When corrosion was found in the deck of Runcorn’s Silver Jubilee Bridge, the council was faced with two difficult options.
The deck is made of reinforced concrete supported on structural steelwork. Chloride contamination had caused the corrosion, and one option was to remove all of the contaminated concrete: a hugely disruptive and inefficient procedure. The other option was to use cathodic protection, where a low voltage current is passed from an inert anode to the reinforcing steel. But the deck wasn’t thick enough to drill the anodes into.
The solution was inspired by a system used on harbour jetties in Norway. The anodes sit in a foam-filled polymer tray, and are bolted on. They need to be wet for electrical connectivity: easy on a jetty, less so on a bridge. So a hydrophilic gel was placed around the anode, ensuring the moisture and connectivity.
Inspections have shown that this innovative approach worked, and the degradation has been fully halted. The system has the potential to be applied to chloride contaminated infrastructure all over the world, with great social, economic and environmental benefits.
"A ground-breaking, low-cost solution to corrosion caused by chloride contamination."