Why Concrete in Road Tunnels Decomposes Unexpectedly Fast: Research

When seawater penetrates concrete in road tunnels, a biofilm is formed that breaks down the concrete. This can lead to high costs and the risk of damage if stone and concrete drop from the tunnel roof. In a new study, carried out in the Oslofjord tunnel in Norway by a team of researchers at Chalmers University of Technology in Sweden, research reveals the mechanisms behind the degradation, and its unexpectedly rapid progression.

Penetrating seawater carries bacteria that form colonies – biofilm. The bacteria attack the concrete that is supposed to prevent stones from loosening from the tunnel walls. The concrete becomes porous and risks breaking apart. The biofilm gets its distinctive colour from rusting reinforcement in the shotcrete.
Banner image credit: Chalmers University of Technology I Britt-Marie Wilén