Corrosion of steel bar in carbonated concrete treated with realkalisation and inhibitor

Abstract

The combination of realkalisation and migrating corrosion inhibitor (MCI) was proposed as a protective technique for structures subjected to carbonation-induced corrosion; the effects on passivated steel bars in partly carbonated concrete were investigated. The corrosion behaviours of treated steel bars under three exposure conditions (natural indoor environment, accelerated carbonation and simulated carbonated concrete pore solution) were examined and the effects of amino-alcohol-based and amino-carboxylate-based MCIs were compared. The surface morphology of steel bars was observed by scanning electron microscopy, which indicated that MCIs could be adsorbed on the bar surfaces. Moreover, potentiodynamic polarisation curves were obtained and electrochemical impedance spectroscopy was performed. Results corresponding to a natural indoor environment and accelerated carbonation showed that current would destabilise the passivated steel bars but that the corrosion resistance of treated steel bars was significantly enhanced. According to the results in simulated carbonated concrete pore solution, the corrosion behaviour of steel bar was related to the type of MCI and the treatment parameters. Compared with amino-carboxylate-based MCI, the adsorption of amino-alcohol-based MCI was more stable although it was weakened with a decrease in pH. In general, treatment by realkalisation and MCI is more effective than simple application of realkalisation or MCI.