Corrosion Resistance of Steel Fibre Reinforced Tunnels Subject to Stray Current

Steel fibre reinforcement is convenient for use in many tunnels and has many advantages over conventional steel reinforcement. However, for electrified railway tunnels there is a risk of stray current-induced corrosion attack which needs to be assessed. If the discontinuous steel fibres can transmit stray currents, then this is problematic as it will result in corrosion and ultimately degradation of the tunnel lining, this has raised concerns over its application. In the UK alone, the cost of repair and rehabilitation of transportation infrastructure is 600 million pounds per year. The reduction in the electric potential for stray current induced corrosion forms an important part of the design process. Experimentation on fibre reinforced concrete subject to alternating current indicates that steel fibre reinforced concrete is resistant to corrosion, due to the development of an electrical double layer on the steel surface. However, the presence of only 2% by mass of chloride (0.3 mol/L) is sufficient to reduce this corrosion resistance, weakening the tunnel lining. This indicates that where anions such as chloride are not present, it may be possible to use steel fiber reinforced concrete for railway tunnel linings.