The Experimental Research On Bond-Slip Performance Of GFRP Bars Embedded In Fiber Reinforced Concrete

Deterioration of reinforced concrete structures has become a serious problem, especially for the structures in the ocean environment. This situation is due mainly to corrosion of reinforcing bars embedded in concrete. A long term and effective way to solve this problem is to use fiber reinforced polymer(FRP) reinforcing bars of alternative. FRP bar is a kind of new composite material with high tensile strength and corrosion resistant capability. Good bond performance of FRP bar embedded in concrete is the base of structure in the load, and is one of the emphases of design,using or popularize for FRP structure.Becouse of the difference between FRP bar and steel bar in the mechanical properties and exterior, the bond stress of FRP bar embedded in concrete is not as good as steel bar embedded. How to improve the bond-slip performance of FRP bar become a hotspot problem. Some research result indicate that adding fiber to concrete can enhance the bond strength of FRP bar embedded in concrete; using self-compacting concrete(SCC) can improve the bond strength of FRP bar embedded in concrete for the good workability of it. For the popularization of SCC, many problems must be thrash out, such as optimization of the mix design of self-compacting concrete and the safety of reinforced self-compacting concrete structures and so on.On the basis of summarizing great deal of other researches, this paper first carry out the mix ratio and workability of C40 and C80 SCC. To assure the workability such as fluidity, ability of filling, ability of resistance to segregation of the fresh self-compacting concrete, numerous tests have been done.Then by pull-out tested to study the bond and anchor behavior of GFRP bars embedded in fiber reinforced concrete, including failure modes, bond strength and slip; contrast the bond-slip performance of GFRP bar with steel bar in the same matrix; factors that influence the bond-slip performance of GFRP bar. Experiments and analysis show that adding macro polypropylene fiber to the concrete can enhance the bond strength, and increase the slippage of GFRP bar embedded in concrete; in the same condition, the bond strength of GFRP bar embedded in concrete is 60%～65 % that of steel bar, and it can be enhanced 10% by adding fiber to concrete; the bond-slip performance is influenced by type of fiber,diameter of bars,embedment length and so on. Finally based on the test results and former works, a new equation for bond strength and development length of GFRP rebars is proposed in this paper, which takes types of GFRP bars, strength of concrete, diameter of GFRP bars and embedment length in to consideration. In addition, after concrast the test result and several models for bond-slip relationship, a models for bond-slip relationship is proposed and provide principles for design code.