Corrosion of reinforcements in concrete – Management of ageing structures

Corrosion of reinforcement in concrete is taken into consideration for all structures, whether in the design stage or in service. This article deals with the management of existing structures, which are ageing and may be affected by reinforcement corrosion. This management mainly concerns technical maintenance, but the methodological (choice of actions to be taken, etc.) and financial aspects will also be discussed.

As the structure ages, and disorders appear, the client is faced with the question of how to maintain its structural integrity. Well-conducted diagnostics can pinpoint the origin of disorders, their type and probable evolution. Additional studies, mainly of a mechanical nature, clarify the impact of these disorders on the mechanical stability and safety of the structure. A decision must then be taken as to the nature and location of the actions required, especially repairs. The steps involved in this decision-making process are detailed in this article, using two examples: the case of bridges and viaducts, where corrosion is mainly triggered by chlorides (marine environment and/or de-icing salts), and the case of power plant cooling towers, which are affected by carbonation.

Surveillance of ageing structures is also described (visits, inspections, monitoring), and the elements required for decision-making on repairs are prioritized. The main constraints relating to works, their cost, implementation and necessary controls are also specified, as are the principles of warranties.