Prediction of Degradation of Interface Fracture Energy from Accelerated Aging Tests and Mode-II Loading

Rehabilitating and retrofitting concrete structural members using externally bonded Fiber Reinforced Polymer (FRP) strips has been gaining steadily use in recent years because of its many advantages. An important design issue with significant performance and safety implications is the debonding of externally bonded FRP strips in flexural members, where the delamination is primarily due to Mode-II facture. Although extensive research has been conducted on Mode II fracture of CFRP-concrete interface, only limited studies are available on durability. This paper explores the long-term behavior of FRP-concrete interface under Mode II loading condition through a combined accelerated ageing test and a prediction model based on Arrhenius relation. Mode-II single shear test was adopted in the accelerated ageing test, where specimens were subjected simultaneously to two environmental conditioning effects: (1) immersed in deionized water varying from 0 to 13 weeks; and (2) controlled temperatures varying from 25°C to 60°C (77°F to 140°F) of samples while immersed in water. The Energy Release Rate (ERR) determined before and after conditioning was considered a measure of the durability performance of the specimens. Based on the short-term data from the accelerated aging test, a detailed procedure is developed using Arrhenius relation to predict the long-term performance of the CFRP-concrete interface. It can be concluded that the accelerated ageing test and the prediction procedure used in this study can be a useful tool to evaluate the durability of the CFRP-concrete interface.