Development of ductile composite reinforcement bars for concrete structures

In order to overcome the deficiencies of current composite reinforcement bars such as low elastic moduli, low pre-rupture elongation, brittle fracture as well as high cost, a new core-shell model of hybrid composite reinforcement bar has been developed in this study. In this model, steel and glass fibers are randomly dispersed across the cross section of the core while Twaron and carbon fibers are placed within the shell to improve the elastic modulus as well as to serve as a shield for protecting the glass fibers from alkaline attack; and the steel fibers from moisture and chloride induced corrosion. Glass composite reinforcement bars and hybrid composite reinforcement bars were fabricated by hand winding method. The tensile modulus and strength of the new hybrid reinforcement bars were determined to be 142 GPa and 628 MPa, respectively. New hybrid reinforcement bars were also conditioned in different alkaline environments and were evaluated for their alkaline resistance properties. Compared with glass composite reinforcement bars, the new hybrid composite reinforcement bars possess characteristics of alkaline resistance, good ductility and increased modulus of elasticity, while the material costs of such hybrid composite reinforcement bars are slightly higher than the glass composite reinforcement bars.