Effect of Variations in Practice of ASTM D7522 Standard Pull-Off Test for FRP-Concrete Interfaces

The recently promulgated ASTM D7522 Standard Test Method for Pull-Off Strength for FRP Bonded to Concrete Substrate provides a method for quality control and acceptance testing of fiber reinforced polymer (FRP) systems adhesively bonded to a concrete substrate. In the process of developing ASTM D7522, a number of comments and questions were received?some were incorporated as best practices and some were tabled, requiring further investigation. The present study addresses the latter issues and thereby directs future amendments of the ASTM D7522 standard method. Specifically, this study addresses the effects of specimen shape, the effects of variation in specimen cut depth, methods of cutting square specimens, and the impact of retesting specimens that do not fail during their initial test. It is shown that square specimens should be permitted although their results may not be directly compared with round specimens and they may have some other practical considerations affecting their use. Additionally, it is shown that cutting too deeply into the concrete substrate results in lower values of pull-off strength.