Bond Behavior between Basalt Fiber–Reinforced Polymer Sheet and Concrete Substrate under the Coupled Effects of Freeze-Thaw Cycling and Sustained Load

Abstract

This paper presents an experimental investigation on the bond behavior between basalt fiber–reinforced polymer (BFRP) sheet and concrete substrate under the coupled effects of freeze-thaw cycling and sustained load. Test variables were freeze-thaw cycles, level of sustained load, and adhesive type. Double-lap shear specimens were used in the tests, and a specially designed reaction-loading system was used to apply the sustained load during freeze-thaw cycles. Specimens with or without sustained load were exposed to up to 300 freeze-thaw cycles. A modified epoxy resin, made by adding a toughening agent to the original epoxy resin, was used in the test to study the effect of adhesive type on the durability of the BFRP–concrete interface. Coupon tests were also conducted to determine the freeze-thaw resistance of the constituent materials of the BFRP–concrete interface. After exposure, double-lap shear tests were carried out to investigate the residual bond capacity of the BFRP–concrete interface. Digital image correlation measurement was applied to capture the full-field deformation of the FRP sheet and the concrete block during the double-lap shear tests. A nonlinear bond-slip relationship of the BFRP–concrete interface was determined based on the analysis of displacement data. Test results show that (1) the bond capacity of the BFRP–concrete interface decreases with increasing freeze-thaw cycles, (2) the failure mode changes from debonding in the concrete layer to debonding in the adhesive layer, (3) extra degradation of the bond-slip relationship could be caused by the coupled effects, and (4) the durability improvement of the adhesive may result in a better durability of the BFRP–concrete bond capacity in a freeze-thaw environment. Finally, the coupled effects and evaluation of freeze-thaw procedures on the bond degradation of FRP–concrete interface are discussed.