Transport for London (TfL) ) has become one of the first highway authorities in the UK to demonstrate the long-term performance and durability of a recycled running surface.
TfL contractor FM Conway (now part of Vinci) used a trial mix of 50% reclaimed asphalt pavement (RAP) on a section of the A1 at Mill Hill in north London back in 2016. Nine years on, the results are in 鈥� it has passed all tests.
The trial has confirmed that the material can endure frequent, heavy traffic and matches the performance of traditional asphalt, in terms of quality, texture, safety, and maintenance.
Alongside intensive monitoring, laboratory testing on the material鈥檚 structural behaviour and response to force and load showed that it maintained its firmness and integrity over the trial period. Industry standards of the time restricted the use of RAP in the top layer of roads to just 10% because of a long-standing industry perception that recycled content was suitable only for the lower layers of roads.
Increasing the use of recycled materials in roads reduces both construction waste and the need for importing new raw materials, thus helping to reduce carbon emissions.
Building on the success of this pilot, TfL has carried out further trials on A40 Westway and now promotes high RAP asphalt as an option in future highways works on its network.
As an early adopter, TfL is well positioned to share findings, guidance and outcomes to support wider industry learning and innovation to encourage broader implementation of 50% RAP mixture proportion, it says.
Isabel Coman, TfL鈥檚 director of engineering and asset strategy, said: 鈥淲e are committed to reducing carbon emissions across our assets and infrastructure to help us meet our net zero targets. By trialling a higher proportion of recycled asphalt on the A1 at Mill Hill, we鈥檝e become one of the first authorities in the UK to successfully incorporate 50% RAP in the top layer of one of our major roads and proved its ability to withstand heavy traffic loading. This trial demonstrates our commitment to sustainability and gives a strong signal to the supply chain that we are seeking innovative solutions to reduce the embedded carbon in our major construction materials. We hope this encourages other highway authorities to conduct similar trials and continue to drive improvements in the sustainability, reliability and durability across the sector.鈥�
FM Conway technical director Mark Flint said: 鈥淭he use of high levels of recycled asphalt has grown significantly but there鈥檚 still a long way to go to making it standard practice. The results of our work with TfL validate what we鈥檝e known all along: that RAP can deliver comparable results to mixes made entirely with virgin materials. The trial has proven that sustainability and innovation advances can be made without compromising the quality and durability of our roads. Partnerships built on trust, like the one we have forged with TfL, are key to continuing this progress.鈥�
TfL now incorporates recycled asphalt where feasible and works with suppliers at project level to identify and implement opportunities for increasing RAP usage wherever applicable. Alongside this, TfL is developing and implementing decarbonisation plans for concrete and steel, the two highest carbon-emitting materials in construction.
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