Trials of ‘biogenic asphalts’ gather pace

Trials of ‘biogenic asphalts’ are becoming more widespread as the industry looks to offer lower carbon solutions to help reach the Government’s net zero carbon ambitions.

These products contain natural biogenic materials which absorb and store CO2 throughout their first life. This is then ‘locked’ within the binder in the asphalt mixture and not released back into the atmosphere, even when the asphalt is recycled.

When Birmingham City Council and its principal contractor, Kier, were looking at ways of reducing carbon emissions as part of scheduled work to resurface the A452 Chester Road, it was the perfect opportunity to trial ‘biogenic asphalt’.

As part of an alliance framework, monthly sustainability forums were held involving all supply partners, to encourage innovation and more sustainable solutions.

“There was a strong will from all parties to lower the operational carbon footprint,” explains Brian Kent, National Technical Director at Tarmac.

“Given the high traffic volumes and importance of this route, a key part of the challenge was to reassure the client that the proposed solution would deliver the same performance as a more conventional asphalt with no compromise in long-term performance.”

In all, 530 tonnes of Tarmac’s biogenic asphalt was laid as the binder course, saving 6.5kg CO2e per tonne of asphalt or 3.45 tonnes of CO2e in total.

National Highways has also formally trialled asphalt containing a polymer modified bitumen (PMB) bio-binder on the strategic network for the first time.

Hanson has used its CarbonLock product to resurface the A30 Cutteridge to Alphington eastbound scheme near Exeter, Devon, as part of its pavement category management framework agreement with National Highways.

Two trials were carried out: the first 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 and each trial comprised of a 40mm thickness surface course with 53 PSV aggregates for around 500 metres of both lanes of the eastbound carriageway.

In addition to the biogenic material in it effectively acting as a carbon sink, 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.

The work was coordinated by Atkins as part of the National Highways SPaTS 2 (Special Professional and Technical Services) research project Future Asphalt Surface Course Linking to NH Net Zero. 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.

North of the border, Breedon and Nynas have also used asphalt containing biogenic components on the Scottish network for the first time.

The move follows successful trials in England and the product used is part of the Breedon Balance range of materials which also contains Nynas’s Nypol RE. The asphalt complies with the Transport Scotland TS2010 specification, and was laid on the A92 in the north east by Amey, network contractor for the region. The trial aligns with Transport Scotland’s aim of reducing carbon emissions by 75% by 2030.

Council’s low carbon solutions to achieve net zero by 2045

Leicestershire County Council has pledged to become a carbon neutral council by 2030 and to achieve net zero across the county by 2045 – five years ahead of the Government target.

Working with main contractor Aggregate Industries, its highways teams have been trialling the use of recycled and low carbon products in its bypass improvement schemes on the A426 at Blaby, the A6 at Market Harborough and the A47 at Hinckley.

At Blaby, a rubber modified warm mix asphalt supplied by Tarmac was used to resurface and strengthen parts of the road. The mixture incorporates 5,000 recycled tyres, preventing them going to landfill, and the use of warm mix, instead of traditional hot mix, contributed to the reduction in carbon emissions as it required less energy to produce.

White lines on the northbound carriageway were also marked out using a cold plastic product which is said to last three times longer than traditional ones. The southbound carriageway was marked with traditional hot thermoplastic road markings to allow a direct comparison of the durability
and performance of both products over the coming years. In addition, all the bituminous material removed from the carriageway during resurfacing works has been identified for reuse with the new asphalt base layer containing 25% reclaimed asphalt and the surface layer containing 10%.

The three projects – funded through a successful £5 million bid awarded through the Department for Transport’s Challenge Fund to assist with recovery following Covid-19 – will have generated over 21,000 tonnes of worn-out carriageway material for reuse while the new materials used on the schemes incorporate approximately 3,700 tonnes of reclaimed asphalt.

Cllr Ozzy O’Shea, Cabinet Member for Highways and Transport, said: “Using recycled and carbon friendly components for our road improvements emphasises our commitment to improving the environment and is in line with the council’s net zero carbon pledges.”

Brian Kent, National Technical Director at Tarmac, added: “It’s fantastic to see Leicestershire County Council embracing the many benefits of these new asphalt technologies. It is the first authority to use the new rubber modified warm mix material for a project of this scale and it is vital that others follow their lead in adopting the use of the more sustainable highways solutions available if net zero targets are to be reached.”

Across the bypass projects, the council is saving a total of 32 tonnes of carbon, estimated to be the equivalent of the emissions generated by travelling over 165,000 miles in a standard car.

