HS2 decreases carbon emissions in key viaducts by up to 66%

This has been achieved by using 'double composite' structures which use less concrete and steel.

The news comes as engineers at Westbury, on the Oxfordshire and Buckinghamshire border, were installing the second viaduct deck.

This design change followed the early success of HS2’s first double composite viaduct at Wendover Dean.

Wendover Dean Viaduct (Image: HS2)

The new method draws on experiences from high-speed rail projects across Europe.

Unlike traditional single composite structures, where steel beams support a reinforced concrete deck, the double composite design adds a concrete bottom, drastically reducing the overall amount of concrete and steel used.

The production of steel and concrete is a significant contributor to carbon emissions in construction.

This move allowed the team to reduce the embedded carbon in the five viaducts - Westbury, Turweston, Wendover, Small Dean and Lower Thorpe - by between 52 and 66 per cent.

Westbury Viaduct (Image: HS2)

HS2's head of civil structures, Tomas Garcia, said: "HS2 will improve journeys between Britain’s two biggest cities while freeing up more space on the most overcrowded parts of the existing mainline for more local services.

“The double composite approach – which combines the strength of steel in tension and with concrete in compression – has huge potential to cut carbon in construction by enabling more efficient bridges.

"I look forward to seeing them completed and hope the lessons we have learnt can be successfully applied to other bridge projects across the UK."

One of the viaducts at Brackley is currently having its 320-metre-long double composite deck positioned.

Work taking place during the Westbury Viaduct deck slide (Image: HS2)

The viaduct is part of HS2’s project to better connect London, Birmingham and the North, with the potential to provide more train services on the busy southern end of the West Coast Main Line into London Euston.

Changes in the bridge's craftsmanship, including the use of low-carbon concrete and steel along with alternative foundations, helped the design panel cut the viaduct’s embedded carbon by 60 per cent.

EKFB, made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall, is delivering civil engineering work on 80km of HS2.

Jose Candel, EKFB’s design delivery director, said: "The double composite design of this group of viaducts spanning Bucks and Northants is exemplary here in the UK.

"This industry-leading approach is innovating and paving the way for future infrastructure projects which will not only benefit on-site construction but supports EKFB's drive to reduce a huge amount of carbon in the process."

The weight of the deck increases with each push - from an initial 1,145 tonnes this week to an expected 2,695 tonnes by year end - as it is constructed in three sections.