Carbon fiber reinforcement technology is a new and efficient structural reinforcement technology. It uses epoxy resin adhesive to paste carbon fiber cloth on the wall structure to be repaired along the direction of tension or vertical crack direction, so that the reinforcement patch and the original steel bar Concrete can bear the same force, improve the bending resistance and shear resistance of the structure, so as to achieve the purpose of strengthening and reinforcing the structural components. At present, this technology has been maturely used in developed countries and regions such as the United States, Japan, and Europe, but domestic research and application of it are relatively lagging behind.
1 Characteristics of carbon fiber reinforcement
Improve the bearing capacity and ductility of concrete structures and components, improve their mechanical performance, and achieve the purpose of efficient reinforcement and repair; ②Light weight, basically does not increase the weight of the structure
Reinforcement with carbon fiber cloth has the following characteristics: ① High tensile strength. The excellent physical and mechanical properties of carbon fiber materials can be improved in the reinforcement and repair of concrete structures.
and section dimensions. And it is flexible, easy to cut, and has a wide range of applications; ③The corrosion resistance and durability of the structure can be greatly improved after reinforcement. Experiments show that carbon fiber
Dimensional reinforced concrete structure can resist the corrosion of structures by acids, alkalis and salts that buildings often encounter; ④Short construction period; ⑤Convenient construction. No need for large facilities
There are no industrial structures and turnover materials, no wet operation, less construction site occupation, and good economy.
2 Application Fields of Carbon Fiber Reinforcement
2.1 Flexural reinforcement Carbon fiber materials have high tensile strength and can be used for flexural reinforcement of concrete members. When carbon fiber is used for flexural reinforcement, the fiber bonding direction should be parallel to the main stress direction of the component, and the reduction of the ultimate strength of carbon fiber should also be considered when calculating the flexural bearing capacity of the reinforced structure.
2.2 The research of seismic strengthening experiments shows that wrapping reinforced concrete columns with carbon fiber materials so that the fiber direction is perpendicular to the axis of the column can effectively improve the ductility and bearing capacity of the column, and increase its seismic energy dissipation capacity. In addition, as the main lateral force-resisting member of the shear wall, its failure mode is nothing more than flexural ductile failure or shear brittle failure.
bad. Reinforcement of shear walls with carbon fiber can also significantly improve its ductility and bearing capacity as long as the method is appropriate. Therefore, the seismic strengthening of reinforced concrete structures is an effective field for the application of carbon fiber materials. However, when carbon fiber is used to reinforce columns or shear walls, since carbon fiber itself is a pre-flexible material, it is bonded to the reinforced structure through structural glue, and the reinforced structural concrete must meet certain strength requirements before it is possible to play the role of carbon fiber reinforcement. Effect.
3 Key points of carbon fiber reinforcement process
3.1 The carbon fiber material that uses high-quality binders for building structure reinforcement has excellent mechanical properties, but after the carbon fiber material is woven into carbon fiber cloth, it is difficult for the carbon fiber filaments to work together completely. The filaments are gradually broken until the whole is destroyed. After using the binder, the carbon fiber filaments can work well together, which greatly improves the tensile strength of the carbon fiber cloth. Therefore, carbon fiber reinforcement must first enable the carbon fiber filaments in the carbon fiber cloth to work together.
do. Therefore, the binder plays a key role in the reinforcement of the carbon fiber cloth. It not only ensures that the carbon fiber filaments work together, but also ensures that the carbon fiber cloth and the structure work together.
3.2 Base treatment If the concrete surface has deteriorating phenomena such as shedding, hollowing, honeycomb, corrosion, etc., it should be removed, and the base treatment should be clean, so that the adhesive can be firmly combined with the concrete surface. For the inferior layer with a large area, it should be repaired with epoxy mortar after chiseling. Use a concrete angle grinder, sandpaper and other tools to remove loose matter, oil stains and other sundries on the concrete surface, and the concrete on the base surface of the component should be ground smooth. It is best to wipe the concrete surface with absorbent cotton dipped in acetone. If there is water leakage, it should be treated with water stop and water guide. The quality of the surface treatment of the reinforced structure will directly affect the quality of reinforcement.
3.3 The configuration of the primer is based on the mix ratio of main agent: curing agent = 3: 1 to configure the primer. Put the main agent and the curing agent in the container successively, measure with a spring balance, and stir evenly with an electric stirrer. Determine the dosage according to the actual temperature on site and strictly control the use time. Generally, it will be used up within 20-50 minutes.
3.4 Pasting and control of carbon fiber cloth First, cut the carbon fiber cloth according to the size required by the design, then prepare the impregnated glue, and then apply it evenly on the part to be pasted. It is strictly forbidden to miss the brush, and pay special attention to the edge of the pasted carbon fiber. Then paste the carbon fiber cloth, try not to let the air bond between the carbon fiber cloth and the adhesive when pasting, after confirming that the pasted parts are correct, use a scraper to repeatedly roll along the fiber direction to remove air bubbles, and make the adhesive fully soak the carbon fiber cloth, and use a scraper to scrape the adhesive on the surface of the carbon fiber cloth to make it even.
3.5 Finished product protection and control of unqualified products The surface of the reinforced carbon fiber cloth is protected by plastering or spraying fireproof paint. The on-site acceptance after the construction is mainly to evaluate the bonding quality between the carbon fiber cloth and the concrete. The surface of the carbon fiber cloth is lightly tapped with a small hammer and other tools to judge the bonding effect by the echo.
4 Conclusion
Carbon fiber materials are more and more widely used in structural reinforcement engineering. Among the existing reinforcement methods, carbon fiber materials can effectively
Transmission of new loads, material procurement and construction are simple, simple construction techniques and good results are generally recognized. Carbon fiber reinforcement technology as a technology contains
It is a high-volume building reinforcement method. Compared with the traditional reinforcement technology, the carbon fiber cloth reinforced concrete technology has good comprehensive economic performance.
Dimensional reinforcement and repair of concrete structures has broad application prospects, and has high research value, promotion value and social and economic benefits.