Bond Durability of FRP Bars Embedded in Fiber-Reinforced Concrete

A research program was initiated to develop a nonferrous reinforcement system for concrete bridge decks using continuous fiber-reinforced polymer (FRP) bars and discrete, randomly distributed polypropylene fibers. This hybrid system may eliminate problems related to corrosion of steel reinforcement while providing requisite strength, stiffness, and desired ductility, which are shortcomings of the FRP reinforcing system in plain concrete. This paper presents the results of a part of this research program [i.e., the long-term bond behaviors of this FRP/fiber-reinforced concrete (FRC) hybrid system]. Bond durability for the FRP/plain concrete system that served as a reference is also reported. Test results indicated that ultimate and design bond strength experienced noticeable degradation when exposed to combined environmental conditioning, including freeze-thaw cycles, high temperature (60°C), and deicing salt solution. Test results showed that bond durability significantly improved owing to the restriction of the concrete crack by the addition of polypropylene fibers. The larger specimens with thicker concrete cover and relatively smaller direct exposed area to the solution of sodium chloride (NaCl) showed better bond durability. Comparing glass FRP specimens with carbon FRP specimens, it was found that bond degradation was tightly correlated to the degradation of FRP bars.