Future asphalt surface course
The project aims to advance the use of low-carbon asphalt by building confidence in new materials through coordinated trials, testing and structured evaluation of their performance against conventional materials.
The project responds to National Highways’ commitment to achieve Net Zero for maintenance and construction by 2040. Without National Highways coordinated trials and evidence, suppliers could introduce new technologies independently, likely to causing fragmentation, delays in standardisation, and slower adoption of low‑carbon solutions. This project ensures emerging technologies are properly trialled, tested and validated, creating robust data to support standardisation and wider implementation.
The project focuses on advancing emerging low carbon asphalt technologies through trialling, testing and structured evaluation of their performance.
Work includes full-scale trials on the Strategic Road Network, laboratory testing to assess performance, monitoring of trial sites from earlier phases and knowledge transfer across industry partners.
The project is helping to advance Technology Readiness Levels and to update National Highways’ standards using real data, supporting earlier adoption and delivering long‑term benefits from proven low‑carbon materials and technologies.
Objectives
Reduce embodied carbon in asphalt materials across lifecycle stages A1–A3 (product stages – extracting raw materials, transportation, asphalt manufacturing).
Trial emerging low‑carbon technologies and evaluate their performance against conventional materials, enabling evidence‑based early adoption of the technologies on the Strategic Road Network where Technology Readiness Levels are sufficient.
Explore and trial emerging low‑carbon technologies that also improve durability, climate resilience and whole‑life performance.
Develop data‑driven updates to bring emerging low carbon technologies into The Design Manual for Roads and Bridges (DMRB) and The Manual of Contract Documents for Highway Works (MCHW) through trials, pilots and rapid performance assessments.
Advance TRL advancement of each emerging technology to establish a structured route to standardisation.
Success criteria
Demonstrated embodied‑carbon reduction in asphalt materials from lifecycle stages A1–A3 (cradle-to-gate) using primary data, carbon‑footprint calculations and Environmental Product Declarations (EPDs).
Proven performance demonstrated through laboratory testing and on‑network trials.
Technologies reaching TRL 7 or higher, supported by evidence from the programme and used to help deliver low‑carbon demonstrator projects.
Developed clear proposals for updates to DMRB and MCHW supported by trial findings and rapid‑assessment methods.
Identified whole‑life benefits by trialling emerging low-carbon technologies that also improve climate resilience and durability
How the project supports National Highways KPIs
Pavement condition improvement by trialling materials that enhance durability and reduce the need for frequent maintenance.
National Highways carbon emissions reduction through adoption of emerging lower carbon materials and technologies, including higher use of reclaimed asphalt in surface course.
Efficiency improvement by promoting durability which helps avoiding unnecessary/untimely renewals and deliver whole life benefits and operational savings.
The approach
The project delivered a structured programme of on‑network trials, laboratory testing and on‑site performance monitoring of emerging low carbon technologies. Earlier phases trial sites were assessed using National Highways’ network‑level survey data, including TRACS, SCRIM and video condition surveys.
Site trials were delivered in collaboration with the Operations Directorate, supply chain partners and industry bodies. Accelerated performance testing, carbon footprint calculations and whole‑life assessments have supported the evaluation of each technology. Knowledges based on the trials and testing from each phase were shared nationally and internationally through conferences, workshops and technical publications.
Innovative low carbon Technologies assessed to date include biobased binders, graphene‑modified asphalt, high use of reclaimed asphalt mixtures with bio‑rejuvenators, and lignin‑modified asphalts, all individually and in combinations (“stacking options”). These were prioritised based on their carbon‑reduction potential, whole‑life benefits and Technology Readiness Level.
Project obstacles and how they were addressed
Several challenges arose during delivery. Some technologies were supplier‑dependent, limiting availability. Budget constraints required trials to be integrated into OD renewal schemes, making it difficult to match the right technology with the right supplier while staying within the cost estimates. Weather was another obstacle, as first‑time asphalt trials were preferred to deliver between June and September to avoid potential risks affecting performance due to cold‑weather. Pre‑trial preparation such as pre-trial lab testing, trial design and departures from standards also required significant time frame (i.e. up to three months). Completing the project within the financial year added further pressure on timelines.
