Highways England is accelerating the use of warm mix asphalts as a standard throughout its supply chain. This is part of a drive towards net zero carbon emissions.
The UK Government owned company has been using the material since 2015 and a collaborative programme with the supply chain and extensive research now means that is can be freely used throughout the Strategic Road Network (SRN).
Previously, an application was needed for a departure from standard. Highways England is now asking all those involved in the construction and/or maintenance of the SRN, in particular designers and main contractors, to use warm mix asphalts (WMA) as it is another step toward net zero.
WMA technology can offer enhanced efficiencies as well as lower production carbon, with CO2 savings of up to 15% when compared to conventional hot mix asphalt. While typical asphalts are produced at up to 190°C, the simple principle behind WMA technologies is to manufacture asphalt at reduced temperatures but with additional additives, thereby using less energy and delivering meaningful carbon savings, without compromising performance.
WMAs are 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 CO2 a year, the equivalent of cutting around 300 million miles of car journeys.
This could also help save up to £70 million per year through an increased in shift outputs. WMAs can also be recycled back into new asphalts, meaning waste is prevented. WMAs can also be laid using existing equipment and bring other benefits, including:
The lower production temperatures of WMAs reduce the carbon emissions associated with asphalt production by up to 15% compared to Hot Mix Asphalts. More widespread use of WMAs will help Highways England to achieve its aim of net zero by 2050.
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 enabling more material to be laid within a working window, reducing the overall timeframe 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.
Due to being laid at lower temperatures and the increased amount that can be laid in a single shift, it also means less construction joints in the road requiring less maintenance in the future. This again increases the long-term benefits of the technology, life-time cost and need to undertake further maintenance.
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 is something which lies at the heart of Highways England’s net zero carbon plan and the Department for Transport’s decarbonisation plan with both organisations aiming to shift he 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 USA and over 15% in France – but WMAs remain under-used in the UK, where they currently represent less than 4% of overall asphalt production. At Highways England, WMAs previously required an application from the supply chain for a departure from standard.
Highways England’s net zero carbon plan aims to rapidly cut carbon from road construction, maintenance and operations as well as supporting the transition to zero emission vehicles.
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