Low-carbon asphalt on its way

Highways England is promoting a switch to warm mix asphalts (WMAs) which bring CO2 savings of up to 15 per cent compared to more traditional hot mix asphalts that are normally used. This could save around 61,000 tonnes of CO2 per year, the equivalent to cutting 300 million miles of car journeys. While typical asphalts are produced at up to 190 degrees Celsius, WMA can be mixed at temperatures around 40 degrees lower when additional additives are used, using significantly less energy. Highways England has been using the asphalt since 2015 and is now asking contractors across the Strategic Road Network (SRN) to switch to WMAs.

According to Highways England, the asphalt also has other benefits, including increased productivity. Reduced temperatures mean the cooling time is shorter, so more can be laid in a shift, while traffic can be allowed onto the asphalt more quickly. This can also reduce the length of time that roadworks are in place, reducing delays for motorists.

Lower temperatures also improve health and safety, reducing the risks of burns, fumes, and steam reducing visibility. Fume generation is reduced by half for each 10 degree Celsius reduction in temperature. Durability can also benefit, thanks to the larger amounts it’s possible to lay, with fewer construction joints in the road that will require future maintenance.

The use of WMAs previously required an application for a ‘departure from standard’, but the change in policy by Highways England will now make the process easier for the supply chain. Malcolm Dare, Executive Director of Commercial and Procurement, said: “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.”