1 Research on carbon fiber repair and reinforcement of concrete structures at home and abroad

Carbon fiber is a high-tech material developed by the aerospace industry and has been used in aerospace in the 1970s. Japan, the country with the earliest carbon fiber application research, is a major carbon fiber producer, and its output accounts for more than half of the world's total output. Japan is a country prone to earthquakes. Many buildings, bridges, and public facilities were severely damaged in the earthquake. Carbon fiber sheet repair and reinforcement technology has the characteristics of safety and reliability, simple and rapid construction, and good durability. It plays a great role in the process of seismic reinforcement and earthquake damage prevention. Although my country's research on carbon fiber reinforcement and repair of concrete structures has been carried out relatively late, it has been applied relatively early, and relevant departments have formulated technical regulations on carbon fiber reinforcement.

2 Carbon fiber is an ideal material for bridge reinforcement

Carbon fiber is a fibrous carbon material. It is a high-tech product manufactured through a special process at a certain temperature and has many characteristics. Such as aging resistance, stable physical properties, corrosion resistance, its tensile strength is several times that of steel, and its specific gravity is only a few fractions of steel. Carbon fiber has good resistance to salt, acid and alkali, and carbon fiber sheet is reinforced. The test piece is immersed in a certain temperature of salt water for a long time, and the strength will not be reduced. After soaking in a certain concentration of sulfuric acid solution for several months, the strength will not decrease. Soaking in an alkaline solution at a certain temperature for ten days will not reduce the strength

Good water resistance: immersion at a certain temperature for one month, the strength will not decrease.

Good temperature stability: The carbon fiber sheet can be used for a long time under a wide temperature range, and the strength will not change.

Anti-aging and anti-ultraviolet rays: The strength and adhesive performance of the carbon fiber sheet hardly change in half a century, and there will be no loss of tensile strength. This is obtained after a natural exposure test and an accelerated exposure test, and then an infrared spectrometer is used to evaluate the performance of the test piece after the test.

3 Features and advantages of carbon fiber reinforcement technology

3.1 Good chemical stability

Carbon fiber has good water resistance, strong acid resistance, alkali resistance, and UV resistance, and it has the ability to use different weather conditions. If a layer of fireproof coating is added to it, it can play a role of fire prevention. Because of the good chemical properties of carbon fiber sheets and can adapt to various harsh environments, the life of the structure can be extended.

3.2 Excellent mechanical properties

With its superior mechanical properties, carbon fiber is used in various forms of structural reinforcement, such as bending resistance, shear resistance, compression resistance, seismic resistance, wind resistance, fatigue resistance, and it also has a good control effect on deflection and crack expansion. . Therefore, it can be used well in various forms of bridges and buildings.

3.3 Simple construction process

Carbon fiber can be used in the operation of small power tools and has a simple construction process. If there are fewer types of work, there will be less labor; short construction period will lead to faster progress. Relevant data shows that when the traffic is constantly shaking, its reinforcement effect will not be affected, which can greatly shorten the time for construction to cut off traffic, and has better economic and social benefits.

3.4 Light and high strength materials

The carbon fiber material is light in weight and high in strength, which can reduce the mass and volume of the structure without changing the shape of the structure. It is particularly convenient to paint with the required colors, and there will be no traces of reinforcement, which is incomparable to other methods.

4. Reinforcement method of carbon fiber sheet

Anti-crack reinforcement: paste along the vertical direction of the crack.

Shear reinforcement: When pasting, keep the u-shaped loop wrap with the ground, or vertically on the two sides of the beam, which is equivalent to strengthening the shear stirrup.

Flexural reinforcement: The carbon fiber sheet is attached to the side under tension.

Shear wall reinforcement: Paste carbon fiber sheets along the direction of shear reinforcement on one or both sides of the shear wall.

Reinforcement of the columnar center compression member: the column center ring wraps and pastes.

5. Key points of construction for reinforcement of carbon fiber sheet

During construction, the carbon fiber sheet cannot be bent or bumped to avoid carbon fiber breakage. This is because carbon fiber filaments are very brittle and thin, and the filaments break easily. For the longitudinal joints of carbon fiber sheets, the overlapping place must be separated from the maximum section of the component stress, and must be overlapped a certain distance. When multi-layer pasting is carried out, the overlapping of each layer cannot be carried out in the same position, and the layers are also Stagger a certain distance. The pasted carbon fiber sheet should be flat and dense, without warping or hollowing. The surface of the concrete structure where the carbon fiber sheet is pasted should be dense and flat. The exposed steel bars should be rust-proof and derusted, and concrete cracks should be treated to a certain extent. To smooth the paste surface, the corner diameter should be polished to have a

Set the length of the fillet while keeping the surface dry and clean. Different types of epoxy putty, primer, epoxy resin for bonding, etc. can be selected according to the construction climatic conditions and different temperature conditions. Able to carry out construction work in the constantly vibrating traffic. Vibration will not have any negative impact on the load condition of the specimen during the process of the carbon fiber sheet bonding during the curing of the concrete binder.

6. Conclusion

In short, with the continuous development of my country's economy and society and the increasing traffic volume, many of the reinforced concrete bridges built in the past can no longer meet today's needs, and many diseases of this kind have appeared. Reinforcing old bridges is a relatively complicated project, and it also requires an important material to be used in the reinforcement. The price of carbon fiber is gradually decreasing due to its unique characteristics and quality, and mature application environment. Moreover, carbon fiber reinforcement technology has obvious advantages in accordance with actual conditions, and it has attracted more and more attention in bridge reinforcement. I believe that in the future bridge reinforcement, carbon fiber will be widely used to provide good materials for my country's bridge construction and lay a good foundation for the construction of a well-off society in my country.