Experimental Research On Concrete Beams Strengthened With Carbon Fiber Sheet Using Metakaolin-based Geopolymer

The technique of carbon fiber sheet(CFS) strengthening concrete structure has been widely used in the structure strengthening field. Compared with other strengthening techniques, CFS strengthening technique has many advantages, including high strength, light weight and ease of construction. However, the epoxy resin used to stick CFS will intenerate soon under high temperature, which seriously affects the fire safety of strengthening structure. Metakaolin-based geopolymer, which generally has favorable fire resistance capacity, mechanical properties and dimensional stability, is presented in a lot of references at home and abroad. In this dissertation, geopolymer was adopted to replace epoxy resin in CFS-strengthening concrete beams.Main research works involved in this dissertation were:One kind of geopolymer was made at room temperature and atmospheric pressure from activated kaolin with alkali activator. The influences of the calcining temperature and the constant temperature time of kaolin, the concentration and modulus of sodium silicate, and the water-binder ratio on the compressive strength, the mini-slump extension and the setting time of this geopolymer were investigated by using orthogonal test. Finally, the applicable geopolymer was optimized of which the compressive strength, the mini-slump extension and the setting time satisfied the actual need.Through tensile lap-shear tests and double-side shear tests, the tensile lap-shear strength and the bonding performance of the geopolymer and epoxy resin at elevated temperatures were compared. 4 CFS-strengthened concrete beams and an unstrengthened one were tested at room temperature, as well as the effectiveness of the geopolymer in strengthened beams. Test results showed that: the mechanical properties of the geopolymer were much better than those of the epoxy resin; the load bearing capacity of a CFS-strengthened concrete beam using geopolymer was close to that using epoxy resin; and the infiltration of the geoplymer in CFS need to be improved in the future.