Resurfacing work sets industry standards for recycling

Resurfacing work on the M25 between junctions 6 and 7 has set an industry standard for recycled roads in the UK.

A joint partnership between Mouchel and Tarmac on behalf of the Highways Agency has seen more than 700t of existing porous surface course recycled into the new road surface using 40% recycled asphalt pavement material - a first on a motorway or major A road maintained by the Highways Agency.

The scheme is part of the Highway Agency's ongoing programme of investment in maintaining more than 4,000 miles of motorway and major A roads in England.

The success comes on the back of a scheme completed in 2007 on the clockwise carriageway at junction 7, in which up to 25% of the aggregate from the existing surface was recycled back into the new surface course covering an area of 30,000m².

Steve Smith, project manager for Mouchel, says the firm has to be adaptable and innovative in its approach to maintaining the UK's road network for the Highways Agency.

So Mouchel presented the idea to Tarmac, which undertook laboratory testing to ensure that the new surface could meet standards for Polished Stone Values (PSV), texture, depth, skid-resistance, deformation resistance and durability. With an approved departure from standard, required for the 20mm sized thin surface course, this is also another first for the M25.

Smith says: "By re-using materials we achieve several objectives. We lessen the impact on the environment by reducing waste and carbon emissions, while at the same time reducing costs."

Night shift

Tarmac planed and removed the existing surface over three consecutive nights from around 17,000m² of the anti-clockwise carriageway at junction 7, near Reigate Hill.

The material was then transported for reprocessing at the company's Hayes asphalt plant, which has been upgraded to deliver high percentage RAP material. The new surface course was re-laid the following night as a new 20mm aggregate surfacing covering 6,900m² of carriageway.

RAP material is typically recycled in base and binder course materials and it is uncommon to re-use this material in a thin surface course, which requires high PSVs to ensure good skid resistance.

Tim Smith, Tarmac technical manager London & South East, explains: "Recycled roads offer a vital opportunity both to conserve virgin aggregates and help to re-use road planings. This work sets a high benchmark for future road schemes on the national network and, as an industry, we have an obligation to continue to develop innovative technology which can deliver a sustainable approach to road renewal."