Carbon fiber composite material(CarbonFiber Reinforced Plastic, CFRP for short) is a new high-strength material, and its research and application in the field of civil engineering have developed rapidly in recent years. The technology for structural strengthening and repairing concrete structures is to apply this high-performance carbon fiber material to civil engineering, and stick the carbon fiber sheet to the surface of the concrete with a matching resin binder, so as to achieve the purpose of structural reinforcement and improvement of mechanical performance. Compared with the traditional structural reinforcement technology, this method is widely used in structural reinforcement and reconstruction projects at home and abroad due to its advantages of light weight, high strength, strong corrosion resistance and durability, convenient construction, and small impact on the structure.

Design basis of carbon fiber composite reinforcement scheme

Carbon fiber composite materials strengthen concrete structures and components, usually in the following ways:

(1) Paste carbon fiber along the main axis of the component to improve the bending resistance of the front section of the component.

(2) Paste the carbon fiber in the direction perpendicular to the main axis of the component, and the carbon fiber and the original stirrup share the shear force to improve the shear capacity of the component.

(3) Paste carbon fiber in the direction perpendicular to the main axis of the component to improve the ductility of the reinforced part and improve its seismic performance. At present, the most widely used method in domestic engineering is the first method, that is, strengthening and repairing to improve the load-bearing capacity of the front section of the beam and slab, so that it can meet the functional requirements of use.

Mechanical properties of carbon fiber composites

The reinforcing materials of fiber reinforced composite materials (FRP) mainly refer to carbon fiber, aramid fiber, and glass fiber. Because carbon fiber composite materials have the advantages of light weight, high strength, good corrosion resistance, easy construction, etc., especially for improving the bearing capacity and ductility of structures or components, they have a unique effect, so they have been widely used in structural reinforcement, repair and transformation. .

Construction superiority of carbon fiber composite reinforcement technology

During the construction of reinforced concrete structures with carbon fiber composite materials, due to the light weight of the materials (the commonly used carbon fiber cloth is only 200-~600g/m2), packaging, transportation, storage and construction are very convenient. Compared with other reinforcement methods such as electrochemical reinforcement and bonded steel reinforcement, it has great advantages in terms of construction performance.

1 Short construction period

Carbon fiber composite materials do not require large-scale machinery and equipment to reinforce concrete structures. Under the premise of ensuring construction quality and no accidental interference, the time required under the same conditions is not enough. At present, the method of sticking steel plates widely used in China requires 1/2 of the time. In the case of good construction organization in China, 1000m2 of work can be completed in 10 working days. The finished carbon fiber cloth is a kind of fabric, the width can be 20, 30, 50cm, the length is 50-100m, and it is packaged in roll form. When used on site, it can be cut arbitrarily with scissors or blades as needed, unlike steel plates that require special cutting tools. According to relevant statistical data, the same method of sticking reinforcement, sticking carbon fiber composite material is 4 to 8 times the work efficiency of sticking steel plate construction.

2 Small construction interference

The construction of carbon fiber composite reinforced structures can be implemented in a small space. Except for the need to control the dust during concrete surface treatment, there is almost no interference with the normal use of general structures. When carrying out carbon fiber composite reinforcement construction on bridges and roads, traffic can be uninterrupted.

3 Easy to guarantee construction quality

The construction operation of the technology of reinforcing concrete structures with carbon fiber composite materials is convenient, and the effective bonding area of carbon fiber composite materials can basically reach 100% under normal construction conditions. And the on-site inspection is convenient, even if there is a small hollow drum, it can be remedied by needle injection method, and the construction quality can be effectively guaranteed. Due to the short construction period and high efficiency of carbon fiber composite materials to reinforce concrete structures, the materials are processed manually on site: there is no loss of large and medium-sized equipment. The inspection is convenient and fast, and the construction can be carried out in a small space at the same time, which basically does not affect the normal use of the structure. The construction is convenient and the construction period is short. This method can be used to reinforce the shape of various structural members. At the same time, due to the light weight of the material, the structure will not increase the weight after reinforcement, and the appearance size and shape of the structure will not be changed. Compared with other reinforcement methods, it saves a lot of mechanical labor costs, labor costs and inspection costs.