surfaces forStructural Adhesives Bonding (Phosphoric Acid Anodiz-ing)D 4541 Test Method for Pull-Off Strength of CoatingsUsing Portable Adhesion TestersE 178 Practice for Dealing With Outlying Observations3. Terminology3.1
10、 The terms and definitions in Terminology D16apply tothis test method.3.2 Definitions:3.2.1 adhesive, n(with respect to this test method) adhe-sive refers to the material that bonds the bottom of the loadingfixture to the top surface of the coating to be tested.3.2.2 loading fixture, n(also referred
11、 to as dollies or studs)a metal structure that is flat on one end for bonding to thecoating surface and shaped on the other end for attachment tothe adhesion tester and is used to determine the pull-offadhesion strength of coatings3.2.3 portable pull-off adhesion testers, ninstruments thatare capabl
12、e of applying a concentric load and counter load toa single surface so that coatings can be tested even though onlyone side is accessible.4. Summary of Test Method4.1 The general pull-off adhesion test is performed byscoring through the coating down to the surface of the concretesubstrate at a diame
13、ter equal to the diameter of the loadingfixture (dolly, stud), and securing the loading fixture normal(perpendicular) to the surface of the coating with an adhesive.After the adhesive is cured, a testing apparatus is attached tothe loading fixture and aligned to apply tension normal to thetest surfa
14、ce. The force applied to the loading fixture is thenuniformly increased and monitored until a plug of material isdetached. When a plug of material is detached, the exposed1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and i
15、s the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved Dec. 1, 2005. Published February 2006.2The term adhesion tester may be somewhat of a misnomer, but its adoption bytwo manufacturers and at least two patents indicates continued usage.3For ref
16、erenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, We
17、st Conshohocken, PA 19428-2959, United States.surface represents the plane of limiting strength within thesystem. The nature of the failure is qualified in accordance withthe percent of adhesive and cohesive failures, and the actualinterfaces and layers involved. The pull-off adhesion strength iscom
18、puted based on the maximum indicated load, the instru-ment calibration data, and the surface area stressed. Pull-offadhesion strength results obtained using different devices maybe different because the results depend on instrumental param-eters.5. Significance and Use5.1 The pull-off adhesion stren
19、gth and mode of failure of acoating from a concrete substrate are important performanceproperties that are used in specifications. This test methodserves as a means for uniformly preparing and testing coatedsurfaces, and evaluating and reporting the results.5.2 Variations in strength results obtaine
20、d using differentinstruments, different substrates, or different loading fixtureswith the same coating are possible. Therefore, it is recom-mended that the specific test instrument and loading fixture bemutually agreed upon between the interested parties.5.3 This test method should not be used to de
21、terminesurface strength of uncoated concrete. Test Method C 1583/C 1583M is suitable for that determination.6. Apparatus6.1 Adhesion Tester, including the components and acces-sories described in 6.1.1-6.1.56.1.1 Loading Fixtures, having a flat surface on one end thatcan be adhered to the coating an
22、d a means of attachment to thetester on the other end. The bonding surface may be round,square or rectangular. The round loading fixtures are usually 50mm (2.0 in) in diameter but may range from 20 mm (0.75 in)to 75 mm (3.0 in) in diameter.6.1.2 Detaching Assembly, having a central grip for engag-in
23、g the loading fixture.6.1.3 Base, on the detaching assembly, for uniformly press-ing against the coating surface around the fixture eitherdirectly, or by way of an intermediate bearing ring. A means ofaligning the base is needed so that the resultant force is normalto the surface.6.1.4 Force Applica
24、tor, means of moving the grip awayfrom the base in as smooth and continuous a manner aspossible so that a torsion free, co-axial (opposing pull of thegrip and push of the base along the same axis) force resultsbetween them.6.1.5 Force Indicator and Calibration Information, fordetermining the actual
25、force delivered to the loading fixture.The force indicator shall be verified to be within +/-5 % of theforce measured by a calibrated testing machine at a frequencydetermined by the user, typically once a year.6.2 Timer, or means of limiting the rate of stress to less than0.2 MPa/s (30 psi/s) so tha
26、t the maximum stress (failure) isobtained in about 5 to 30 s.6.3 Solvent, or other means for cleaning the loading fixturesurface.6.4 Fine Sandpaper, or other means of cleaning or prepar-ing the coating that will not alter its integrity.6.5 Adhesive, for securing the fixture to the coating that doesn
27、ot affect the coating properties. Two-component epoxies andacrylics4have been found to be the most versatile.6.6 Mechanical Clamps, if needed, for holding the fixture inplace while the adhesive cures.6.7 Cotton Swabs, or other means for removing excessadhesive.6.8 Core Bit with Drill Press or Hand D
28、rill, and means toensure that the scoring is normal to the coating for theprocedures that use a round loading fixture. The core bit insidediameter should equal the diameter of the loading fixture. If acore bit with an inside diameter equal to the diameter of theloading fixture is not available, the
29、closest size available shouldbe used. The core bit or saw blades should be diamond tippedand, when required to minimize heat and suppress dust,supplemented with water lubrication. For the test proceduresthat use a square or rectangular loading fixture, a circular sawis required instead of a core bit
