Evaluation of Procedures for In Situ Tensile Bond Testing of Concrete Repairs

To achieve durable repairs, it is usually necessary to ensure adequate bond between the repair and the existing concrete substrate. Tensile bond tests are being increasingly used for quality control/quality assurance testing. However, there has been little standardization of test methods. Consequently, a total of 266 partial-depth cores in 77 experimental repairs were tested to evaluate the effect of material properties and environmental conditions on the bond between nine repair materials and a common concrete substrate. Three pull-off testing devices were used to determine bond strengths for each of the experimental repairs. In addition, the testing devices themselves were evaluated by analyzing the magnitude and relative precision of the pull-off strengths, modes of failure, and ease of use in an effort to identify a reliable and practical device for determining in situ tensile bond. The optimum depth of core drilling into the existing substrate was determined by comparing theoretical finite element analyses of failure stress and location with measured test results.