Reinforcement of Concrete Structures. Concrete Overlay Design

The use of techniques to reinforce and repair reinforced or prestressed concrete structures has become increasingly common. Indeed, all over the world, there are buildings used for residential purposes or for industrial, logistics, or transportation activities, as well as engineering structures, etc., that need to be reinforced or rehabilitated for a wide variety of reasons. On the one hand, their load-bearing structures, which vary greatly in quality, capacity, and function, all age and deteriorate over time. Approximately 85 to 90% of structures built worldwide have already reached a lifespan of more than 20 years, and many of them should or will need to be replaced or repaired due to their damaged condition. On the other hand, due to errors that may have been made during the design or construction phase, some structures must be reinforced or upgraded before they can be used. Finally, changes in the use of a building or structure may require modifications (e.g., a significant increase in demand in the transportation sector) if new requirements or changes in standards require the corresponding structures to be reinforced.

When one of these situations arises, the engineer must assess whether it is more economical to reinforce the existing structure rather than replace it. In the former case, there are many techniques that are well suited to existing concrete structures or buildings. These include, for example:

• shotcrete;

• different types of coatings such as:

  • carbon fibers or strips,

  • a new layer of concrete added;

• prestressing cables arranged outside the structure, i.e., additional prestressing by post-tensioning.

Among these methods, techniques for reinforcing concrete structures by coating or adding a new layer of concrete are therefore an attractive alternative. This process of reinforcing structures with concrete sections offers the following advantages:

• to increase the strength of structures that are degraded, damaged, or subject to design or construction defects in order to extend their useful life;

• to adapt the structure to changes in its operating conditions (change of use) or to increase its load-bearing capacity.

However, it should be noted that the methodology used for implementation can vary significantly: presence or absence of connectors or seam steel, quality of the repair surface, etc.

First, this article provides a general overview of the principle of repairing and reinforcing concrete structures by coating...