Preparation And Application On Heat-Resisting Inorganic Adhesive Used For CFRP Laminate-Strengthening

At present, the softening temperature of resin adhesive used in the reinforced technique of concrete structure strengthened with Carbon Fiber Reinforced Polymer(CFRP) is less than 80℃, as a result, the fire-resistance property of CFRP-strengthening structure's is very poor, which has become one of the obstacles and hinders the development of CFRP-strengthening technique. An inorganic matrix material named Geopolymer is presented after referring to a lot of references at home and abroad. Geopolymer has many favorable properties, especially for its fire resistance. It has been tentatively proven to be used in CFRP-strengthening technique. Geopolymer and its application in CFRP-strengthening technique are researched in this dissertation, and the main research and achievement are listed as follows:(1) In order to ensure the safety of interface, it is required that the mechanical properties (Including compressive strength and tensile strength and so on) should surpass concrete mechanical properties. In order to facilitate research work, taking the compressive strength of the geopolymer as the main criterion in preliminary research, some laws of influence of kinds and dosages of alkali activations, kinds of sialic materials, through trial mix of two kinds of sialic materials and three kinds of alkali activations, the curing age to the compressive strength of geopolymer are researched .Based on this work, the mixture ratio is optimized. All these provide basis for fabrication of the inorganic geopolymer adhesive is prepared.(2) The microstructure and components of geopolymer are researched and the reaction mechanism is discovered by using Scanning Electron Microscope and X-ray Diffraction. The results indicate that the hydration mechanism of geopolymer is completely different from those of Portland cement. Geopolymer belongs to amorphous body, its micro-structure morphology is granular, pyramid-like, lumpish.(3) In order to explore geopolymer's fire-resistance property, test of residual compressive strength and appearance failure characteristic after high temperature is done, and the test results are compared with the cement stone of ordinary Portland cement. It shows that Geopolymer has better fire-resistantce property but worse volume stability compared with Portland cement, the fireproof upper limitation of geopolymer is between 600℃and 800℃. Analysis on Microstructure reveals that some solid state reaction occurrs when the temperature is between 600℃and 800℃, and some material named akermanite(Ca₂MgSi₂O₇) is generated. As a result, the phase translates from amorphous state to crystalline state.(4) The bond performance between CFRP sheet and concrete is studied by experiment on double-shear test using self-made fixture. The performance of inorganic geopolymer adhesive is determined by shear strength and interface failure characteristic. The results indicate that the interface failure characteristic is not good, and the reason lies in that the inorganic geopolymer adhesive belongs to coarse disperse system and it can not infiltrate CFRP sheet. This is the biggest drawback for inorganic geopolymer adhesive used to paste CFRP. Through comparison, the experimental research on improving adhesive's wettability capacity to CFRP sheet is carried out by choosing slag and compound silicate to prepare the inorganic geopolymer adhesive. The mix ratio is: modulus of silicate M=1.0, the quality ratio of silicate to slag is 12%, and water to slag is 0.35 or 0.42.(5) The wettability capacity between inorganic geopolymer adhesive and CFRP sheet can be improved by soaking and pestling CFRP sheet in adhesive for a period of time. The double-shear test had been done after this processing, it is found that more than 70% area of concrete under contact surface is separated and the shear strength can reach as high as 1.41MPa, the bond performance of inorganic geopolymer adhesive has achieved that of resin adhesive. But the method is not convenient for construction, and the improved measure is put forward. CFRP Sheet is solidified to become plate and then is used for reinforcement. By this measure, not only the better workability can be obtained, but also higher shear strength and much more proper interface failure characteristic are got under the condition that the CFRP plate's planeness is ensured. This approach makes it possible for large-scale use of inorganic geopolymer adhesive in reinforcement project.