National Highways trialling innovative low-carbon asphalt with PMB bio-binders on A30 in Devon
HANSON have used an innovative low-carbon asphalt to resurface the A30 Cutteridge to Alphington eastbound scheme near Exeter in Devon. The work is part of the company’s pavement category management framework agreement with National Highways.
It is the first time Hanson have trialled their CarbonLock asphalt containing polymer-modified bitumen (PMB) bio-binders on the strategic road network in partnership with National Highways.
Two trials are being carried out. The first trial includes Nynas’s biogenic binder Nypol RE and the second trial uses the same asphalt mixture but includes Shell’s new bio-component binder Cariphalte CarbonSink.
Both asphalts were produced at Hanson’s Hingston Down plant and laid by Hanson Contracting. Each trial comprised a 40mm thickness surface course with 53PSV aggregates for around 500m of both lanes of the eastbound carriageway.
Natural biogenic material absorbs and stores CO2, which is then ‘locked’ into the bio-component binders (bio-binders) and not released back into the atmosphere, even when the asphalt is recycled.
In addition, the PMB binder used in both trials is expected to enhance durability and further extend the life of the asphalt, thus reducing the frequency of maintenance interventions.
Adrian Hadley, technical head (asphalt and aggregate) at Hanson UK, said: ‘We are committed to working with our clients to help them meet their net-zero objectives and these trials are an excellent example of this.’
The work was co-ordinated by Atkins as part of the National Highways research project ‘Future Asphalt Surface Course Linking to NH Net Zero’ under SPaTS 2. The performance of the two trial sections will be closely monitored to see how they compare with ‘standard’ PMB asphalt used elsewhere on the project.
An assessor from the British Board of Agrément (BBA) was in attendance when the asphalt was laid, and the material is now undergoing a programme of in-house testing and monitoring with the intention of it being included within Hanson’s BBA HAPAS certified products.
Umesh Parajuli of the pavements team in the Safety Engineering and Standards Division of National Highways, said: ‘These trials are part of our feasibility study and whole-life benefits analysis of emerging low-carbon technologies, which will help us meet our 2040 net-zero carbon deadline for construction and maintenance activities.
‘National Highways, in partnership with Atkins, will monitor the performance of both sections and use the results of extensive laboratory testing carried out at Nottingham University to review whole-life carbon reduction with asphalt surfacing.
‘We hope this trial containing PMB bio-binders will help to bring innovative technology into our specification.’