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Highways England accelerates switch to WMA

Warm-mix asphalt

Lower-carbon warm-mix asphalts can now be used freely across the strategic road network

HIGHWAYS England is accelerating the use of warm-mix asphalt as standard across its supply chain as part of a drive toward net-zero carbon emissions.

The Government-owned company has been using the material since 2015 and a collaborative programme with the supply chain and extensive research now means it can be used freely across the strategic road network.


Previously requiring an application for a departure from standard, Highways England is now asking all those involved in the construction and/or maintenance of the strategic road network, particularly designers and main contractors, to use warm-mix asphalts (WMAs) as it moves towards net zero.

WMA technologies can offer enhanced efficiencies and lower production carbon, with CO2 savings of up to 15% compared with conventional hot-mix asphalts.

Whilst typical asphalts are produced at up to 190°C, WMA is manufactured at reduced temperatures but with additional additives, thereby using less energy and delivering meaningful carbon savings, without compromising performance.

Produced at temperatures up to 40°C lower than traditional asphalt, if all production in the UK switched to WMAs, it would save around 61,000 tonnes of CO2e a year, the equivalent of cutting around 300 million miles of car journeys.

In addition, it would help save up to £70 million a year through an increased in shift outputs, and can be recycled back into new asphalts, preventing waste. WMAs can be laid using existing equipment and bring other benefits, including:

Carbon reduction – The lower production temperatures of WMAs reduce the carbon emissions associated with asphalt production by up to 15% compared with hot-mix asphalts. More widespread use of WMAs will help Highways England to achieve its aim of net zero by 2050.

Increased productivity – Reduced laying temperatures mean that WMAs take a shorter time to cool so greater volumes of asphalt can be laid in one shift, or the finished surface opened earlier to traffic without the risk of the material deforming under heavy loads. This will increase productivity by allowing more material to be laid within a working window, reducing the overall time frame of the works and potential delays to motorists.

Improved health and safety – Reduced temperatures also help to reduce the health and safety risks associated with both production and laying of asphalt at high temperatures, such as burns, exposure to fumes and the impact of steam on visibility, particularly when wearing safety eyewear. With WMAs, fume generation is reduced by around 50% for each 10°C reduction in temperature.

Improved durability – As a result of being laid at lower temperatures and the increased amount that can be laid in a single shift, it also means fewer construction joints in the road and, therefore, less maintenance in the future.

Malcolm Dare, executive director of commercial and procurement at Highways England, said: ‘This is a big step forward for Highways England that allows us to not only achieve huge efficiency savings, but also reduce carbon as we strive for net zero.

‘Carbon reduction, along with ensuring our roads provide smooth, safe, and efficient journeys for motorists, are key and something we are constantly striving to improve for generations to come.

‘That’s why we are altering our way of working to encourage and enable the use of warm-mix asphalts as standard across the supply chain, which has efficiency, sustainability, and health and safety benefits, whilst not compromising performance.’

Carbon reduction lies at the heart of Highways England’s net-zero carbon plan and the Department for Transport’s decarbonization plan, with both aiming to shift the UK to a low-carbon economy.

According to an All Party Parliamentary Group on Highways’ report in September 2019, WMAs account for significant volumes worldwide – almost 40% of asphalt production in the US and more than 15% in France – but WMAs remain under-used in the UK, where they currently represent less than 4% of overall asphalt production.

Having already received more than 250 applications to use WMAs at more than 300 locations on the strategic road network, including the M1, M4, M5, M6, A36, and A303, among others, the change in policy will now make that process easier for the supply chain.

Mineral Products Association (MPA) director Malcom Simms said: ‘We and members have been working closely with Highways England for a number of years to provide the evidence of the benefits of warm-mix asphalts, in order to give specifiers the confidence to make a shift to these solutions.

‘This is a significant first step on our collective and challenging net-zero journey, and it’s great to see lower-carbon asphalts being enabled as a matter of routine, rather than by exception.’

Rick Green, chair of the Asphalt Industry Alliance (AIA), added: ‘We welcome Highways England’s announcement that the use, as standard, of warm-mix asphalts is now encouraged on the strategic road network.

‘The AIA has long-advocated the role that WMAs can play in reducing production carbon emissions, improving efficiencies and delivering health and safety benefits. This includes our support in 2019 of the All Party Parliamentary Group’s (APPG) for Highways (now renamed the APPG for Better Roads) ‘Working for Better Roads’ report, which encouraged the uptake of WMA solutions – including by the removal of practical and procurement barriers that prevented its broader adoption.

‘This move by Highways England will reduce time and costs associated with seeking departures and will also help pave the way for the wider acceptance of WMAs on local roads, which represent 97% of the total network – delivering scalable carbon-reduction benefits.’

Highways England’s net-zero carbon plan will see it rapidly cut carbon from road construction, maintenance and operations, and support the transition to zero-emission vehicles.

The plan will put roads at the heart of Britain’s net-zero future through three key commitments: achieving net zero for Highways England’s own operations by 2030; delivering net-zero road maintenance and construction by 2040; and supporting net-zero carbon travel on England’s roads by 2050. 


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