Chloride induced corrosion of steel reinforcement in alkali activated slag concretes: A critical review

Alkali activated materials (AAMs) have been recognised as potential alternatives to Portland cement concretes in specific applications in the construction industry due to their environmental benefits such as substantially reduced CO2 emissions and utilisation of industrial wastes. While many studies reported the superior performance of AAM concretes over Portland cement concretes in protecting steel from corrosion, some other studies indicated an opposite view. Hence, there is a need for further research on the long-term corrosion studies of AAM concretes in the laboratory as well as in the field. Among many important areas of investigation is the resistance of AAMs to chloride induced corrosion of steel reinforcement which is not well understood. In this paper, the above aspect is reviewed including chloride ingress, chloride binding and chloride induced corrosion rate of steel reinforcement in AAMs. Chloride ingress in AAMs involves both open and closed pore systems. Chloride binding in AAMs is predominantly physical and not chemical. The chloride threshold levels initiating steel corrosion in AAMs are significantly different in comparison to Portland cement concretes.