Largest ever use of reclaimed asphalt on M3

A section of the M3 in Hampshire has been resurfaced using warm mix asphalt containing the highest proportion of reclaimed asphalt (RA) ever on the strategic road network.

The asphalt includes 70% RA content in the base course and 50% in the surface course, reducing the use of primary materials (aggregates and bitumen) by 55%. Some 1,800 tonnes of planings were taken from a previous project on the M3 and were stored and processed before reuse.

Using warm mix asphalt reduced the production temperature from 180⁰C to 130⁰C, resulting in further carbon emission savings from a reduction in the energy used.

Matthew Wayman, Senior Pavements Advisor at National Highways, said: “We were happy to support this exciting opportunity presented by our supply chain colleagues at FM Conway and Kier Highways, and early collaboration gave us confidence that the materials installed would deliver the same level of performance as conventional materials.

“Although it has been common practice for many years to use a degree of recycled asphalt, this is a major step forward. It will help us reduce the amount of new materials needed which in turn significantly reduces our carbon footprint by cutting the emissions and energy required to excavate, manufacture and transport the materials needed to make the asphalt.”

The section of the motorway – on the northbound carriageway between junctions 6 (Black Dam Interchange) and 5 (near Hook) – will be monitored regularly to assess performance. National Highways (formerly Highways England) will look towards routinely using more recycled content in its resurfacing work, saving carbon and helping it meet its net zero ambitions.

Cumbria trials to cut carbon footprint

Cumbria County Council has been selected to carry out tests using new highways technology and methods on its local roads which could revolutionise the highways and waste industry.

Through its involvement with the ADEPT (Association of Directors of Environment, Economy, Planning & Transport) SMART Places Live Labs programme, a £22.9 million initiative funded by the Department for Transport (DfT), the council is investigating the sustainability and suitability of using additives derived from waste plastics within its highways surfacing programme. Its aim to reduce the carbon footprint of its highways schemes and provide a more resilient road network.

The council has been working on the Live labs project with Hanson, which is trialling Shell Bitumen LT R (low temperature recycled) which uses a chemically recovered waste plastic to make it compatible with bitumen, without compromising performance or re-use at the end of its life.

Designed to work at production and laying temperatures up to 30OC lower than conventional asphalt, Bitumen LT R helps to lower carbon emissions through reduced energy use during asphalt production, with every kilometre of road laid using it estimated to prevent 450kg of plastic waste going to landfill – saving one tonne of CO2 emissions. Shell’s Cariphalte AgeSafe bitumen, which incorporates an additive to prolong the life of asphalt surfacing, is also being trialled.

The trials are taking place over three different sites in Cumbria – two in Penrith and one at Nenthead in the North Pennines – as well as at Hanson’s office in Penrith where future coring and testing can be undertaken at regular intervals over the coming years to track the ageing behaviour of the asphalts. The diverse trial settings will provide comprehensive performance results. The three asphalts were produced at Hanson’s Shap asphalt plant in Penrith.

In total 450 tonnes with Bitumen LT R and 340 tonnes with Cariphalte AgeSafe product were laid along with 300 tonnes of standard product as a control.

Cllr Keith Little, Cumbria County Council Cabinet member for Highways and Transport, said: “Cumbria County Council is pioneering the use of waste plastic material in our highways, and we’re delighted to be the first in Europe to trial Shell Bitumen LT R product through the ADEPT Live Labs programme. I look forward to seeing the results of this trial taking place here in Cumbria on the A689 at Nenthead.”

Long-life binders trial set to help decarbonisation goals

A new bitumen binder, which aims to extend the lifespan of roads and reduce the need for maintenance, is being trialled by Highways England in Northamptonshire.

Motorways and major A-roads in England are typically expected to be resurfaced every 10-12 years because the effects of high volumes of heavy traffic, water ingress, UV exposure and oxidation cause the surface to deteriorate and crack.

Laboratory tests, however, have shown that TOTAL STYRELF® Long Life can protect the road surface such that roads built with it could last for longer, without the need for intervention.

The product is designed to be more resistant to the elements by oxidising more slowly. This slows down the ageing process meaning that the road surface stays flexible for longer. Consequently, the binder’s initial performance characteristics, such as resistance to fatigue, fretting, and thermal cracking, are retained for longer.

More durable road surfaces that require fewer repairs lead to lower whole-life carbon emissions by eliminating maintenance activities and bring about efficiencies and less disruption for road users.

