Kier Highways has taken reduce, reuse, recycle to the next level by repurposing 3.5 miles of dual carriageway on the National Highways Strategic Road Network (SRN) for reconstruction works in Warwickshire.

Instead of going to a landfill, some 17,432 tons of material from layers of old road surface have been reused and are now a part of a much smoother, safer A46 Warwick Bypass.

By recycling more than half of the materials used in the original stretch of road, the contractor has cut the scheme’s carbon footprint by 23%. The remaining materials have also been recycled across the SRN through other projects.

Kier Highways led the project on behalf of client, National Highways, and recruited Aggregate Industries (AI) to carry out the resurfacing on the northbound carriageway between Sherbourne roundabout and the Leek Wootton roundabout.

The original stretch of the busy road deteriorated to a point where, following a number of temporary repairs to ensure safety, a full depth reconstruction was needed - digging as deep as 15 inches to replace the layers of road surface.

Much of the material in the lower levels contained tar which is classed as carcinogenic- has the potential to cause cancer - and is normally dealt as hazardous waste and disposed of at a licenced waste processing facility.

However, tar-bound material can be safely recycled and encapsulated back into the pavement layers through processing and re-mixing.

Kier Highways and AI devised a low carbon pavement solution and discovered that the greenest and most cost-effective way to do this was by recycling the existing carriageway material and reducing the amount that would have to go to landfill.

The old layers of road were recycled back into the new carriageway using AI’s ex situ cold recycled Foamix asphalt.

This colder mixed material can be handled and compacted at a much safer ambient temperature and reduces the asphalt fumes on site which workers are exposed to during the resurfacing. The material was mixed on site to minimise vehicle movements, reducing the scheme’s carbon footprint even further.

Using recycled materials also meant there was less raw material needed for the works, meaning around 82,000 road miles were saved on the scheme which ran between late July and September 2021.

Scott Cooper, managing director, Strategic Highways at Kier Highways, said: “This is the first time that Foamix has been used on this type of road and this work on the A46 scheme really demonstrates how innovation and excellent collaboration across the value chain is needed if Kier and our partners are to succeed with reaching our net-zero ambition and combatting climate change.”

Zero waste, zero carbon and health, safety and wellbeing are some of the key principles laid out in Kier Highways 2020-2025 sustainability strategy and One Planet Action Plan (OPAP), Driving for a Sustainable World. This strategy is aligned to Kier’s sustainability framework, Building for a Sustainable World.

Kier plans to produce no avoidable waste by 2035 and achieve net-zero carbon across their operations and supply chain by 2045.

National Highways project manager, Ryan Davies, said: “We have committed, through our net zero carbon plan, to rapidly cut carbon from road construction, maintenance and operations, and support the transition to zero emission vehicles. 

“A vital part of meeting our ambitious objectives is having the support of our supply chain on schemes such as this. Through close collaboration with partners such as Kier and AI we are taking great strides on our journey to net zero carbon.”

AI’s national technical manager, Neil Leake, said: “Good collaboration and an innovative approach were at the heart of this scheme, with people working together to achieve the same low carbon goal. We had some significant challenges to overcome to make sure this scheme could be delivered on time and still meet the low carbon goal we set ourselves.”