Microbiologically induced corrosion of concrete in sewer structures: A review of the mechanisms and phenomena

Abstract Microbiologically induced corrosion (MIC) is a century old problem facing global concrete sewer structures. Despite the substantial efforts that have been made, MIC of concrete sewers remains a highly debated subject. To further advances our understanding on the problem, we need to know the existing knowledge. In light of this, we intend to provide a state-of-the-art review on the subject. By acknowledging the complexity and broadness of the concerned problem and in order to discuss relevant aspects in depth, the scope of the current work is limited to the key elements of the mechanisms and phenomena observed on site investigations and laboratory studies for MIC of concrete sewers. In general, four main events have been considered accounting for the MIC process, i.e. formation of hydrogen sulfide in the waste steam, radiation and buildup of gaseous hydrogen sulfide, generation of sulfuric acid and deterioration of the concrete materials. Fundamentals associated with the main events, especially the important influencing factors, are reviewed and discussed. Based on site investigations and laboratory studies, several aspects of the MIC phenomena are summarized, including corrosion areas, corrosion rates, impact of cement and aggregate types. It is worth mentioning that the corrosion rates obtained on site and laboratory studies generally vary a lot, which may be attributed to different testing conditions and procedures. The fact that standard testing or evaluation methods are missing also complicates the issue. In addition, it seems difficult to establish quantitative relations between the corrosion behavior observed on site and that obtained in laboratory studies, at least based on the existing knowledge. This highlights the need for further research to advance our understanding on different aspects related to MIC of concrete sewers.