Efforts to curb corrosion of steel reinforcement in Battersea Power station's concrete chimneys using cathodic protection failed because large voids in the concrete obstructed the electrical current.
Cathodic protection works by passing a current through the reinforced concrete to make the steel less likely to react with salt and suffer corrosion.
But corrosion had created such large voids in the concrete of all four chimneys that a continuous circuit could not be created.
'The repairs depended on cathodic protection working, but we couldn't even locate the voids to fill them in, ' said Buro Happold associate Jim Solomon.
Demolishing the four chimneys will take a painstaking three to four months each, and is expected to start in 2006.
'The chimneys will be chipped away from the top using hand held equipment. It will be very labour intensive, ' added Solomon.
He said that the new chimneys would be rebuilt using traditional shuttering and insitu concrete to look exactly the same as the originals.