A Fracture Mechanics Approach for Interface Durability of Bonded FRP to Concrete

Synopsis: Externally bonded GFRP fabrics are being increasingly used for seismic retrofit and rehabilitation of concrete structures, due to their high strength to weight ratio and low cost in comparison to carbon and aramid fibers. However, glass fibers are vulnerable to attack caused by harsh environmental weathering conditions such as freezing-thawing, wetting-drying, and exposure to alkaline and acidic environments. Concerned with durability, this study is based on fracture mechanics to evaluate the interface durability of GFRP bonded to Normal Concrete (NC) and High-Performance Concrete (HPC). Three types of specimens are evaluated: (1) newly bonded unconditioned specimens, (2) environmentally conditioned specimens, and (3) correspondingly base-line companion specimens. Two types of environmental ageing protocols are defined: (1) freeze-thaw cycling under in calcium chloride, used to simulate the deleterious effect of the deicing salts; and (2) alternate wetting and drying in sodium-hydroxide, used to simulate the alkalinity due to the presence of concrete pore water. Durability of the interface is characterized based on the critical strain energy release rate, under Mode-I loading, and weight and strain measurements. Considerable degradation of the interface bond is observed with increasing environmental cycling period.