Have you paid attention to the influence of the substrate on the structural reinforcement?

1. Restriction of the substrate on the reinforcement method

2. Influence of substrate strength on structural reinforcement

Restriction of the substrate on the reinforcement method

In the reinforcement of concrete structures, most reinforcement methods have minimum requirements for the strength of the substrate. The enlarged section reinforcement method is suitable for the reinforcement of flexural and compressive members, but it is necessary to conduct on-site inspection and determine that the original member concrete strength level is not lower than C13. The construction of sticky steel reinforcement and carbon fiber cloth reinforcement for easy construction requires that the field measured strength level is not lower than C15. The winding reinforcement method should not be lower than C10. The prestressed carbon fiber reinforcement method is not less than C25. Reinforcement methods have requirements on the strength of the substrate.

It can be seen from this that the strength of the substrate is an important limitation for the selection of the reinforcement method, and attention should be paid to the reinforcement. The reason why there is a constraint on the strength of the substrate is mainly considering the following factors.

Influence of low strength of substrate on structural reinforcement

First of all, the strength of the base material is directly related to the increase of the bearing capacity after reinforcement.

For example, in the reinforcement of carbon fiber cloth, if the strength of the substrate is too low, it may cause the concrete substrate to crack or crush the upper part due to insufficient strength, but the carbon fiber cloth has not yet fully strength. In the reinforcement of the enlarged section, if the strength of the base material is too low, it is difficult to ensure that the newly poured concrete and the base material can work together, which easily causes the separation of the new and old concrete and reduces the bearing capacity.

For the construction method using adhesives and reinforcement materials, the strength of the substrate is also related to the adhesive bonding effect.

When the steel structure with carbon steel or carbon fiber cloth is used to reinforce the concrete structure lower than the specified strength, the bonding strength between the base material and the steel plate or carbon fiber cloth will be low. As the load increases, peeling damage is likely to occur. Peeling damage will cause the reinforcement material to separate from the substrate until the reinforcement fails. Peeling damage is dangerous and brittle and should be avoided during structural reinforcement.

In addition, when there are cracks on the surface of the substrate, or the presence of honeycombs, voids, etc. leads to poor integrity of the concrete substrate and low surface strength, it will also adversely affect the reinforcement effect. Before the reinforcement, crack glue and sealing glue can be used to repair the cracks, remove the diseased concrete, and use the leveling glue to perform defect treatment to make the concrete substrate strength meet the requirements, and then carry out subsequent construction to ensure the reinforcement effect.