In carbon fiber cloth reinforcement projects, it is often encountered that multiple layers of paste are required. So the question is, how many layers of carbon fiber cloth can be pasted at most, can it be pasted infinitely?

Promise is not possible. 10.2.11 of the national standard GB52367 "Code for Design of Reinforcement of Concrete Structures" has the following provisions:

It can be seen from the national standard specification that the current requirement for multi-layer bonding of carbon cloth is that it should not exceed 4 layers, otherwise it should be reinforced with preformed plates. Although the answer is there, some of the details are worth studying and exploring in depth.

When is multi-layer paste required?

According to the definition of the national standard, carbon cloth reinforcement is suitable for the reinforcement of reinforced concrete under bending, axial compression, large eccentric compression and tension members.

The tensile strength of the first-grade carbon fiber cloth reaches more than 3400MPa. However, in some actual reinforcement projects, considering the influence of secondary force and other factors, through reinforcement design and calculation, the strength that needs to be improved exceeds 3400MPa. At this time, multi-layer carbon cloth reinforcement is required to ensure the reinforcement effect. Among the multi-layer carbon cloth reinforcement, the application of double-layer reinforcement is the most extensive, and the strength improvement is relatively stable.

How to calculate how many layers are needed?

Taking the common reinforcement calculation of normal sections of flexural members as an example, GB50367 "Code for Design of Reinforcement of Concrete Structures" has the following calculation formula:

After calculating the cross-sectional area, combined with the known conditions such as the selected carbon cloth width and single-layer thickness, the required number of layers can be calculated (cross-sectional area / carbon cloth width / single-layer thickness = number of layers).

What are the precautions for pasting multi-layer carbon cloth?

The construction process of multi-layer carbon cloth paste is generally similar to that of single-layer paste, and the specific steps are as follows:

The operation of multi-layer pasting focuses on the time interval for continuing to paste the second layer after one layer is pasted. It is necessary to wait until the dipping glue finger touches dry before proceeding to the next layer of pasting. However, this time should not be too long. If the delay exceeds 1 hour, you should wait for 12 hours before rolling the dipping glue and continue to paste it.