Groove classification in EBROG FRP-to-concrete joints

This paper is a first attempt to classify the grooves concerning their depth, width, spacing, and direction to provide a variety of selections to be used in the ‘externally-bonded reinforcement on grooves’ (EBROG) method. Twelve classes of grooves were defined in both longitudinal and transverse directions. EBROG specimen joints with different classes of grooves were tested under a single lap-shear test to determine bond resistance, strain field, failure mode, and bond-slip behavior. Three failure modes of debonding, concrete crushing, and concrete cracking followed by debonding were observed in the EBROG joints with different groove classes. For constant groove dimensions, the ultimate load increased with decreasing groove spacing; e.g., for transverse grooves of 2.5 × 2.5 mm (width × height), an increase of about 75% was observed when the groove spacing decreased from 80 to 12 mm. Moreover, bond resistance in EBROG joints increased by up to 141% relative to that of the EBR joints when the groove class of 5 × 5 × 15 mm (width × height × spacing) was used in the transverse direction. Fracture energy was also determined for each groove class, and it was observed that the EBROG joint specimens with the groove class of 5 × 5 × 15 mm in the transverse direction exhibited fracture energies (2.25 N/mm) by more than five times greater than those of EBR joints (0.43 N/mm). The results obtained were exploited to formulate appropriate recommendations for the selection of optimum groove classes for each particular type of EBROG joint.