Study On The Performance Of FRP Bars And Fiber Reinforced Cementitious Composites

Using fiber reinforced polymer(FRP) bars instead of steel reinforced concrete can effectively solve the problem of steel corrosion, but FRP bars and concrete are all brittle materials, there exists the problem of insufficient ductility, then FRP bars reinforced concrete structures often appear brittle failure. This thesis prepares fiber reinforced cementitious compositesof high toughness with rational fiber content, and using FRCC instead of ordinary concrete as matrix material, trying to improve the ductility and durability of FRP bars reinforced concrete structures, exploring and researching for the application of FRP bars reinforced FRCC structures.This thesis firstly studies the effects of fiber volume fraction and fiber surface treatment on mechanical properties of FRCC, and determines the optimum mix ratio, then studies the flexural performance of reinforced FRCC. Secondly, studies the bond performance of FRP bars with FRCC in different conditions. Finally, analyses the effect of seawater on the interfacial transition zone of FRP bars with FRCC. The experimental study shows that:(1) FRP bars can significantly improve the flexural capacity and ductility of FRCC beams, and the flexural capacity and ductility of FRP bars reinforced FRCC beams are much better than FRP bars reinforced concrete beams. Furthermore, the bending failure form of FRP bars reinforced FRCC beams appears plastic failure, similar with the yield platform feature of reinforced concrete, showing a good ductility. FRP bars used with FRCC can make up for the lack of ductility and make full use of the toughness of FRCC.(2) The bond strength of FRP bars with concrete is comparable with steel, but the bond failure form of FRP bars with concrete is concrete splitting, with little slip amount, lacks of ductility and presents obvious brittle failure. However, the bond strength of FRP bars with FRCC is 60% higher than ordinary concrete, and slip more, the bond failure form is FRCC's cracking and FRP bars' pulling out, FRP bars and FRCC show better bond ductility.(3)Under seawater condition the bond strength of FRP bars with concrete decrease 20% rate than standard curing environment, failure form is still obvious brittle splitting. Under seawater condition the bond strength of FRP bars with FRCC decrease 5% than standard curing environment, failure form is still FRCC's cracking and FRP bars' s pulling out. Under seawater condition, the bond performance of FRP bars with FRCC appears no obvious degradation.(4) Compared with seawater immersion environment, the bond strength of FRP bars and FRCC appears small decline under tide effect, but still shows a ductile failure. However, the bond strength of FRP bars with concrete decrease about 15% under tide effect. Even under tide effect, the bond strengrh of FRP bars with FRCC is 50% higher than FRP bars with concrete under standard curing environment. Therefore, FRP bars and FRCC have good bonding performance and durability, which makes the FRP bars reinforced FRCC structures have a long-term good performance in harsh environment.(5) The alkaline environment can erode BFRP bars and GFRP bars, which leads to the decrease of tensile strength.Seawater corrosion environment makes the interfacial transition microhardness of FRP bars decrease slightly, width becomes larger. Seen from SEM graph, it forms more expansive products Aft,which leads to crack. In general, the mechanical performance and durability of FRP bars reinforced FRCC structures are much better than FRP bars reinforced concrete. FRP bars reinforced FRCC structures have broad prospects in the field of marine engineering, road and bridge engineering which may experience deicing salt.