Freeze-thaw cycling under a calcium chloride environment: effects on CFRP strengthened concrete structures: Fid-Bau Portal

Freeze-thaw cycling under a calcium chloride environment: effects on CFRP strengthened concrete structures

Boyajian, David M. / Ray, Indrajit / Davalos, Julio F.

The fracture mechanics specimen known as the Single Contoured-Cantilever Beam (SCCB) - an experimental approach designed to ascertain both qualitative and quantitative information about the integrity of Fibre Reinforced Polymer (FRP) laminate-to-concrete interface bonds - has been used to assess the detrimental effects of subjecting concrete structures externally strengthened with Carbon Fibre Reinforced Polymer (CFRP) sheets to a combined thermo-chemical environment involving Freeze-Thaw (FT) cycling under a calcium chloride (CaCl2) solution. Quantitative fracture measurements in terms of the Mode I critical strain energy release rates (Glc) were recorded after 50, 100, 150, 200 and 300 cycles of alternate freezing and thawing; moreover, specimen weights and strains were measured initially and at the end of every 5th cycle. Considerable degradation of the interface bond integrity was found to have resulted, particularly for the latter-stage cycled beams. From weight measurements along with visual observations, cycle 150 was found to be a pivotal point of demarcation between specimen-soundness and -degeneration. There was no appreciable development of strain at the concrete-CFRP interface throughout the duration of the FT aging protocol. The concrete-CFRP interface as subjected to freezing and thawing was found to render a characteristically strain rate insensitive phenomena, i.e. the crack propagation proceeded in a stable manner. After the complete duration of FT aging at 300 cycles, SCCB fracture testing revealed that the interface integrity had been compromised to a functional-level operating at less than two-thirds the efficiency as those resulting from the control