Hybrid FRP reinforcing bars for concrete structures

During the last two decades, fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated and a number of FRP bars are commercially available. However, major shortcomings of the existing FRP bars are its high initial cost and low elastic modulus compared to conventional steel bars. The main objective of this study using the concept of material hybridization is to develop a viable hybrid FRP bar for concrete structures, especially for marine and waterfront concrete structures. The purposes of hybridization are to increase the elastic modulus of GFRP bar which have function of protecting corrosion and to reduce the initial cost of the FRP bar. Two types of hybrid FRP bar were considered in the development: GFRP crust with steel core and GFRP bar with steel wires dispersed over the cross-section. Using E-glass fibers and unsaturated polyester resins, the hybrid GFRP bar samples of 13 mm in diameter were pultruded and tested for tensile strength. The effect of hybridization on tensile properties of FRP bars were obtained by comparing the results of tensile test with those of non-hybrid GFRP bars. The results of this study indicated that the elastic modulus of the hybrid FRP bar was increased by up to 160 percent compare to non-hybrid GFRP bars. The results of the test program and the future recommendations are summarized in this paper.