Polypropylene-Based FRP Rebars, OFBG Sensors And Their Performance For Civil Infrastructures

FRP (Fiber Reinforced Polymer) materials have gained much more interests of the researchers in civil engineering for their light weight, high strength and excellent durability performance. While, as we know, common FRP rebars or plates used for reinforcing or strengthening in civil engineering are mostly made by fiber reinforced thermosetting polymer (FRSP) materials. But FRSP have so many disadvantages such as: poor integral flexibility, no premonition before break, environment pollution and so on. Further more, FRSP materials can not be reshaped so that many of the special shapes as bending rebar or hoop rebar cannot be easily obtained. Rebars or plates are mostly prefabricated in factory, and they can not be handled at site. For above reasons, we developed and successfully fabricated Glass Fiber Reinforced Polypropylene(GFRPP) according to another FRP system—Fiber Reinforced Thermoplastic Polymer (FRTP). And the fabricating techniques, physical and mechanical performance, durability and bending techniques have been systematically studied. Meanwhile, we have also invented and produced GFRPP-OFBG composite rebar and PP-OFBG strain sensor for asphalt pavement strain monitoring on the base of good understanding on the performance of the GFRPP rebar and resin matrix, experiments and project application have been performed. The main works of this dissertation are as follows.Above all, the fabricating techniques of GFRPP rebar have been studied. And theoretical analysis on the impregnation of fibers and molten resin has been done, the appropriate impregnation techniques have been defined; the fiber and resin contents and resin mixture ratio have also determined under the needs of fabricating process and performance of the products. Round and ribbed GFRPP rebar have been successfully fabricated through ourselves-designed online molten impregnation thermoplastic pultrusion equipments and thermoplastic pultrusion-enwinding techniques or thermoplastic pultrusion-molding techniques. And the processing parameters have been defined, and their effects on the performance of the products have been studied. Some defects inside or outside of GFRPP rebars have been analyzed.Secondly, some physical and mechanical performance of GFRPP rebars with different surface-treatment and fiber/resin mixture ratio as tension strength, tension modulus, interlamination shearing strength, impact toughness and hygroscopic coefficient have been tested, and some comparison study have been done to those of fiber reinforced thermosetting polymer rebars. As we know, the radial strength of FRP rebar is very low, and it can be easily broken by the holders of the testing machine when being tensioned. Because of these, we did some finite element method (FEM) analysis by ANSYS software on the anchors of FRP rebars, and a kind of proper anchor have been designed and fabricated.Thirdly, bending theoretical analysis on GFRPP rebars have been performed and the specific techniques on making GFRPP bending rebar or GFRPP hoop rebar have been studied; and we also invented and produced a simple and flexible"GFRPP rebar bending machine"according to the performance of GFRPP rebar. And it was experimentally studied bonding performance of some kinds of bent rebar with concrete bonding specimens so that we can know whether bent GFRPP rebar can meet the needs of civil engineering. Results shows that the strength in bending part of GFRPP rebar can reach 30%~60% of the ultimate tension strength, and with the strengthening of epoxy resin, this strength can reach or above 70% of the ultimate tension strength.Fourthly, to study the corrosion resistance problem of GFRPP rebar, corrosion tests of GFRPP rebars have been done in alkali solution individually at 20, and 60℃accelerating temperature and in salt and acid solution at 60℃accelerating temperature. Some UV-light accelerating ageing experiments also have been done to test the UV-light resistance of GFRPP rebars. The physical and mechanical performance such as tension strength, tension modulus, interlamination shearing strength, impact toughness and hygroscopic coefficient have been tested to evaluate the corrosion or UV-light ageing abilities. Durability life of the GFRPP rebars serving in 10℃, RH=100%, without stress condition was predicted individually by tow kinds of FHWA methods. Also, UV-light accelerating ageing experiments have been done to test the effects of carbon content on the UV-light resistance of GFRPP rebars, and the interlamination shearing strength, impact toughness have been tested at different age. The results tells that carbon as a light stabilizer can improve the UV-light resistance of GFRPP rebars, so it can help to prolong the period of storage and service.Fifthly, we successfully fabricated GFRPP-OFBG composite rebar by embedding bare OFBG into GFRPP rebar during pultrusion process, and also the mechanical and sensitive properties have been studied."Tow OFBG method"was used in monitoring the inner strain and temperature of GFRPP rebar when producing GFRPP rebar with thermoplastic pultrusion techniques, which can give reference on deciding the processing parameters. And also, we packaged bare OFBG with PP resin by extrusion techniques; the sensitive property of PP-OFBG was excellent. Online monitoring work with"Tow OFBG method"has been done to measure the inner strain and temperature changes of PP-OFBG during extrusion process. Based on these, large-scale strain measuring sensor was discussed.Finally, based on the PP-OFBG sensing element above, we developed a novel PP-OFBG strain sensor special for asphalt pavement strain measuring because of the same modulus of PP resin and asphalt concrete. Its sensitive property was tested, and 3 asphalt concrete beams were prepared for four point bending experiments. Through comparing the theoretical calculation and static and dynamic loading tests, we found that this novel PP-OFBG strain sensor can reflect the deformation of asphalt concrete well. We also cooperated finishing a steel-asphalt girder deformation monitoring experiment, 90 sensors were embedded or welded. Through designing, monitoring and analyzing we found that as asphalt pavement measuring sensor, PP-OFBG can give stable and accurate results, which can meet the needs of asphalt pavement strain measuring well.