Biofilm Threatens Concrete Integrity in Subsea Tunnels: Rapid Degradation Unveiled

A recent study by Chalmers University of Technology in Sweden reveals a concerning phenomenon: biofilm formation in subsea road tunnels is rapidly degrading concrete. The research, focusing on the Oslofjord tunnel in Norway since 2014, indicates that bacteria carried by penetrating seawater are consuming the concrete at a rate of up to one centimeter per year. This biocorrosion process, driven by bacteria metabolizing iron, manganese, sulfur, and nitrogen, weakens the concrete structure, potentially leading to costly repairs and safety hazards. Associate Professor Frank Persson notes, "Where there is saltwater intrusion, a biofilm will form, and the concrete covered by the biofilm will gradually dissolve." The study highlights that while new concrete has a high pH, natural chemical degradation lowers it over time, creating a more hospitable environment for bacteria. This interaction accelerates the corrosion of the concrete reinforcement and the concrete itself. Professor Britt-Marie Wilén emphasizes the need for continuous monitoring, stating, "This type of biofilm is a pretty clear warning signal. You need to monitor the water flow and the spread of the biofilm and locate loose and damaged concrete to spray again, if necessary." Researchers recommend regular pH measurements of the concrete, examination of groundwater flow, and monitoring of biofilm spread. The findings also suggest that climate change, with warmer ocean temperatures and lower pH values, could exacerbate the corrosion rate. The study also led to the discovery of a new family of anammox bacteria, Anammoxibacteraceae, providing new insights into nitrogen metabolism.