The future of a sustainable highway is now

Products that can help to significantly reduce the carbon footprint of laying a road surface are available now, but too many highway authorities are still hesitant to try new technologies, says Tarmac’s national technical director, Brian Kent

Warm mix asphalts which are manufactured and laid at around 40 degrees less than traditional hot material have been performing well for many years, but still only represent around 5% of market share in the UK.

Two years ago, the All Party Parliamentary Group on Highways concluded that the use of warm mix asphalt can reduce CO2 emissions associated with asphalt production by as much as 15%.

The case for warm mix was strengthened in 2019 after the introduction of guidance for warm mix into the specification for highway works, which many local authorities follow.

But still, the quantities of lower temperature asphalts specified remain low.

It now needs senior industry and political support to champion materials such as warm mix asphalt if the UK’s transportation sector is to meet its 2050 carbon reduction target.

If warm mix became the default for asphalt specified across the country, then overnight, we could see around 70 or 80% of asphalt installed in this country being mixed and laid warm.

There is also a need for more collaboration between local authorities to allow a product deemed suitable in one area to be readily accepted in another. At the moment, some local authorities are happy to specify new materials, whereas others will only agree if they carry out trials and monitor its performance over five years or more.

Another highway development that is not being exploited as much as it could is for binder and surface courses to be replaced as one homogeneous material, rather than in separate passes. By laying single-layer materials, you make a considerable sustainability saving by reducing time on site and the associated operations.

A more recent introduction to our sustainable products portfolio is rubber modified asphalt, which incorporates recycled worn vehicle tyres into the carriageway.

The sector’s apparent reluctance to embrace innovative thinking is at odds with that of the public. Technology has always quickly been embraced by consumers, over a wide range of industries, including mobile phones and cars. But when it comes to our industry people can be reluctant to take on what they perceive as a risk. Historical or procurement barriers restrict innovation uptake in terms of what has been specified, with a lack of flexibility to change and embrace innovation.

While environmental awareness is growing in the sector, cost still appears to be the main driving factor behind product specification. However, just because a product is greener and can be slightly more expensive per tonne it does not mean that the whole life cost is more expensive – by reducing site operations and extending pavement life, costs can be reduced.

Brian Kent is National Technical Director at Tarmac. Tarmac is sponsoring the Civils and Materials Theatre at Highways UK at the NEC on 3/4 November 2021

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