Work has started on the outer road deck of the Mersey Gateway's north approach viaduct with the first of over 60 concrete pours taking place.
A wing traveller machine is being used to build the outer road lanes on either side of the north approach viaduct in Widnes. It will follow the project's movable scaffold system (MSS), which is constructing the central part of the carriageway.
The wing traveller weighs 280 tonnes and is around 48 metres wide and 20 metres tall. It works in a similar way to the MSS and the form traveller machines, acting as a movable concrete mould to complete the full deck width, which, at just over 43.5 metres at its widest point, will carry six lanes of traffic.
The machine is fixed onto two railway tracks that sit on top of the deck section that has already been cast by the MSS.
Concrete is poured into both sides of the machine at the same time, enabling workers to cast 12 metre sections of the outer deck on each side of the viaduct. Once the concrete has set, hydraulic jacks push the machine forward to the next position and the cycle is repeated.
Sixty-two concrete pours are needed to create the outer deck of the north approach viaduct, while 47 pours will take place for the outer deck of the south approach viaduct. Each pour will consist of around 80m3 of concrete (40m3 each side).
Once complete, the two elevated approach viaducts will stretch across the saltmarsh on either side of the River Mersey connecting the new Mersey Gateway bridge to the main road networks in Runcorn and Widnes.
Richard Walker, project director for Merseylink Construction Joint Venture, said: "This is a significant achievement for the project. The wing traveller is yet another piece of specialist equipment that has been developed to build the approach viaducts, which will link Halton's iconic new bridge to the local towns and the wider region. This project is an immense task and one which we are on target to complete by autumn 2017."
The main structure of the north approach viaduct is expected to be complete by the end of 2016.
