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1.1 This test method covers procedures for evaluating the pull-off strength of a coating on concrete. Pull-Off strength of coatings for other rigid substrates is described in Test Method D4541. The test determines the greatest perpendicular force (in tension) that a surface area can bear before a plug of material is detached. Failure will occur along the weakest plane within the system comprised of the loading fixture, glue, coating system, and substrate, and will be exposed by the fracture surface.

1.2 This test method uses a class of apparatus known as portable pull-off adhesion testers.2 They are capable of applying a concentric load and counter load to a single surface so that coatings can be tested even though only one side is accessible. Measurements are limited by the strength of adhesion bonds between the loading fixture, coating system and the substrate or the cohesive strengths of the glue, coating layers, and substrate.

1.3 This test method is suitable for both laboratory and field testing.

1.4 Pull-off strength measurements depend upon both material and instrumental parameters. There are different instruments used that comply with this test method. The specific instrument used should be identified when reporting results. This test is destructive and spot repairs may be necessary.

1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.6 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.

1.7 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.

5.1 The pull-off strength and mode of failure of a coating from a concrete substrate are important performance properties that are used in specifications. This test method serves as a means for uniformly preparing and testing coated surfaces, and evaluating and reporting the results.

5.2 Variations in strength results obtained using different instruments, different substrates, or different loading fixtures with the same coating are possible. Therefore, it is recommended that the specific test instrument and loading fixture be mutually agreed upon between the interested parties.

5.3 It is recommended that the coating be sufficiently cured to ensure cohesive strength and adhesion. This required minimum cure time before testing should be provided by the coating manufacturer, and may require an extension due to atmospheric conditions on site (for example, low temperature, and low or high humidity).

5.4 This test method may be adapted to determine surface strength of uncoated concrete (see X2.1). Test Method C1583 is also suitable for that determination.

5.5 The objective of this method is to determine the adhesion of a coating to concrete (or adapted for surface strength as stated in 5.4) and will result in failure in the coating or near the substrate surface. If evaluating the cohesive strength of the substrate or cementitious surfacers is the purpose of the testing, or if the substrate or cementitious surfacers have low strength, then Test Method C1583 may be more suitable.