Bond mechanism of FRP rebars to concrete

Abstract

The bond mechanism of Fiber Reinforced Polymer (FRP) rebar to concrete was studied. Five different types of 12.7 and 12.0-mm rebar subjected to different surface treatments were tested, and the bond mechanism was compared with that of untreated FRP rods and ordinary deformed steel. High bond values were obtained for rods exhibiting a stiff deformed surface, on which large deformations were molded by resin, and for rods with a rough surface whereby the roughness has resulted either from winding a helical fiber together with embedded sand particles or from using excess polymer. The bond values recorded were equivalent to or larger than those of ordinary deformed steel. Low bond strength was obtained both for rods with a thick polymeric layer of low mechanical for rods with a thick polymeric layer of low mechanical properties and for rods with smooth surfaces. Different pre-peak and post-peak behavior was observed for the various rods when the entire set of P-s (Pullout load vs. slip) curves were compared. Brittle behavior was apparent wherever the external layer of the rod exhibited large deformations formed in a stiff matrix. Where the surface was rough, more ductile behavior was detected. The wedging of particles into the surface can alter the load-slip behavior, from one of slip-weakening to one of slip-hardening.