National Highways’ A30 Chiverton to Carland Cross upgrade in Cornwall has what is said to be the “first-ever 3D-printed concrete headwall” as part of a trial of new construction methods.
Headwall structures are traditionally made from precast concrete, with lots of steel reinforcement and limited in their shape. The A30’s 3D printed curved headwall, which requires no steelwork, was installed last month by Costain as a trial on one of the wildlife tunnels being put under the new dual carriageway. (There are going to be 33 of these critter crossings along the length of the new 8.7-mile road.)
The 3D printing is part of the Digital Roads of the Future Partnership, a collaboration led by Costain with hi-tech materials specialist Versarien, the University of Cambridge and National Highways
The 2.3-tonne curved headwall is constructed using an alkali-activated cementitious material and a 3D printer.
The first trial headwall was printed at Versarien’s Gloucestershire operations centre in December. Sensors were embedded into the structure during the printing process by Cambridge University researchers to monitor temperature and movement over the coming years.
Headwalls are retaining walls built at the inlet or outlet of drainage or culvert pipes, and are installed to reduce any erosion to the pipe and surrounding area caused by water flows.
A headwall was chosen for the trial because of the ease of access for installation and monitoring, and once removed, the technology could be expanded to other areas once proved successful, National Highways said.
The project team say that the benefit of using an additive manufacturing process rather than casting in a mould is that not only does it mean no reinforcing steel but also there is more flexibility with shape – using curves instead of straight lines also saves on material costs.
Costain head of materials Bhavika Ramrakhyani said: “I feel this has brought industry and academia together to support real-life trials of emerging technologies with lots of practical challenges to mitigate.
“These trials have assisted towards undertaking further research and development towards the use of 3D concrete printing within the infrastructure industry as we need to understand the behaviour of the material and technology in real-life situations to be used for future infrastructure implementation.
“This provides a step change in the construction industry that there is no ‘one size fits all’, but different solutions are needed to combat climate change and increase productivity in parallel.”
National Highways project director Nick Simmonds-Screech said: “The headwall shows innovation and collaboration at its best and it’s exciting to be able to trial this cutting-edge technology on a major road upgrade.”
National Highways roads development director Joanna White added: “We’re committed to exploring sustainable and innovative ways of constructing and maintaining our roads and this marks a significant first step as part of the work carried out by the Roads Research Alliance.
“It’s a collective effort, we’re pleased to be partnering with the University and our supply chain and through our collaborative funding and research, we look forward to realising and delivering further initiatives within the highways industry.
“Together we are developing ideas that will improve how we design, maintain, operate and build roads as well as increase safety on our network. This is the first time National Highways has formed an alliance like this to deliver research, and we look forward to seeing the exciting results.”
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