Carbon fiber fabric strengthening

With the increase of the service life of the building or the change of the service property, it is necessary to reinforce the structure in order to meet the service function of the building. For the buildings built before, because of the low design load standard, the bearing capacity is generally insufficient, and some buildings are far from reaching the design life, the durability of serious degradation, affecting its bearing capacity and service life. Therefore, the adoption of appropriate reinforcement and renovation technical measures can improve the bearing capacity of the building, to meet the performance of the building.

The project was recovered by the government, decided to residential areas as affordable housing, part of the housing as low-rent housing to provide low-income families. In order to meet the government's requirement, the low-rent housing covers an area of less than 50 square meters. Each cottage has its own door, bedroom, kitchen, toilet and other facilities. The existing cottage is transformed from one staircase, two households to one staircase and three households. Some structures need to be strengthened. It is decided to adopt carbon fiber sheet reinforcement after comparing the schemes. CFRP reinforcement has the advantages of saving space, simple construction, high efficiency, no wet operation, less construction site occupation, no need for site fixing facilities, easy construction quality assurance, obvious advantages in construction period and construction conditions, basically no increase in structural size and weight, corrosion resistance, good durability and so on.

Main material -- properties of carbon fiber fabric

CFRP has excellent physical and mechanical properties. Carbon fiber sheets used to reinforce concrete members are made of carbon fiber materials through a certain manufacturing process and a specific resin composite, which is a soft sheet material made of carbon fiber filament warp knitted. When carbon fiber cloth is woven, a large number of carbon fiber filaments are evenly spread along a main direction, forming a very thin carbon fiber cloth which is stressed in the direction of the main fiber. The standard value of tensile strength of CFRP should be greater than 3400Mpa, and the elastic modulus is greater than 2.3 * l0⁵Mpa.

Carbon fiber cloth reinforcement technology is to use carbon fiber cloth and special structural adhesive to reinforce the building components, the technology used carbon fiber cloth strength is about 10 times the ordinary secondary steel. The thickness is only about 2 mm, and the cross-section of the component is basically not increased, so the carbon fiber cloth can work with the original component. Comprehensive analysis of physical and mechanical properties of materials, in order to maximize the advantages of materials themselves, materials are suitable for building structures as tensile or prestressed flexural members, especially for pure tensile members, building reinforced carbon fiber materials are mainly subject to tensile stress, restricting the development of cracks.

Matters needing attention

1. Before surface treatment and bonding of CFRP sheets, the location of reinforcement design should be placed in line.

(2) Carbon fiber sheets should be cut according to the design requirements, and the width of the cut fabric should not be less than 150 mm and not less than 100 mm.

3. Wipe the surface of carbon fiber sheet to no dust. If you want to paste two layers, wipe both sides of the bottom carbon fiber sheet clean.

(4) Clean wiped carbon fiber sheets should be immediately brushed with adhesive resin, the adhesive layer should be convex, the average thickness is not less than 2 mm.

5. The carbon fiber sheet coated with adhesive resin should be gently pressed to the position where it needs to be pasted. The rubber drum is used to compact uniformly and smoothly along the direction of the fiber sheet, which makes the resin overflow from both sides and ensures the compactness without cavity. When parallel bonding of carbon fibers, the pores between the two pieces should not be less than 5mm.

(6) When sticking two layers of carbon fiber sheet, it can be pasted continuously. If continuous bonding is not possible, clean the bottom carbon fiber sheet before starting.

7. Resin preparation should be in the container according to the proportion specified in the product instructions, stirring evenly with a stirrer to uniform color. No oil and impurities should be used in mixing containers. It is advisable to determine the amount of each resin in accordance with the actual temperature of the site and strictly control the use time.

(8) In order to ensure the quality of the adhesive, different types of adhesive resin should be used in different seasons and at different temperatures, so as to effectively control the operating time and curing time of the resin construction.

Prospects for carbon fiber reinforcement technology

Carbon fiber used in the repair and reinforcement of concrete structures has been developing rapidly. The main reason is that there are many advantages in the reinforcement of carbon fiber sheets.

A) construction is simple and fast, without template, fixture, support and so on.

B) the weight of the epoxy resin is very light, and the influence on the weight of the structure is negligible.

C) can be used to reinforce various structural shapes.

D) can be pasted in multiple layers. It can be overlapped in one place according to the design requirements.

Concluding remarks

With the decrease of bearing capacity, the decrease of concrete strength or the need to improve the seismic capacity and repair the cracks in buildings due to various reasons, CFRP reinforcement method has good effect, high strength, high efficiency, wide application, easy quality assurance, excellent corrosion resistance and durability. And this technology has many advantages, such as simple and fast construction, safety and reliability, good durability, can adapt to a variety of complex structural shapes, without affecting the appearance of the original structure, and so on.