Carbon fibre materials used in the reinforcement and repair of concrete structures began in the 1980s in developed countries such as the United States and Japan. In the early 1990s, China began to focus on the development of carbon fibre production and application. In the area of building reinforcement, carbon fibre applications are more and more widely.

Practice shows that carbon fiber material has strong comprehensive performance, durability and light weight. It is a widely used crack treatment material at present, and its tensile strength is 7-10 times that of steel plate of the same size. Therefore, carbon fiber materials are used in many cases in steel and concrete structures, which can improve the overall performance of the structure.

I. Examples

There are 125 30 m prefabricated T-beams in a bridge project, of which 75 are middle beams and 50 are side beams, all of which are made of C50 concrete. On May 6, 2008, after inspection by professionals, it was found that the prefabricated T-beams had cracks in both horizontal and vertical directions. After inspection, the main causes were as follows.

(1) The temperature change in May in the area where the project is located is very obvious, and it can even rise directly from 10 C to more than 30 C. Because the temperature varies greatly, in many cases it is too late to adjust the mix proportion of concrete, but the winter mix parameter is still used, which causes serious hydration heat and cracking problems.

(2) The Prefabrication Yard is located in the middle of the valley. When the wind enters the space, the speed becomes faster. The water on the surface of the building structure will evaporate, which will cause surface tension and cracking.

The design scheme of bridge reinforcement can only be implemented after consultation and determination by owners, design units, supervision units and construction units. For 30 mT beams with serious diseases, a total of 13. According to the specific situation of the project, the grouting method and carbon fiber reinforcement method are selected to reinforce the whole part. The following is a detailed description of the process of carbon fiber reinforcement.

2. Construction Method of Carbon Fiber Reinforcement in Bridge Maintenance

According to the specific requirements of the project, 300 g/m2 and 0.167 mm CFRP are selected as reinforcing materials to ensure that all technical parameters of CFRP can meet the requirements. Carbon fibre adhesives should choose products that can meet the requirements of carbon fibre materials and meet the requirements of national standards, and the selected materials such as carbon fibre cloth and carbon fibre adhesives have quality certification documents to ensure the quality of materials to meet the standards.

1) Construction technology of CFRP reinforcement: surface cleaning resin coating at the bottom surface leveling pasting CFRP closed construction.

2) Main construction methods of carbon fiber cloth: crack location needs surface grouting and grouting construction, and surface leveling treatment to ensure that its dryness and cleanliness can meet the requirements, and then coated with resin materials.

Carbon fibre primer needs to be made according to the prescribed ratio, and then uniformly applied on the surface of the structure with a roller brush or a brush, with a thickness of 0.4mm, while ensuring smoothness and uniformity.

If the surface of concrete is uneven, the scraper should be used for leveling. The corner position should be treated as a smooth circular arc structure with a radius greater than 20 mm.

Carbon fibre cloth sticking should be specified in the specific position, and then rolled on the surface by roller to ensure that there are no bubbles in the carbon fibre cloth, and can not damage the carbon fibre cloth material.

Note: If the crack position has been extended to the horseshoe or flange position, the length and width of carbon fiber cloth should be extended appropriately according to the specific situation. For the penetrating crack form with web and rib root position, the transverse position of carbon fiber cloth used in rib plate can be reduced by 15 cm appropriately.

In construction, we should try our best to keep the staggered arrangement of CFRP and avoid obstacles when pasting. If the obstacles have to be interrupted, appropriate treatment should be carried out at the root of CFRP.

The outer layer of carbon fiber cloth needs to be coated with a layer of anticorrosive material.

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