A road surface mix containing significantly more recycled aggregate than usual is being trialled on the A1 in north-west London.
Infrastructure services company FM Conway, which has asphalt plants at Heathrow (pictured) and Erith and is leading on the scheme, started laying material on three lanes of the major road on 22 March.
The trial, in partnership with Transport for London (TfL), will discover if the mix provides adequate skid resistance and durability compared to typical material that contains less than 10% recycled aggregate.
At present, it is not unusual to incorporate 50% recycled content into the road base and binder layers but surface mixes are traditionally limited to the 10% proportion.
Because durability is one of the factors to be tested, it could be a number of years before a full assessment is possible.
Tim Metcalf, aggregate and asphalt director at FM Conway, said: “We’re confident that the trial will answer any doubts about the use of high recycled content asphalt for both surface courses and the base and binder courses of strategic roads.
“High recycled content asphalt not only meets specified safety requirements, but can support the highways industry in its drive to be more resource efficient.”
Dana Skelley, TfL’s director of asset management, said: “This unique trial will help us test how durable recycled asphalt is with a view to efficiently implementing this process across the highway network in the near future.”
The recycled content mix is compliant with clause 942 of the Specification for Highway Works and incorporates FM Conway’s selected binder and aggregates, as well as Arizona Chemical’s Sylvaroad binder performance additive.
Metcalf said the firm recycles 98% of highways arisings from the road maintenance projects it works on after investing heavily in its recycling infrastructure during recent years.