Investigation of leaching in steel fiber-reinforced shotcrete exposed to fresh and saline groundwater in a subsea road tunnel

The field and laboratory investigations performed in the Frøya subsea road tunnel, constructed between 1998 and 2000, focus on the degree of leaching undergone by steel fiber-reinforced shotcrete in fresh and saline groundwater. Shotcrete samples were extracted by core drilling at two locations: in the middle of the tunnel approximately 150 m below sea level, and near one of the portals. Leaching is only evident in the first location identified by portlandite reduction, potassium reduction, shotcrete density reduction, and suction porosity increase towards the traffic room. The leached depth is approximately 9 cm.