Effects of Different Groove Classes Used in Externally Bonded Reinforcement on Grooves Joints on Carbon Fiber-Reinforced Polymer-to-Concrete Bond Behavior

Externally bonded reinforcement on grooves (EBROG) was introduced as an alternative to the conventional externally bonded reinforcement (EBR) to postpone or eliminate premature debonding of fiber-reinforced polymer (FRP) sheets off the concrete substrate. EBROG joints come in a variety of forms and types as a result of varying groove designs and configurations concerning their width, height, spacing, and direction. It was the objective of the current study to investigate the effects of different groove classes not only on the effective bond length of carbon FRP (CFRP) sheets but also on the CFRP-to-concrete bond behavior. Particle image velocimetry (PIV) results revealed that the effective bond length in the EBROG joints tested exhibited a significant increase of up to 250.8% relative to the EBR joints, as evidenced by the rise in the effective bond length from 59.7 to 150.8 mm depending on the groove class. Although both longitudinal and transverse groove directions were observed to yield rather identical bond strengths in the experimental EBROG joints, they followed different bond mechanisms; more specifically, longitudinal grooves transferred stresses deep in the concrete, and transverse ones propagated stresses along the length of the concrete substrate. Finally, the presently available models of effective bond length are compared and evaluated using the experimental EBR and EBROG joint specimens.