Highways England opts for warm mix asphalt

The company in charge of maintaining England’s strategic highways, including motorways and main roads, is officially shifting its preference towards using warm mix asphalt. Highways England lays out the case for its decision.*
Asphalt Paving, Compaction & Testing / August 26, 2021 2 minutes Read
By David Arminas
Hot to trot for warm mix: less risk to workers of burns, fumes and poor visibility when wearing safety eyewear (image courtesy Highways England)

Highways England has announced that it is accelerating the use of warm mix asphalt as standard across its supply chain for the Strategic Road Network.

The UK government-owned company said the move is part of a drive toward net-zero carbon emissions and follows a collaborative programme with its supply chain partners.

Highways England has allowed use of the material since 2015 but only after a contractor attains an application from the company for a departure from standard asphalts. Highways England is now asking all companies, including designers and main contractors involved in the construction and maintenance of the Strategic Road Network – England’s motorways and A-class main trunk roads - to use warm mix asphalt (WMA).

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

While typical asphalts are produced at up to 190°C, the simple principle behind WMA technologies is to manufacture asphalt at reduced temperatures but using additional additives. This consumes less energy and delivers meaningful carbon savings, without compromising performance.

Warm mix is produced at temperatures of 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 CO2 a year, the equivalent of cutting around 480 million kilometres (300 million miles) of car journeys.

It would also help save up to US$96 million (£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 brings other benefits. Lower production temperatures of WMAs reduce the carbon emissions associated with asphalt production by up to 15% compared to hot mix asphalts. A widespread use of WMAs will help Highways England to achieve its aim of net-zero carbon emissions by 2050.

Reduced laying temperatures mean that WMAs take a shorter time to cool. This means that greater volumes of asphalt can be laid in one shift. Also, the finished surface can be opened to traffic earlier than when using hot mix, all without the risk of the material deforming under heavy loads. This will increase a contractor’s productivity by enabling more material to be laid within a working window, reducing the overall time-frame of the work and delays to motorists.

There is a health and safety aspect when producing and using WMA; it produces around 50 per cent fewer fumes for each 10°C reduction in temperature. There is less risk to workers of burns, exposure to fumes and the impact of steam on visibility, particularly when wearing safety eyewear.

Improved durability

Because an increased amount of WMA can be laid in a single shift, there are fewer construction joints in the road surface which means less maintenance in the future. This saves money but also extends the life-span of the asset and means fewer road works for maintenance that can cause traffic congestion for road users.

“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,” said Malcolm Dare, executive director of commercial and procurement at Highways England.

“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 decarbonisation plan, with both aiming to shift the UK to a low-carbon economy,” said Dare.

WMAs account for significant volumes worldwide, according to the UK government’s All Party Parliamentary Group on Highways’ report that was published in September 2019. It is almost 40 per cent of asphalt production in the US and over 15 per cent in France. However, WMA remains under-used in the UK where it represent less than 4 per cent of overall asphalt production.

Having already received more than 250 applications from contractors to use WMA on the Strategic Road Network at over 300 locations, including the M1, M4, M5, M6, A36, and A303, the change in policy makes that process easier for the supply chain.

Rick Green, chairman of the UK’s Asphalt Industry Alliance, said his organisation and its members welcome the announcement by Highways England. “The AIA has long-advocated the role that WMA can play in reducing production carbon emissions, improving efficiencies and delivering health and safety benefits.

Green said he is looking forward to the removal of practical and procurement barriers that until now has prevented its broader adoption. “This will reduce time and costs associated with seeking departures and will also help pave the way for the wider acceptance of WMA on local roads which represent 97 per cent of the total network, delivering scalable carbon reduction benefits.”

“We are delighted that we’ve formed a group from across the supply chain which is focused on embedding carbon reduction measures across Highways England’s schemes,” said Paul Gott, project sponsor from Morgan Sindall Infrastructure, a major contractor for Highways England. “Warm mix asphalt is the first carbon efficiency project on the group’s extensive carbon reduction plan, which is evolving and already identifies several short, medium and longer-term goals.”

Tim Jordan, project delivery lead with contractor Balfour Beatty, said Highways England’s announcement will “drive meaningful, sustainable change in the supply chain” as the supply chain works collectively towards a net-zero future. “Having joined the United Nations’ Race To Zero campaign, further bolstering [Balfour Beatty’s] sustainability strategy called “Building New Futures”, our commitment to using sustainable materials across our portfolio is yet another example of how we are driving a sustainable, greener, lower carbon future for all.”

Malcolm Simms, director of the UK’s Mineral Products Association, said his organisation and its members have been working closely with Highways England for a number of years to provide evidence of the benefits of warm mix asphalt in order to give specifiers the confidence to make a shift to these solutions. “This is a significant first step on ou collective and challenging net zero journey,” he said. “It’s great to see lower carbon asphalts being enabled as a matter of routine, rather than by exception.”

Highways England said that its 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 puts roads at the heart of Britain’s net-zero future through three key commitments; achieving net-zero for its 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.

The full net-zero plan is available on the Highways England website.

*Much of the information contained in this article is an edited announcement from Highways England this month.