Comportamento a corrosione dell’acciaio in calcestruzzi con cemento a base di solfoalluminato di calcio (CSA)

Sulfoaluminate-based cements have some advantages compared to cements based on portland clinker (such as, a fast setting, high strength performance even at early curing, in addition to lower environmental impact in the production phase) that make them attractive in relation to sustainability of the construction industry. Taking into account that the pore solution of concrete with sulfoalumi-nate cement has a different alkalinity than that obtained using ordinary portland cement, the protec-tion capacity of such concrete in relation to the corrosion of embedded steel reinforcement needs to be studied. This paper describes experimental results of a study aimed at investigating the carbonation-induced corrosion of carbon steel in contact with sulfoaluminate-based concrete. Concrete with water/cement ratio equal to 0.55, made using a limestone portland cement and a sulfoaluminate cement were characterized with compressive strength, electrical resistivity and carbonation rate tests. Furthermore, electrochemical tests have been made to measure corrosion potential and corrosion rate of steel. Laboratory tests showed that pore solution of sulfoaluminate-based concrete is alkaline and induces passivation on embedded carbon steel. Once the concrete is carbonated, negligible corrosion rates were measured on embedded steel exposed up to 95% relative humidity at 20°C.