New Anglo Irish Bank building left exposed to the weather

By The Helpful Engineer / On / In Technical & Discussion

Construction work on the new 260,000 sq ft Anglo Irish Bank headquarters ceased in May 2009 and has not resumed. The completed building frame lies exposed to the weather, which will speed the corrosion of the frame. The building work was stopped in 2009 as it was the subject of a successful legal challenge from rival developer Sean Dunne, who claimed that the DDDA should not have certified the office block as being exempt from planning permission in July 2007. See photograph below:

View of unfinished new Anglo Irish Bank HQ

The new Anglo Irish Bank headquarters building is exposed to the weather in a way its designers did not intend as they had no idea that it would stand for years without protective walls and heating in place. The building frame is reinforced concrete and this is susceptible to corrosion if the depth of protection chosen is not sufficient for the exposure conditions the concrete actually experiences. The site is on the tidal part of the river Liffey and is 3 km from open sea, therefore the surrounding air is rich in salt which speeds the corrosion of concrete. If the concrete frame is to be left exposed for much longer before work recommences, carbonation testing of the concrete would need to be carried out.

Preventative action

The protection to the steel reinforcing bars in the building should be above 35mm in depth as the frame is exposed to the elements. Where reinforced concrete is protected against the weather, the cover depth can be as low as 20 to 30mm deep, whereas concrete exposed to weather would be required to have a cover depth of between 35 to 50mm. The concrete strength, cement content and size of the steel bars also have an impact on the cover depth selected. The cover depth would never be less than 20mm as this is a minimum required for fire protection of the steelwork and to allow the concrete to bond with the steel and transfer stress. A possible temporary solution for Anglo Irish Bank to this issue would be to protects the concrete frame by either spraying on a concrete sealer or installing a cost effective weather proof fabric cladding around the building.

See more on the mechanics of concrete corrosion in the ‘carbonation of concrete’ article on this website.

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