How these obstacles were addressed:
- Technology with supplier dependency, addressed through early consultation, close collaboration and clear communication with suppliers.
- Integration with OD renewal schemes, enabled through early engagement with OD asset and delivery teams to align trials with programmed works. This ensured impacts on cost, time and quality were minimised. Uplift costs for some trials were covered.
- Seasonal weather window, addressed by securing early project award to ensure site delivery within the June–September period to avoid potential impact from cold weather element specially for the first time trial of innovative technology.
- Pre-site preparation requirements, addressed through advance planning, early engagement and collaboration with the supplier to design and complete pre‑trial laboratory testing, engagement with OD delivery and asset team and proactively supporting departures from standards where needed.
- Financial year constraints for project phase completion, addressed by maintaining continuity from earlier phases and initiating activity early to manage time, quality and reporting pressures.
Outcomes and impact
The project delivered eight trial sites and 31 trial sections across five regions, progressing multiple low carbon technologies toward higher Technology Readiness Levels. The work has already demonstrated significant carbon and material re-use benefits and strengthened the evidence base data for the future standard updates. The programme has also supported national and international knowledge transfer and has received formal recognition for its contribution to decarbonising asphalt.
Key outcomes include:
- Over 180,000 kgCO₂e of carbon savings, achieved through the use of low carbon asphalt technologies as part of this work.
- More than 6,300 tonnes of reclaimed asphalt re-used, which is equivalent to approximately 15 lane kilometres of resurfacing.
- Advancement of multiple technologies toward higher TRLs, supported by full scale trials and laboratory assessments.
- Whole life benefits identified, including reduced intervention for major renewals and greater circularity through increased RA use.
- Stronger evidence base data generated for future updates to DMRB and MCHW, informed data generated from Phases 1–3.
- Sector recognition achieved, including being named award finalists, gaining ICE Carbon Champion status, and being featured in PIARC case studies, as well as selected for presentation and publication at international conferences.
User and stakeholder outcomes
Regional teams gained practical experience installing and monitoring the innovative materials across trial sites on the Strategic Road Network, building confidence in their performance under real world conditions. Supply chain partners, including pavement contractors and industry bodies, strengthened their capability through direct involvement in delivery and testing.
Low-carbon demonstrator projects were subsequently delivered through approved departures from standards, informed by evidence and learning from the trials, particularly in relation to carbon savings and performance.
Project findings were shared with local authorities, national stakeholders and international organisations through webinars, conferences, workshops and technical publications, supporting wider awareness and engagement across the pavement community.
Key insights and learning
A combination of low carbon technologies delivered greater carbon reduction and whole life benefits than applying single approaches in isolation, and the trials demonstrated that practical deployment on the Strategic Road Network is achievable. Several important lessons emerged:
- Stacking low carbon technologies delivers greater carbon reduction and whole life benefits than using single approaches.
- Laboratory testing accelerates understanding of potential performance, including durability. However, laboratory testing cannot replicate real‑world conditions, so continuous on‑site monitoring of trials is still recommended.
- Multiple trials and pilots are needed to build the evidence base data for updates to DMRB and MCHW, as standards update require repeated and consistent data.
- Carbon accounting tools and primary data are essential for assessing whole life benefits and impacts, including embodied carbon reductions.
- Knowledge‑sharing activities, such as webinars, conferences, workshops and publications, are essential for encouraging wider adoption of emerging technologies and gaining understanding across stakeholders.
Future value and next steps
The next phase will continue trialling and testing recently emerged and advanced low carbon materials and technologies. It will develop proposals for updates to DMRB and MCHW, support continued monitoring of existing trial sites and implement additional full-scale demonstrations.
Building on evidence from the trials, it will enable low carbon demonstrator projects to be delivered through approved departures from standards, supporting early adoption of emerging technologies.
This will contribute to whole life benefits and support National Highways’ commitment to achieve Net Zero for maintenance and construction by 2040.
