Carbon Fiber Sheets for Concrete Repair

Project Overview

The project is a two-story comprehensive high-grade office building with a concrete frame structure, with a restaurant on the first floor and office spaces on the other floors. Due to the need for space reconstruction, it is required to expand the office building without increasing the span modulus of the original office building without adding partitions. And because of the special process requirements, the project used prestressed pipe pile foundation. Based on these constraints of design and actual construction conditions, we chose a construction plan that continued to use the original structural form and adopted a rigid connection between the new and old buildings.

After the design plan was determined, the owner commissioned a professional house appraisal agency to conduct on-site measurement of the original structure performance. According to the inspection results, the steel bar configuration of the original structure, the structural computer analysis of the extension part, and the structural seismic check results, it is found that the original structure has 4 beam sections with insufficient flexural margin and needs to be reinforced.

According to the construction conditions on the site, the carbon fiber bonding method or the steel bonding method is preliminarily selected for reinforcement.

The reinforcement principle of carbon fiber sheet

Carbon fiber sheets are used to reinforce the building structure by sticking the carbon fiber sheets to the surface of the building structure by using its supporting resin. The shear strength of the bonding resin is used to transfer the load borne by the concrete component to the carbon fiber sheet, so that the post-bonded carbon fiber sheet and the original reinforced concrete component can bear the external load force together. The reinforcement finally produces a superimposed force effect, and the carbon fiber sheet used for reinforcement is equivalent to the reinforcement of the building structure.

The characteristics of carbon fiber sheet reinforcement and its comparison with bonded steel reinforcement technology

(1) Carbon fiber sheet reinforcement construction is convenient, efficient, and has good operability. There is no need for bolts and rivets to fix during the reinforcement construction, and it is laid and pasted on the required parts, which has little disturbance to the existing structure, will not affect the integrity of the existing structure, and the construction quality is easy to guarantee. The operation of bonding steel reinforcement technology is relatively complicated. The second floor of this project and the lower part of the roof beams are designed without a ceiling, the structure is exposed, and the reinforcement scheme with small changes to the original structure is the first choice.

2) Carbon fiber sheet reinforcement basically does not increase the permanent load of the structure or increases little. After the carbon fiber sheet is pasted, the weight per m is less than 1.0 kg, and the thickness of the pasted layer is only 1 mm. After reinforcement and repair, the weight and size of the existing structure are basically not increased.

3) Bonded steel reinforcement technology cannot be used in salty soil environment, marine environment, and chemical erosion environment. Therefore, it is restricted in the reinforcement of corrosion projects in underground structures, water supply and drainage structures, hydraulic structures, port structures, chemical workshops, etc. Part of the project needs to reinforce the beam section below the ground surface and contact the soil, so the steel bonding method is limited.

4) Carbon fiber sheet reinforcement can be calculated according to the calculation method of the concrete structure, so that the reinforcement effect can be guaranteed, and the calculation of the service life and reliability of the structure after reinforcement is possible.

Construction technology and application of carbon fiber sheet reinforcement construction technology

The construction process of carbon fiber sheet reinforcement is: unloading, substrate treatment, primer coating, leveling, pasting, and protection treatment.

Conclusion

This project chooses to use carbon fiber sheet reinforcement technology to reinforce the old concrete structure from the perspective of material construction technology and other aspects. Practice has proved that the interference effect on the environment and the disturbance of the old structure are very small, which fully meets the requirements of the owner. In the long run, this technology meets the requirements of modern engineering construction for construction technology, is conducive to environmental protection, and will occupy a dominant position in the field of structural reinforcement.