The Mersey Gateway's giant bridge-building machine Webster has built the section of the approach road in Runcorn that will carry traffic across the Manchester Ship Canal and onto the new bridge.
Some 160 truckloads of concrete were poured into the 1,155 m3 mould over a 24-hour period.
Halton Borough Council is the client for the project and it awarded a 30-year contract to design, build, finance and operate the project to the Merseylink Consortium in 2014. Equity partners are Macquarie Capital Group, BBGI, and FCC Construcción. The construction joint venture is made up of Kier, Samsung C&T and FCC.
Marc Heaps, Merseylink's operations manager for the approach viaducts, said: "This was one of the more challenging pours on the project as working above the ship canal required extra planning and a change in logistics. We couldn't place the concrete pumps underneath the machine or they'd have been under water. Instead we used additional pumps on top to give us access to the concrete."
Webster measures 157 metres long, 8 metres high and 22 metres across at its widest point. It weighs 1,700 tonnes.
The steel machine was named by Halton schoolchildren after local engineer John James Webster who built the Widnes Transporter Bridge, and not after Weatherfield garage mechanic Kevin Webster as has been suggested.
Webster is accompanied on site by a wing traveller machine, which will build the outer lanes of the approach road to create the full six-lane width. The 280-tonne machine was recently lifted into place using the UK's largest crane boom.
Once complete the south approach viaduct will link the main road network in Runcorn to the new Mersey Gateway bridge.
The Mersey Gateway is one of three big river bridges under construction in the UK at the moment, along with the Queensferry Crossing across the Forth estuary and the New Wear Crossing in Sunderland.