Thermosetting FRP Composited Rebars And Their Performance For Civil Infrastructures

FRP(Fibre Reinforced Polymer)rebar becomes the substitution of steel rebar in some civil infrastructures, for its light weight, high strength and especially excellent durability performance. Against the problems of applying FRP rebar in civil infrastructures, this dissertation develops ribbed FRP rebar fabrication devices, and fabricates a series of new style of FRP rebars, such as steel cable-GFRP (SGFRP) composited rebar, ribbed FRP rebar and BFRP rebar. To the main type of FRP rebars this dissertation systematically studies bonding performance, durability and intelligent properties composited with FBG. Main works of this dissertation are followed as:1. New types of FRP composited rebar development and their basic properties. Against low modulus, high price and durability problem of FRP rebar applied in civil infrastructures, this dissertation individually invented and developed steel cable-GFRP (SGFRP) composited rebar and basalt fibre FRP (BFRP) rebar, and done experimental investigation of their mechanical and durability performances. The results indicate that SGFRP rebars produce more than 50% modulus improvement comparing to GFRP rebar, and exhibit good durability performances in acid, alkali and saline solution; BFRP rebars show equivalence tensile properties to GFRP rebars, but bad durability performances in acid, alkali and salt solution, especially in alkali solution. The durability performance of BFRP rebar is caused by hydrolyzation of silane coupling agent on the surface of basalt fibre; To improve bonding performance of FRP rebar with concrete, this dissertation developed pull-winding ribbed FRP rebar fabrication devices and fabrication process, done rib style and spacing standardized test, and fabricated diverse of ribbed FRP rebars. The rib standardized test result defines that optimal rib of ribbed FRP rebar is fibre bundle inverse double winding with 1 time diameter pitch.2. Mechanical and durability performances of magnetism curing pultrusion GFRP rebar. According to modifying effect of magnetic field to resin, through modification of FRP pultrusion process and equipments, this dissertation developed FRP rebar magnetism curing pultrusion process, studied the effect of fabrication magnetic field intensity on mechanical performances of fabricated GFRP rebar, and confined the optimal intensity of curing magnetic field. Through durability contrast test of GFRP rebars fabricated with optimal curing magnetism intensity and without magnetic field in 80℃water, according to water-absorbing capacity and interlaminate shear strength, the effect of magnetism curing on the durability performance of GFRP rebar was studied. Experimental results show that magnetism curing can improve GFRP rebar interlaminate shear strength, compression strength and durability in water.3. Bonding performance of FRP rebars with concrete and multi-factor influence. Temperature disposal, corrosion environment and sustained load action effects on bonding performance of ribbed GFRP and SGFRP rebars with concrete were studied. Firstly, it was experimentally studied the bonding performance of two kindsΦ8mm FRP rebar andΦ12mm steel rebar with concrete individually under 70℃, -30℃and after 200 hours of 70℃treatment three kinds of temperature condition; Next it was experimentally studied bonding performance of two kinds FRP rebar with concrete bonding specimen in 60℃alkali solution individually after 1, 2 and 3.5 months of soaking, which analyzes the effect of alkali environment on the bonding performance of FRP rebar with concrete; Finally it was experimentally studied sustained load bonding performance of two kinds of FRP rebars with concrete under 60% and 75% of maximum bonding load, which analyzes the effect of sustained load on bonding performance of FRP rebar with concrete.4. FRP rebar durability life predictions. Against the alkali resistance problem of GFRP rebar, corrosion tests of round and ribbed GFRP rebars were done in alkali solution individually in 34, 60 and 80℃accelerating temperature. Relation of tensile performances and corrosion time of two kinds GFRP rebar under different temperatures was analyzed, and durability life of two kinds GFRP rebar serving in 10℃, RH=100% concrete, without stress condition was predicted individually by TSF and FHWA method; According to the corrosion test ofΦ8mm ribbed andΦ7mm round SGFRP rebars in 60℃acid, alkali and salt solution, it was analyzed two kinds SGFRP rebar corrosion resistant property in various corrosion solutions. Durability life prediction results show that durability life of round GFRP rebar is about 4 times of ribbed GFRP rebar's. 5. Residual stain of FRP-OFBG smart rebar in fabrication process and its effect on smart rebar sensing character. Against axial residual strain in unidirectional FRP rebar, it was theoretically analyzed residual strain of various constituents introduced in smart rebar fabrication process. Utilizing double FBGs method, the temperature and strain in GFRP rebar pultrusion fabrication process were on-line monitored. Through experimental analysis of sustained load and room temperature unstressing action influence on residual strain of smart rebar, sensing stability of smart rebar is studied. This dissertation analyzed deterioration reason of FBG spectrum in smart rebar, and introduced high temperature post treatment method to settle problem of double or multi peaks phenomenon of FBG in smart rebar.