What is the construction process of Carbon Fiber Reinforced Polymer?
As we all know, carbon fiber reinforced polymer(CFRP) is also known as carbon fiber cloth, carbon fiber fabric, carbon fiber woven cloth, etc. With the development of the times, more and more places use carbon fiber cloth. So, what is the construction process of CFRP reinforcement? What should be paid attention to in the construction of carbon fiber cloth? Let's explore the answer together!
A、 What is the construction process of CFRP reinforcement?
1、 Do a good job of construction preparation; 2. Treat the surface of concrete; 3. Brush the primer; 4. Do a good job of local surface leveling; 5. Prepare the impregnating adhesive; 6. Paste the carbon fiber cloth; 7. Cure and maintain; 8. Do a good job of inspection.
B、 What should be paid attention to in the construction of carbon fiber cloth?
1. The compressive strength of the base concrete of the strengthening Department of carbon fiber cloth must be greater than C15.
2. When the carbon fiber cloth is lapped, it must be operated in the direction of the fiber, and the lap length must be more than one meter, so it is better to arrange it longer.
3. The construction temperature of carbon fiber cloth should be controlled between 5 ℃ and 35 ℃.
4. Since carbon fiber cloth is a conductive material, it is better to keep away from electrical equipment during construction, and take some reliable protective measures if conditions permit.
5. Carbon fiber cloth must avoid bending during construction.
6. Carbon fiber sheet and other accessories should be sealed when they are stored, and must be kept away from direct sunlight.
7. During the construction of carbon fiber cloth, good ventilation effect must be ensured indoors.
8. Construction personnel must wear gloves, masks, etc., and take corresponding protective measures.
Technology and construction points for concrete columns strengthened with carbon fiber
Carbon fiber is the most widely used and popular reinforcement material in the whole construction and concrete industry. This reinforcement technology rised in the 1980s and developed rapidly in China in the late 1990s. Many domestic and foreign scientific research institutions and universities have carried out a lot of research on the new technology of strengthening concrete with carbon fiber reinforced polymer(CFRP). With the deepening of the experimental research, the application scope of the reinforcement technology is expanding, and the application technology is improving.
1. Application scope and working condition requirements
The reinforced concrete columns strengthened by CFRP are suitable for columns or rectangular columns with small section (the side length of the section is generally less than 800mm), which can greatly improve the bearing capacity of reinforced concrete columns under axial compression without instability. The precondition of strengthening is that the basic concrete of the component is not damaged, and it still has certain bearing and deformation capacity.
2. Key points of reinforcement construction:
1) The unloading before the reinforced concrete columns is often ignored. When the concrete components are wrapped with CFRP, the strain lag of the wrapped CFRP relative to the concrete column surface often occurs, and the CFRP has not been broken by the tension concrete, which makes the reinforcement effect of CFRP reduce, and the high tensile performance of CFRP cannot be fully exerted.
2) The radius of the corner chamfer of rectangular column shall not be less than 20 mm. It is better to repair the outer convex surface of the column side to reduce the concentrated stress of the corner CFRP. Many tests show that even so, the failure of CFRP still occurs at the corner.
3) It is very important to repair the surface of concrete components, which directly affects the effect of CFRP on the lateral restraint of concrete.
1. The reinforced concrete columns strengthened by CFRP can change the axial stress of concrete into three-dimensional stress, and improve the bearing capacity and deformation capacity of confined concrete, especially for the reinforced concrete columns whose axial compression ratio can not meet the requirements.
2. To improve the bearing capacity and ductility of plastic hinge area, under the repeated action of seismic load, the upper and lower ends of reinforced concrete columns will first appear plastic hinge area, and the bearing capacity and ductility will decline rapidly. After the winding reinforcement with CFRP, the core concrete in plastic hinge area will be greatly improved in the limit strength and deformation capacity.
3. The construction technology content is easy to understand, the process is simple, the restraint effect is good, the corrosion resistance is strong, only needs to protect and maintain the concrete after strengthening.
4. CFRP reinforcement technology is not a universal "prescription", it has its disadvantages: poor high temperature resistance of organic adhesive, high temperature environment and fire rating requirements of buildings can not be used.And CFRP is conductive.
In the world, the research on the application of carbon fiber reinforced polymer(CFRP) in the reinforcement of concrete structures has been widely carried out. In the mid-1990s, these research results have been widely used in many projects. Carbon fiber materials are characterized by high strength,convenient and rapid construction, unlimited construction space, acid and alkali resistance, corrosion resistance, etc. It has more than ten times higher tensile strength and equivalent to the elastic modulus of steel.
In bending reinforcement, the direction of the fiber should be the same as that of the reinforcement;
In shear and seismic strengthening, the fiber direction should be perpendicular to the axial direction of the component;
The strength grade of concrete shall not be lower than C15 in bending reinforcement and shear reinforcement;
The strength grade of concrete should be no less than C10 when the closed bonded carbon fiber is used to strengthen the concrete column;
The effect of carbon fiber reinforcement mainly depends on the bonding process of the fiber.
Light weight, convenient and fast construction, no increase in structural load;
It has high strength and can be flexibly used in bending resistance, closed hoop and shear resistance design;
Good flexibility, not limited by the structure (beams, columns, ventilators, pipes, walls, etc.);
Good durability, strong resistance to chemical corrosion and severe environmental climate change;
High temperature resistance, creep resistance, anti-wear and anti-seismic performance;
It can be applied to a wide range of concrete components, steel structures and wood structures. Structural reinforcement of building beam, column and floor; structural reinforcement of bridge, pier and bridge deck; structural reinforcement of tunnel and chimney; anti-corrosion reinforcement of beach buildings.
Carbon Fiber Reinforced Polymer(CFRP) strengthening technology is to use special structural adhesive(resin) to paste CFRP on the surface of concrete to form a composite structure. CFRP can strengthen and improve the mechanical properties of components or structures of concrete. Strengthening with Carbon Fiber Reinforced Polymer(CFRP) can effectively improve the structure of concrete, like reduce deformation, reduce stress of original structure and crack.