TOTAL UK worked in partnership with Highways England and Tarmac to resurface a busy section of dual carriageway on the A43 near Silverstone, Northamptonshire, to trial the new mixture.

Rick Ashton, Market Development Manager at TOTAL UK, said: “Our key focus is Sustainability through Durability and these long-life binders will contribute to achieving clients’ decarbonisation goals by delaying roadworks, which saves manufacturing, transport and installation energy, and associated emissions. This trial paves the way for enhanced highways asset management and predictive deterioration modelling for Highways England.”

Three sections of the A43 have been resurfaced in the trail, which could run for up to 15 years. The first has been resurfaced with a standard bitumen while two use TOTAL STYRELF® variants eXtreme 100 and Long Life.

Experts from TOTAL UK will take samples from each section of the carriageway at regular intervals to measure the ageing performance and key characteristics of the bitumen, and to understand the degradation caused by water, oxidation and UV exposure.

The new technology has previously been tested in the laboratories of TOTAL, and on sections of road in Holland and Germany, but the A43 trial is the first time it has been used with such high traffic levels.

Mike Wilson, Highways England’s Chief Highways Engineer, said: “We’re always looking for innovative ways to help us keep England’s motorways and major A-roads in good condition. The ultimate priority for us is safety, so we invest in new technology and materials to keep those using the roads safe. Longer lasting roads also means fewer roadworks, less disruption for motorists and a more sustainable network for everyone.

Collaboration on resurfacing scheme to boost carbon savings

Westminster City Council is driving down the carbon emissions associated with road maintenance as part of its target to be net zero carbon by 2030.

Working with FM Conway, it has laid a Warm Mix Asphalt (WMA) surface course containing 85% recycled material on Third Avenue in the Queens Park district.

A single layer solution, SureLayer® E, delivered the high recycled content as a combination of high Polished Stone Value (PSV), Reclaimed Asphalt Pavement (RAP) and ‘recovered aggregate’.

Mark Flint, Head of Technical at FM Conway, said: “This product is challenging conventions around the amount of RAP that can be incorporated in road surfaces and is also delivering carbon savings via the use of a more sustainable WMA technology.

“WMA is mixed and laid at a reduced temperature, which cuts energy usage and reduces the associated production carbon when compared to a traditional hot mix asphalt. As a result, the use of the combination of technologies in the overall scheme, including transport, has produced a 40% carbon saving.”

In total, the 760 tonnes of material supplied by FM Conway’s Heathrow asphalt plant were laid in a single layer by its surfacing division, which increased productivity and reduced the number of lorry movements by 55%.

“This has been a great collaborative scheme between FM Conway and Westminster City Council,” added Mark Flint.

“Together we have maximised the amount of locally sourced recycled materials, as well as reducing the number of vehicle movements through the use of single layer technology. This also decreased the time spent on site resulting in us handing back the street to Westminster and its residents in an efficient and timely manner.”

Phil Robson, City Highways Head of Operations, Westminster City Council, said: “This innovation supports the goal of achieving net zero carbon by 2030 while providing the durability we need to maintain our highways asset to the highest standards.”

Benefits of the 85% recycled material used in the Westminster scheme:

  • High recycled content contributes towards a circular economy and a more sustainable construction method for treating carriageways.
  • The use of SureLayer® E means the carriageway can be resurfaced in one pass, reducing time spent on site allowing the highway to be reopened sooner and limiting disruption to the community.
  • WMA reduces energy consumption and embodied carbon.
  • WMA can provide greater durability due to reduced ageing of the bitumen in the manufacturing process.
  • An odour suppressant was used in the manufacturing and installation of the material, helping to deliver a reduction in odours for both operational staff and the wider public.


Reducing the carbon impact of roads

The UK’s first carbon neutral road scheme included the use of a low energy production technique, recycling and carbon offsetting and has been carried out as part of a Highways England (HE) resurfacing project in Cumbria.

The road improvement project included full-depth recycling of the dual carriageway between the M6 junction 36 and Brettargh Holt roundabout, along with the roundabout at junction 36. It forms part of the A590 scheme designed with a low carbon strategy to ensure safer, smoother journeys for road users.

The heavily trafficked route had come to the end of its life with potholes and uneven surfacing posing a safety risk to road users. HE’s objective was to ensure the new road was constructed quickly, safely and with minimum disruption to customers and the local road network, while meeting its ambitious carbon reduction targets.

