Mechanism of surface preparation on FRP-Concrete bond performance: A quantitative study

This paper quantitatively investigates the mechanism of surface preparation on the bond behavior of FRP-concrete interface. Two factors-aggregate's area ratio and roughening depth-are selected to quantify the level of surface preparation. To experimentally evaluate the effect of these two factors on bond behavior, thirty-six concrete block specimens were loaded by direct pullout force until failure. For the normal-strength concrete specimens, the increase to roughening depth increased the bond strength of concrete (C) interface and switched the fracture surface from FRP-concrete (FC) interface to concrete interface. Meanwhile, the effective bond length was decreased. However, the opposite trend was found in high-strength concrete specimens. The effect of aggregate's area ratio was negligible as compared to that of the roughening depth. The quantitative image analysis (QIA) shows that the surface preparation drastically changes the local fracture interface and the pullout force increases with the percentage of C interfacial failure. A design equation is proposed to predict the pullout force of FRP-concrete interface with surface preparation, considering contributions from different failure interfaces. Finally, the bond strength of C interface is calibrated as function of concrete strength and roughening depth, showing satisfactory agreement with the experimental results.