Effect of sulfates on bond behavior between carbon fiber reinforced polymer sheets and concrete

The bond–slip behavior between sulfate-damaged concrete and carbon fiber reinforced polymer-sheets was investigated using double shear pull-off concrete specimens. Concrete blocks (150 × 150 × 100 mm) were subjected to two different levels of sulfate cyclic treatment before and after bonded to carbon fiber reinforced polymer (CFRP) sheets. Other sets of concrete specimens bonded and unbounded to CFRP were maintained in lime water as controls. CFRP were attached to concrete at three different CFRP bonded widths (bf) of (50, 100 and 150 mm) and two CFRP bonded lengths (Lf) of (65 and 85 mm). Present and literature data were employed in the development of a statistical model to estimate the ultimate shear strength and slippage between CFRP sheets and sulfate-damaged concrete. The results showed reductions in the bond stress and corresponding slippage with further cyclic sulfate treatment, with specimens bonded to CFRP before showing better bond behaviors than those of specimens bonded to CFRP after sulfate treatment. The ultimate normal stress in CFRP sheets decreased with further sulfate treatment. The statistical model developed showed excellent fit of the data used and collected as indicated by the high R2 (coefficients of determination) values.