Early contractor involvement (ECI) 18 months prior to the contract starting, with principal contractor AE Yates and designer AMEY, saw Aggregate Industries recommend a Foamix approach.

This design option meant that the structural layers of the existing road were recycled and reused back into the new road by producing an ex situ cold recycled asphalt which, when combined with the company’s SuperLow asphalt, helped to achieve a carbon neutral scheme.

An onsite mixing plant ensured a continuous and consistent Foamix material. This was supported by a fleet of dumper trucks to transfer the mixed material to site and return the extracted planings, maximising efficiency and allowing 1,000 tonnes of Foamix asphalt to be laid per night. The team worked 24 hours a day across two shifts, ensuring minimum disruption to the local area and keeping ahead of all key deadlines.

Using this approach reduced CO2 emissions and negated the need for, and costs of, truck movements relating to initial waste disposal or recycling to a remote plant, improving the sustainability credentials of the project. The result was a 43% reduction in carbon emissions compared with using conventional resurfacing materials and methods.

In a first for the asphalt industry, Aggregate Industries purchased a number of credits to offset the remaining carbon on the scheme through its partnership with Circular Ecology (a non-profit organisation).

Construction took place safely under COVID-19 regulations with 50,000 tonnes of material extracted from the original pavement and recycled. Of this, 23,188 tonnes was used with the Foamix laid using wide pavers (extended to eight metres); 4,062 tonnes was reused within asphalt; 2,749 tonnes used on site; and the remaining 20,000 tonnes reused on the A590 Cross-a-Moor Roundabout Scheme and the strategic road network.

Guy Edwards, CEO at Aggregate Industries UK, said: “By working collaboratively through ECI, we were able to identify a low-carbon approach designed to provide significant environmental and, in turn, cost benefits.”

“As we continue to work more closely together as an industry and utilise our expanding range of eco-friendly products and services, we can start to make a real difference when helping to deliver essential infrastructure projects.”

CEMEX has also launched a new range of reduced carbon asphalts, which includes the option to offset residual CO2e to make it certified CarbonNeutral®.

VIALOW low temperature, low carbon asphalt, uses a bitumen additive to enable manufacture at up to 40°C lower than standard asphalt mixtures, without compromising performance, and with the added benefit of achieving up to 20% reduction in embodied carbon emissions.

Carl Platt, Director of Asphalt, Paving and Building Products for CEMEX Europe, said: “As technology and the industry shifts toward low carbon asphalt, the best interim way to sequester the rest of the CO2 footprint, to make it a carbon neutral product, is through carbon offsetting. This is what we are doing, working with Natural Capital Partners, with VIALOW Zero.”

In addition to its low carbon credentials, the new range offers customers other benefits associated with Warm Mix Asphalts including improved safety and efficiency, with increased shift outputs and earlier reopening to traffic, reducing disruption to road users.

“We recognise that future construction needs to be balanced with the effect it is having on the environment,” added Carl Platt.

“We are committed to improving the sustainability of our operations and supporting our customers to do the same. This new range makes it simple for customers to choose more sustainable and environmentally-friendly asphalts that have a lower embodied carbon, offset residual emissions and help drive change.”

Westminster’s ground-breaking low-carbon roadworks

Westminster City Council has completed a six-week project in King Street, which has used a series of low-carbon measures to cut project carbon emissions by almost 75%.


The project, to repair public highways and upgrade the footway, used electric vehicles, tools, welfare, and recycled equipment, to remove the traditional need for diesel and petrol engines. The charging points for electric vehicles and tools installed will remain in situ for local residents use as a legacy of this project.

Among the low-carbon measures was the use of GreenPatch, a high recycled content permanent pothole and patch repair asphalt, supplied and laid by contractor FM Conway.

Cllr Andrew Smith, Westminster’s Cabinet Member for Highways & Environment, said: “If we are to truly tackle the effects of climate change and meet our ambitious target of Westminster being carbon neutral by 2030, then we must revolutionise the way we do things as a local authority, which includes the way we carry out our essential daily works and operations.

“This scheme is not only ground-breaking but also a catalyst for change in the way we do things. We hope that the success of this trial will see public realm works across the city transform for the better and help us towards maintaining a greener and cleaner Westminster.”

Data collected throughout the trial will be used to calculate the total carbon savings, with the aim of reducing emissions, cutting noise pollution and ultimately providing a blueprint for all future works to be low-carbon, low-emission, and sustainable.

