Modifications of corrosion products during galvanic treatment of reinforced carbonated concrete
Résumé
Application of a cathodic current on a rebar in concrete is often used to produce (consume) hydroxyl anions (hydronium cations) in order to rise up the pH of carbonated concrete. Corrosion products around the rebars can be modified by the treatment. One way to assess the efficiency of this rehabilitation process is to analyze the corrosion products before and after treatment. However iron II compounds are highly sensitive to aerial oxidation. An in-situ Raman study has been undertaken, on a specially designed steel rebar embedded in concrete without direct contact with the electrolytic solution. As a first step an anodic current has been imposed in order to create a corrosion layer at the concrete steel interface. Green Rust (iron II, III hydroxide) formation has been analyzed as expected. Then the current has been turned in the cathodic range. Two processes occur simultaneously, within one or two days of polarization at 1A/m2: Green Rust is converted into magnetite (Fe3O4) and reduced into brucite (Fe(OH)2). The original setup will be presented, together with the results and their consequences on rebar corrosion process.