Application of Fiber Reinforced Polymer (FRP) for rehabilitation of existing concrete structures is well-known nowadays. Externally Bonded Reinforcement (EBR) method is usually used to apply FRP composites on the concrete surface. However, a premature debonding failure mode may occur prior to achieving the full capacity of the FRP. The newly developed Externally Bonded Reinforcement On Groove (EBROG) method was shown to extensively postpone the debonding failure mode.
In this paper, bond behavior of prestressed FRP to concrete was investigated. Concrete blocks were strengthened with EBR and EBROG methods using prestressed Carbon FRP (CFRP) strips. The prestressing force was gradually decreased until the CFRP strip was debonded from the concrete substrate. Through these prestress force-releasing tests, the bond resistances of prestressed FRP to concrete were measured. Experimental results showed that EBROG method increased the bond resistance twice the EBR method. This high increase is attributed to the failure mode of the specimens. While the debonded layer in EBR method was a few millimeters beneath the FRP strip, it was deep and wide in the concrete substrate for EBROG method.