Ealing Embraces Single Layer Low Carbon Asphalt

Conducting resurfacing works on the busy streets of London is challenging at the best of times. Throw in buses on diversion, bridges, restricted access/short possessions and tar contamination and you have additional obstacles to overcome in the design and execution of a highways project – and all with reduced CO2 emissions and public health to consider.

This was the position Ealing Highways was in when it undertook the resurfacing of Mandeville Road, the A312, directly outside Northolt Underground station and a busy bus route connecting the A40 to Harrow.

The original design called for 70mm of binder course with a 40mm surface course to be laid on the bridge over the railway line during a four-night period, but a rethink was needed when site investigations showed tar contamination at 90mm depth. The challenge then became to leave the tar contamination undisturbed and avoid the significant cost of disposal of a hazardous waste. The brief also called for a dense and durable design suitable for the rigours of London life.

Ealing Highways contacted Tarmac who proposed planing to 80mm and laying UltiLayer SMA 14 from the company’s range of polymer modified bitumen asphalts in a single layer.

Accredited contractor Toppesfield was supported by Tarmac’s technical team to ensure the works were successfully completed and the necessary compaction was achieved. To ensure the thick inlay had cooled sufficiently to white line and open to traffic in time, the UltiLayer was specified as a Warm Mix Asphalt. This method of production also provided the additional benefit of reducing the project’s CO2 footprint by around 10% and reducing on-site emissions by around 80%, supporting London Borough of Ealing’s Public Health objectives.

The planing and laying operation was carried out over two nights with material supplied from Tarmac’s nearby plant at Hayes. In total 580 tonnes of UltiLayer was laid, saving 220 tonnes on the original 110mm deep design. The UltiLayer also used 14mm steel slag aggregate, transferred from Tarmac’s works at Port Talbot by rail. This aggregate carries a zero CO2 rating as it is a by-product of the steel making process.

Roger Eke, Technical Product Manager at Tarmac, said: “This is the third significant scheme on which Ealing Highways has specified UltiLayer. The dense, low texture mixture and high-grade polymer modified bitumen makes it a sensible choice for highways engineers looking to overcome the many issues associated with an ageing road network that carries high volumes of heavy traffic.”

Richard Stiles of Ealing Highways’ Infrastructure Renewal Team added: “We are expecting the new surface to cope with the demands of relentless traffic and, although we will monitor the site in future, we are confident the right choice was made as we avoided the extra cost of tar disposal and reduced the duration of works by two nights, saving money and minimising disruption. Tarmac has delivered a durable material designed for the long term which offers reduced carbon emissions and noise pollution.

“Overall, the project was delivered at no additional cost to the original budget and resulted in improved ride quality, appearance and reduced noise pollution.”

Smart surfacing used in listed bridge refurb

An iconic Grade II listed bridge will soon reopen following a comprehensive three-year refurbishment programme, including the use of a specialist asphalt.

Runcorn’s Silver Jubilee Bridge, which spans the River Mersey, was closed for repairs following the opening of the Mersey Gateway in October 2017, the first time it had undergone major refurbishment since it opened in 1961.

The revamp, led by Halton Borough Council, came with a challenging brief – requiring an asphalt solution that could help reduce water ingression, improve durability and be laid at a minimum depth of 70mm over a waterproofing membrane. In addition, as vibration on the bridge deck is not permitted, it was essential that the asphalt did not require a high degree of compaction.

Cllr Stan Hill, Portfolio Holder for Highways and Transport for Halton Borough Council, said: “The design of any bridge deck surfacing can be challenging, but even more so when you only have 70mm of coverage on a Grade II listed bridge. We wanted a solution that was flexible enough to withstand movement, could help reduce water ingression through the asphalt onto the bridge deck, improve durability and still give good deformation resistance – all at this minimum inlay thickness.”

Following early involvement in the project, Aggregate Industries’ Contracting Division constructed a 40mm lower layer of very dense and highly rut resistant Hot Rolled Asphalt, which was then overlaid with 30mm of ProLay Ultra cl.942 asphalt.

The material was laid using state-of-the-art smart surfacing technology to capture the data required to support asset management, giving Halton Borough Council as-built digital data records straight from the paver.

Paddy Murphy, Managing Director of Contracting at Aggregate Industries, added: “Given the complexity of this bridge renovation, we created  a bespoke ProLay Ultra asphalt mix manufactured, supplied and laid by our expert team It’s a great example of how this customised approach was able to meet the difficult brief of creating an asphalt solution that didn’t require a high degree of compaction yet still had low voids.”