Identification of rebar corrosion induced by carbonation in cracked concrete subjected to different environmental conditions

Abstract : Reinforced concrete is a material mainly used in the construction of buildings, historical monuments as well as nuclear power plants (NPP). For different reasons, many concrete structures are subjected to unavoidable cracks that facilitate the diffusion of atmospheric carbon dioxide to the steel/concrete interface. Carbonation at the interface could induce the steel corrosion which could cause the development of new cracks in the structure and thus it is a determining factor for its durability [1][4]. Several environmental parameters may also influence the corrosion development.The objective of this work is therefore to study the effect of the existing cracks on the corrosion development in different environmental conditions (rainfall duration, relative humidity). The environmental conditions tested are representative of those surrounding the cooling towers of electricity of France (EDF) NPP. The results indicate that the corrosion development is influenced by the cracks opening. However, it was found that the corrosion is not dependent on the crack orientation (horizontal/vertical) with respect to rain. Moreover, it was deduced that the most important parameter in the corrosion development is the number of humidification/drying cycles not the rainfall duration.The result obtained will be implemented in an operational model allowing the evaluation of corrosion kinetics of the reinforcement steel in the cooling towers of EDF NPP. This model will serve to optimize the maintenance program, implemented by EDF, which aims to ensure for the cooling towers a service life over 60 years.