30、 and drill. Alternately, for thinor elastomeric coatings, a sharp knife or hole saw may besufficient to score around the loading fixture.7. Test Preparation7.1 The method for selecting the coating sites to be preparedfor testing depends upon the objectives of the test andagreements between the contr
31、acting parties. There are, how-ever, a few physical restrictions imposed by the general methodand apparatus. The following requirements apply to all sites:7.1.1 The selected test area must be a flat surface largeenough to accommodate the specified number of replicate tests.The surface may have any o
32、rientation with reference togravitational pull. Each test site must be separated by at leastthe distance needed to accommodate the detaching apparatus.The size of a test site is essentially that of the secured loadingfixture. At least three replications are required in order tostatistically characte
33、rize the test area.7.1.2 The selected test areas must also have enough perpen-dicular and radial clearance to accommodate the apparatus, andbe flat enough to permit alignment. It should be noted thatmeasurements close to an edge may not be representative of thecoating as a whole.7.2 Scoring the coat
34、ing down to the surface of the substrateis required for all coatings thicker than 0.5 mm (20 mils) andfor all reinforced or elastomeric coatings. While scoring isrecommended for coatings thinner than 0.5 mm (20 mils), thetest may be performed without scoring, but the results shouldnote this exceptio
35、n. Scoring shall be performed in a mannerthat ensures the cut is made normal to the coating surface andin a manner that does not twist or torque the test area andminimizes heat generated and edge damage or microcracks tothe coating and the concrete substrate. For thick coatings it isrecommended to c
36、ool the coating and substrate during thecutting process with water lubrication. When using a round4The sole source of supply of the acrylics known to the committee at this timeis Versiloc 201 and 204 with accelerator, available from Lord Corp., IndustrialAdhesive Div., 2000 W. Grandview Blvd., P.O.
37、Box 10038, Erie, PA 16514. If youare aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.D7234052loading fixture, scoring is perfor
38、med before the loading fixtureis attached (see Fig. 1). When using square or rectangularloading fixtures, scoring is typically performed after theloading fixture is attached (see Fig. 2).7.3 Clean the surfaces in a manner that will not affectintegrity of the coating or leave a residue. Clean the loa
39、dingfixture surface as indicated by the apparatus manufacturer.Failures at the fixture-adhesive interface can often be avoidedby treating the fixture surfaces in accordance with an appro-priate ASTM standard practice for preparing metal surfaces foradhesive bonding. Fingerprints, moisture, and oxide
40、s tend to bethe primary contaminants.NOTE 1Guides D 2651 and D 3933 are typical of well-proven meth-ods for improving adhesive bond strengths to metal surfaces.7.4 Prepare the adhesive in accordance with the adhesivemanufacturers recommendations. Apply the adhesive to thefixture or the surface to be
41、 tested, or both, using a methodrecommended by the adhesive manufacturer. Be certain toapply the adhesive across the entire surface. Position fixture onthe surface to be tested centered directly over the scoredsection with the fixture outer sides lined up with the insidecircumference of the scored s
42、ection. Carefully remove theexcess adhesive from around the fixture. (WarningMovement, especially twisting, can cause tiny bubbles tocoalesce into large holidays that constitute stress discontinui-ties during testing.)NOTE 2Adding about 1 percent of #5 glass beads to the adhesiveassists in even alig
43、nment of the test fixture to the surface.7.5 Based on the adhesive manufacturers recommendationsand the anticipated environmental conditions, allow enoughtime for the adhesive to set up and reach the recommendedcure. During the adhesive set and early cure stage, a constantcontact pressure should be
44、maintained on the fixture. Mechani-cal clamping systems work well, but systems relying on tack,such as masking tape, should be used with care to ensure thatthey do not relax with time and allow air to intrude between thefixture and the test area.7.6 Note the temperature and relative humidity during
45、thetime of test.8. Test Procedure8.1 Select an adhesion-tester having a force calibrationspanning the range of expected values along with its compat-ible loading fixture. Mid-range measurements are usually thebest, but read the manufacturers operating instructions beforeproceeding.8.2 If a bearing r
46、ing or comparable device is to be used,place it concentrically around the loading fixture on the coatingsurface. If shims are required when a bearing ring is employed,place them between the tester base and bearing ring rather thanon the coating surface.8.3 Carefully connect the central grip of the d
47、etachingassembly to the loading fixture without bumping, bending, orotherwise prestressing the sample and connect the detachingassembly to its control mechanism, if necessary. For nonhori-zontal surfaces, support the detaching assembly so that itsweight does not contribute to the force exerted in th
48、e test.8.4 Align the device according to the manufacturers in-structions and set the force indicator to zero.NOTE 3Proper alignment is critical. If alignment is required, use theprocedure recommended by the manufacturer of the adhesion tester.8.5 Increase the load to the fixture in as smooth andcont
49、inuous a manner as possible, at a uniform rate of less thanFIG. 1 Scoring Around the Loading Fixture Prior to Attachment of the Fixture (Round Loading Fixtures)D72340530.2 MPa/s (30 psi/s) so that failure occurs or the maximumstress is reached before 30 s.8.6 Record the force attained at failure.8.7 When the plug of material is detached, label and storethe fixture for qualification of the failed surface in accordancewith 9.3.8.8 Report any departures from the procedure such aspossible misalignment, hesitations in the force application, etc.9. Calculation and Interpretation o
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