Defects Found Under Road Surface Of Bridge On A6

Defects have been found under the road surface of a bridge on the A6 near Desborough.

Northants Highways say although structurally sound, the waterproofing has failed on the bridge deck, meaning potholes are forming.

Work is being planned to deal with the problem on the structure over the railway line, between the B576 and Braybrooke Road roundabouts, and a 40mph temporary speed limit put in place in the area in the meantime.

The bridge on the A6 near Desborough
Pic: Google

The work is due to take place over four days in May, when higher temperatures will allow it to take place.

Problems with the road surface approaching the same bridge led to the stretch of road being shut for several months in 2017.

A spokesperson for Northants Highways told HFM: “The bridge waterproofing has failed prematurely on the bridge deck.  When a waterproofing membrane fails, it debonds (lifts) from the concrete deck, which in turn means repeated vehicles travelling over the carriageway surfacing will result in potholes forming.  This is why we have put a temporary speed restriction on, so that the impact of vehicles is lessened.

“The works will consist of removing the carriageway surfacing. Removing the waterproofing membrane, a structural examination of the concrete deck and any concrete repairs carried out. The new waterproofing membrane will be sprayed onto the prepared concrete deck, allowed to cure and then tested.  If the waterproofing passes, the carriageway surfacing will be laid, followed by the road marking.

“The process is very much dictated by rain and temperature, so we have applied to have a weekend road closure in May.  We carry out waterproofing operations over weekends as once the waterproofing is removed, we cannot run vehicles over the deck. The works usually take 48 hours, working night and day.

“The works are weather dependant. If heavy rain is forecast, it will be postponed to the following weekend.  We would be looking at reviewing the forecast Thursday at midday, and making a decision then.  It isn’t work we would carry out during the colder months either, so this is why we have opted for the first weekend in May.