A practical approach to decarbonising road reinstatement: A47 Acle Straight

Project case study

Project description
National Highways has carried out a low carbon exemplar project in the East of England in partnership with WSP and Heidelberg Materials UK.

Ten miles of the A47 Acle Straight (Acle to Beccles Interchange) near Great Yarmouth in Norfolk has been resurfaced using a range of carbon reduction measures including foamed asphalt, high levels of recycling and the use of electric plant.

Due to the geology of the area, suitable aggregates are scarce and therefore not readily available for asphalt production. While traditional asphalt mixes permit some recycled content, primary material is still needed to be imported by road or rail, increasing emissions and the carbon footprint of works.

The original specification for the binder course for the ten-mile stretch of single carriageway was 100mm SMA20 PMB, which would typically contain 10 per cent reclaimed asphalt. However, Heidelberg Materials suggested replacing this with 150mm of evoBuild foamed asphalt, which is produced using mobile recycling plant located close to site and allows over 90 per cent recycled content.

“The scheme is a great example of supply chain collaboration in action,” said Scott Cooper, Managing Director of Contracting at Heidelberg Materials UK.

“We worked with National Highways and scheme designer WSP to make the case for using evoBuild foamed asphalt for the binder course. It is a cold recycled bound material (CRBM) manufactured by injecting water and air into hot bitumen under high pressure. It allows the re-use of the existing road and is produced at a lower temperature, resulting in significant carbon savings.”

Mix design trials
Core samples were taken from the existing road and incorporated into the trial mix, to test the recyclability of the material and replicate the live scheme. The samples were found to include tar bound material, which is classified as hazardous waste requiring specialist disposal at an approved landfill site. However, this type of material can be incorporated into evoBuild foamed asphalt, resulting in a further benefit of the revised design.

A full 150mm evoBuild foamed asphalt binder course was laid and tested at Heidelberg Materials’ Shap quarry in Cumbria, where its mobile cold mix recycling plant was located at the time, ensuring the proposed mix design achieved the required compaction, strength and quality of finish.

As a result of the success of the trial, a departure in the specification was obtained, allowing the planned 100mm SMA binder to be replaced with 150mm CRBM. The mix design included 93 per cent recycled materials – 82 per cent reclaimed asphalt recovered from the A47, which included approximately 2,400 tonnes of tar bound material, plus 11 per cent Pulverised Fuel Ash (PFA), a by-product of coal-fired power generation.

In total the scheme used 14,500 tonnes of evoBuild foamed asphalt, 1,800 tonnes of which were produced using a biogenic bitumen binder, which reduced the carbon emissions associated with this material by a further 20 per cent.

The 14,500 tonnes of evoBuild foamed asphalt produced for the project included 13,485 tonnes of recycled material – 11 times more than the original binder course specification, which would only have included 1,080 tonnes of recycled material.

Foamed asphalt production
During the resurfacing work, the existing asphalt road surface was removed to a depth of 190mm and the planings taken to Heidelberg Materials’ compound located eight miles away from the site. This location, significantly closer than the nearest asphalt plant which is 24 miles away, minimised vehicle movements and their associated emissions.

The company used its high-performance Wirtgen KMA 240i cold mixing plant to produce the evoBuild foamed asphalt. The material offers a lower carbon alternative for base and binder course applications is designed and manufactured in accordance with ISO 9001 and is compliant with SHW cl948 (now CC 202) and BS 9228:2021.

“evoBuild foamed asphalt was the perfect solution for this scheme,” said Scott.

“It allowed the road planings to be processed and recycled back into the new binder course and minimised vehicle movements by backhauling the planings taken to the compound with new material being laid on site. This reduced the number of unladen trips and associated carbon emissions, and improved efficiency.

“As it is a cold process, its production requires significantly less energy compared with hot mix asphalt. Overall, it resulted in an A1-A4 material-level carbon reduction of approximately 55 per cent, with evoBuild foamed asphalt generating 34.8kg CO₂e per tonne, compared to 76.6kg CO₂e per tonne for the original SMA20 PMB specified.

“When considered across the entire scheme, the cumulative effect represents a substantial carbon saving of approximately 400 tonnes of CO₂e and a dramatic increase in recycled content, making the A47 Acle Straight project an excellent example of sustainable highway construction in practice.”

The evoBuild foamed asphalt was sampled at both the plant and the paver and tested for particle size distribution and strength performance, both in the laboratory and in situ, to ensure consistent quality and uniformity throughout production and placement. The material was laid using a high-compaction tracked paver to achieve a dense, well-compacted layer and a high-quality finished surface.

