Application of electrochemical methods for studying steel corrosion in alkali‐activated materials

• Published in: Materials and corrosion 2023-07, Vol.74 (7), p.988-1008
• Main Authors: Mundra, Shishir, Samson, Gabriel, Masi, Giulia, Achenbach, Rebecca, Bastidas, David M., Bernal, Susan A., Bignozzi, Maria C., Criado, Maria, Cyr, Martin, Gartner, Nina, Greve‐Dierfeld, Stefanie, Legat, Andraž, Nikoonasab, Ali, Provis, John L., Raupach, Michael, Gluth, Gregor J. G.
• Format: Article
• Language: English
• Subjects: alkali‐activated materials; Anodic polarization; anodic/cathodic polarisation; Blast furnace slags; Cement; Circuits; Civil Engineering; Concrete; Corrosion; Corrosion resistance; Corrosion tests; Electrode polarization; Engineering Sciences; linear polarisation resistance; open circuit potential; Portland cements; reinforcement corrosion; Reinforcing steels; resistivity
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.202313743

Alkali‐activated materials (AAMs) are binders that can complement and partially substitute the current use of conventional cement. However, the present knowledge about how AAMs protect steel reinforcement in concrete elements is incomplete, and uncertainties exist regarding the application of electrochemical methods to investigate this issue. The present review by EFC WP11‐Task Force ‘Corrosion of steel in alkali‐activated materials’ demonstrates that important differences exist between AAMs and Portland cement, and between different classes of AAMs, which are mainly caused by differing pore solution compositions, and which affect the outcomes of electrochemical measurements. The high sulfide concentrations in blast furnace slag‐based AAMs lead to distinct anodic polarisation curves, unusually low open circuit potentials, and low polarisation resistances, which might be incorrectly interpreted as indicating active corrosion of steel reinforcement. No systematic study of the influence of the steel–concrete interface on the susceptibility of steel to corrosion in AAMs is available. Less common electrochemical methods present an opportunity for future progress in the field. Studies on the corrosion of steel reinforcement in alkali‐activated materials (AAMs) are reviewed. It is demonstrated that important differences exist between steel corrosion in AAMs and conventional cement, and between different classes of AAMs, which affect the outcomes and the interpretation of electrochemical measurements.