Experimental investigation into bond behavior of FRP-to-concrete under mixed-mode I/II loading

•Bond behavior of CFRP-to-concrete joints under mixed-mode I/II loading was experimentally investigated.•A non-contact digital image correlation system was used to obtain the load-slip responses of the joints.•Interaction of axial force and the out-of-plane normal force was derived from experiments.•A simple model was proposed to predict FRP-to-concrete bond strength under mixed-mode I/II loading.