Going electric
The project also trialled the use of electrified plant machinery such as pavers and rollers to assess the limitations of this equipment and their carbon saving potential.

As part of this, Ammann supplied the eABG4820 paver to be trialled for the first time in the UK. It is the largest electric paver on the market (2.5-5 metres) and can cut the carbon emissions associated with road laying by 70 per cent.

A Dynapac SD1800We all electric midi paver was also used to lay the conventional warm mix surface course asphalt, which was supplied from the nearest plant. Two electric rollers and an electric welfare van completed the plant used on the project.

“The extensive use of electrified plant demonstrated what the future of road laying could look like,” said Scott.

“The performance of the rollers and pavers was excellent. The rollers provided two shifts from one battery charge and the pavers more than one. The biggest challenge with electric equipment is always being able to recharge the batteries on site, and this was overcome by using a charging trailer.”

National Highways is the first organisation of its type to achieve PAS 2080 accreditation for its carbon accounting – a standard Heidelberg Materials has also reached. The A47 scheme was completed to meet that standard for carbon management in infrastructure, in line with National Highways’ ambitions to finding new low carbon ways to maintain its road network.

“National Highways has ambitious plans, backed by science, to decarbonise our core business by 2030; to achieve net zero across our supply chain by 2040; and to achieve net zero across our whole network by 2050”, said Angela Halliwell, Head of Carbon and Environmental Sustainability Strategy and Planning at National Highways.

“Asphalt is one of our key materials we use at National Highways, and it is used for road surfacing on over 96 per cent of our network. Our Net Zero plan identifies asphalt as contributing 15 per cent to our total construction and maintenance emissions.

“Together with our supply chain partners, we’re taking positive steps towards a more sustainable future. As part of that, we’ve created 10 asks specifically for designers on our schemes, laying out the 10 things our contractors can do today to cut carbon.

“We hope carbon exemplar projects such as this one on the A47 in Norfolk will pave the way for industry-wide changes, resulting in significant carbon savings, improved roads for drivers, and quieter roadworks for our neighbours.”

Dermott Doyle, Technical Director at WSP, added: “At WSP, delivering infrastructure that combines operational excellence with a low carbon impact is a core priority. On the A47 project, we collaborated closely with National Highways and Heidelberg Materials to design a major pavement intervention that maximises recycled content and reduces carbon emissions. This project demonstrates how sustainable practices can be embedded into everyday road construction, while also reflecting the specific context and operational requirements of this site.”

Key facts and figures:
•    A projected carbon saving exceeding 400 tonnes of CO₂e.
•    Increasing the use of recycled materials by more than 13,500 tonnes.
•    Providing a textbook example of the circular economy in practice each shift.
•    Recycling 2,400 tonnes of tar-bound material, preventing its disposal in specialist landfill sites.
•    Eliminating the need for virgin aggregate in large volumes, especially critical in a region with limited local geological availability.
•    Cold mix recycling plant situated close to site (8 miles away) reducing transport distances and associated carbon (16 miles closer than asphalt supply plant).
•    Work was carried out overnight between May and November 2025.

Low carbon construction
This year, National Highways established a Low Carbon Demonstrator Fund to help successfully trialled products take the next step towards becoming a standard option for resurfacing schemes.

The fund is enabling projects across the country to take opportunities with the new low carbon technologies and helping suppliers to make a sustainable transition toward using them as a new business as usual.

The A47 Acle Straight was selected as a carbon exemplar project because it is located in a region where suitable aggregates are scarce and not readily available for asphalt production. Using traditional construction methods would have required importing large quantities of aggregate from distant sources, resulting in significant carbon emissions and increased heavy vehicle movements.

By selecting this scheme as a carbon exemplar, a mobile recycling plant was brought close to the site, drastically reducing transport requirements. The project placed a strong focus on maximising the use of recycled materials, minimising the need for new virgin aggregates, and therefore reducing the overall carbon footprint.

In addition, the A47 Acle Straight scheme provided an excellent opportunity to demonstrate the effectiveness of CRBM (evoBuild foamed asphalt). This process allows for the recycled layer to be overlaid with a surface course and reopened to traffic within a single night shift, showcasing both environmental and operational efficiency.

The project is partially funded as a low carbon concrete technology demonstrator through Innovate UK. Innovate UK is the UK’s national innovation agency supporting business-led innovation in all sectors, technologies and UK regions. It is a non-departmental public body operating at arm's length from the Government as part of the UK Research and Innovation.

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