The CFRP-Concrete Interface Subjected to Sodium - Sulfate and -Hydroxide Attack

摘要

The recently developed experimental fracture approach known as the Single Contoured-Cantilever Beam (SCCB) specimen is implemented to evaluate environmentally conditioned concrete-FRP interfaces. Fracture studies are conducted on specimens that have undergone 10, 20 and 30 cycles of alternate wetting and drying (one cycle constitutes 3 days of wetting and 4 days of drying in an environmental chamber maintained at 40 C and 50% relative humidity). Half of the 24 conditioned specimens studied were placed in a 10% sodium sulfate solution (pH = 6.2 - 6.5) and half were soaked in sodium hydroxide (pH = 12) to simulate naturally occurring acidic and alkaline field exposure-conditions, respectively. At the end of each target age, SCCB fracture testing was conducted, both, on these weathered beams, as well as on a set of unconditioned companion specimens, thus enabling the acquisition of necessary baseline-feedback for making relative comparisons of corresponding critical strain energy release rate (G{sub}(Ic)) values. Two approaches are used in determining the fracture toughness of the CFRP-concrete interface bond, both of which depend on the proper identification of loads reaching a critical state, P{sub}c. In the first, the topmost, or "head", -initiation and -arrestment loads are averaged, and in the second, the mean of the entire "set" of -initiation and -arrestment loads is taken. This raw-data is then reduced by the employment of a statistical-based method from which a range of permissible critical loads is designated. The final G{sub}(Ic) values are obtained based on an average of this refined data. Considerable degradation of the CFRP-concrete interface bond integrity is found to have resulted, especially for cases of latter-stage cycling in the aggressive sodium -sulfate and -hydroxide media.