Electrochemical chloride extraction of a beam polluted by chlorides after 40 years in the sea

A reinforced concrete beam element, casted in 1960's while the construction of the Rance dam, has been naturally polluted by chlorides after 40 years of a marine tidal exposure. The electrochemical chloride extraction treatment (ECE) has been used in order to rehabilitate the beam. The efficiency of the ECE treatment and its durability was studied based on the analysis made before treatment, 2 months after treatment and after 17 months of immersion of the beam in a salted pond. The chloride concentration profiles show that free chlorides are extracted with an efficiency of 70 % close to the steel, 50% in the intermediate cover and 5% at the concrete surface and that there is no redistribution of the chlorides after 17 months. From the electrochemical characterizations, the steel potential values can, somehow, indicate a slow down of the rebar corrosion probability, but, this phenomenon is not confirmed by the corrosion current values. SEM and EDX results show that after the treatment, the concrete close to the steel contains less Friedel'salt and that the shape of the rust has changed