Hankinson Painting Group’s work on Silver Jubilee Bridge, Runcorn is now in line for further recognition. Having already been selected in 2009 as the Painting Decorating Association Industrial Painting Contract of the Year, the contract has now been shortlisted for a conservation award in the British Construction Industry Awards 2010 for the cathodic protection work.
The new approach to cathodic protection has detained corrosion in the deck of the bridge extending its life from an estimated 5-10 years to 25 years and beyond. The solution has averted the enormous disruption, cost and environmental impact of replacing the bridge deck on this major regional transport link.
The bridge deck is reinforced concrete supported on structural steelwork. Though the original surfacing provided some waterproofing, it quickly degraded and when the surfacing was replaced a decade ago the deck was found to be heavily chloride contaminated and badly corroded.
The option chosen for tackling chloride contamination in the structure was to use cathodic protection (CP) where a low voltage current is passed from an inert anode to the reinforcing steel. This stops corrosion. CP has been used to protect concrete in the UK since the late 1980’s because it cuts down the amount of concrete repair required and so saves money, materials and carbon dioxide. CP systems come with remote monitoring so future maintenance and inspection is simplified.
Traditional anode systems involve either a mesh in a sprayed concrete overlay fixed to the deck soffitt or discrete anodes drilled on to the deck. On the Silver Jubilee Bridge difficult access would make sprayed concrete hard to apply while traffic induced vibrations in the deck would risk it delaminating in the future. Drilling was not an option due to the thickness of the deck. A system was therefore developed by system designer Mott McDonald whereby anodes sat in foam filled glass reinforced polymer trays (“cassettes”) which were bolted to jetty soffits and could be installed quickly and simply. To provide electrical connectivity between the anode and reinforcing steel the foam had to be wet so a hydrophilic gel was placed in the tray around the anode. The works were carried out from a full scaffold that had been erected to enable painting.
Effective completion of the project was marked in October 2009 following a 12 month trial of the CP system. Physical inspection supported data from remote monitoring showing that degradation had been fully arrested. The system has proved successful.
This innovative CP system can potentially be used on chloride contaminated structures worldwide, offering infrastructure owners and operators huge cost savings and delivering major social economic and environmental benefits.
Judging takes place on site on 6th July and winners will be announced at an awards ceremony in London on 13th October.
The British Construction Industry Awards focus on client satisfaction and all round excellence in the delivery of projects and their benefits.
More information can be found by visiting www.emap.com
14.06.10