Construct - Issue 51

Innovation

FROM TRIAL TO TRIUMPH

FM CONWAY AND TRANSPORT FOR LONDON ARE CELEBRATING THE OUTCOME OF A LANDMARK TRIAL TO PROVE THE EFFECTIVENESS OF RECYCLED ASPHALT PRODUCT (RAP)

The A1 Mill Hill trial proved that RAP could match traditional mixes in durability and sustainability, marking a major step towards lower carbon road construction. FM Conway believed in the benefits of the circular economy, extending the lifecycle of materials as far as possible, long before it was fashionable. Recycling asphalt and aggregates for highways construction and maintenance work minimises waste, cuts pressure on virgin resources and lowers carbon emissions. However, historically, there were doubts about whether high recycled asphalt could meet the requirements of the strategic network. Now the business has the data to prove that it can. Back in 2016, when the trial began, it was commonplace to incorporate 50% recycled content into the base and binder course of strategic routes, but its use in surface courses was restricted to just 10%. The thinking was that high recycled content mixes couldn’t provide adequate skid resistance or durability.

FM Conway had been investing in research to expand the use of RAP and needed a like minded client who could help to challenge these misconceptions by taking material mixes out of the lab and onto the road. Transport for London (TfL) fit the bill. Having worked closely for many years, FM Conway and TfL had built a strong foundation of mutual trust and confidence in delivery. The pair launched an ambitious trial to test higher percentages of recycled asphalt on the A1 at Mill Hill, a high-speed, strategic route to the north of London. FM Conway resurfaced three lanes, two with 50% RAP in the surface course and one with a traditional mix as a control. Between 2016 and 2025, the material was closely monitored. TfL commissioned an independent supplier to extract 18 core samples from the three lanes to assess performance. The verdict was clear – the tests proved conclusively that high RAP works.

LOCATION

Potters Bar

M25

M25

Elstree

M1

MILL HILL

Edgeware

Finchley

M1

Harrow

Brent Cross

Wembley

Camden

The results show that sustainable road construction is far from a

compromise; it’s the future.

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