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Foamed concrete proves crucial to bridge strengthening works – October 2011

Propump Engineering has pumped around 3000m3 of foamed concrete to strengthen and stabilise the Widford Viaduct so that weight restrictions on the A1114 London Road in Chelmsford could be lifted.

With the increase in HGV’s across the country’s bridges and viaducts, the need to strengthen and widen bridges has become paramount.

As part of a £2.73 million contract with the Highway’s Agency, contractor Edmund Nuttall Ltd worked with Propump on a solution which enabled traffic flows to be maintained over the narrow bridge during the strengthening.

Reliable, strong and lightweight, foamed concrete proved to be the vital ingredient when it came to strengthening the bridge prior to the installation of a new precast bridge deck and parapets.

Underneath the deck of the viaduct there were four longitudinal beams with further beams running across these at every three metres. This resulted in cells forming the length of the viaduct.

Foamed concrete had to be pumped in from the sides of the viaduct as opposed to going through the deck. Each cell needed to be completely filled with foamed concrete and individually vented to allow the air to escape.

This meant that a complex system of pump and vent hoses to each cell needed to be provided. Lightweight foamed concrete in a density of 1150 Kg/m3 was pumped through 300 metres of pump hoses at 56 locations along the sides of the viaduct.

Thanks to Propump the viaduct was strengthened ready for the next phase – the installation of the new precast bridge deck and parapets. Now complete, the weight restriction has been lifted and the narrow lanes removed. Vehicles over three tonnes can once again use the A1114 London Road, and there are no longer diversion routes.

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