Reinforcement of Concrete Structures. Concrete Overlay Design

The use of reinforcement and repair techniques for reinforced or prestressed concrete structures is becoming increasingly common. All over the world, there are buildings for residential use, industrial activities, logistics, transport, 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. Some 85% to 90% of the world's structures have already reached a lifespan of more than 20 years, and many of them should or will have to be replaced or repaired due to their state of damage. On the other hand, mistakes may have been made during the design or construction phase, so some structures need to be reinforced or upgraded before they can be used. Lastly, changes in the use of a building or structure may require it to be modified (e.g., a significant increase in demand in the transport sector), if new requirements or changes in standards mean that the corresponding structures need to be reinforced.

When one of these situations arises, the engineer must assess whether it is more economical to reinforce the structure already built, rather than replace it. In the former case, there are a number of techniques well-suited to existing concrete structures or buildings. These include

• shotcrete ;

• different types of coatings such as :

  • carbon fibers or laminates,

  • a new layer of concrete ;

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

Among these methods, techniques for reinforcing concrete structures by embedding or adding a new layer of concrete are an interesting alternative. In fact, this method of reinforcing structures with a concrete composite section makes it possible to :

• increase the strength of deteriorated or damaged structures, or those subject to design or execution faults, in order to extend their service life;

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

It should be noted, however, that the methodology used for implementation can vary significantly: presence or absence of connectors or seam steels, quality of the rework surface, etc.

This article begins with a general introduction to the principle of repairing and reinforcing concrete structures by embedding or pouring a new layer of concrete. It also details the field of application and the...