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Feature: On the road

After the wear and tear caused by 80 million vehicles during the past 20 years, one of Somerset’s busiest roads has been recycled. Major reconstruction work started before Christmas on the A38 at Rooksbridge, a primary route from Bridgewater to Bristol, which has been showing signs of structural deterioration for some time.

In line with the county council’s recycling policy, Geoff Dight, highways project manager for Somerset Council, says most of the £300,000 facelift has involved using material removed from the existing road, which was last surfaced in the early 1980s. “The material was planed off and moved to a nearby site where it was mixed with foamed bitumen to provide new material for relaying,” says Dight.

The product, Foamix, is a recycled asphalt product made by Foster Yeoman, with the surfacing carried out by Mendip Contracting under the supervision of Somerset’s highways partner WS Atkins. It is estimated that the use of this recycling process has saved around 1,900 tonnes of virgin aggregate and cut quarry lorry movements by about 5,700 miles. The work was funded by Somerset County Council under its Local Transport Plan.

Foster Yeoman technical manager Martin Dudley says: “Recycling can be cheaper than conventional methods and it also reduces energy consumption and CO2 emissions. It enables the use of other materials that may otherwise have to be disposed of, and increases the sustainability of highway operations.”

The initial work on the A38 at Rooksbridge involved planing off 120mm of the existing surface. This comprised an old asphalt wearing course and a base course, which had been laid over some very old surface dressing. “It was a patchwork quilt,” Dight says. “Joint and crack overbanding has been used to try to hold it together, but it was still showing up negative on our Deflectograph surveys and, visually, it was probably one of our worst roads in the county.”

The process is said to be highly efficient and relatively straightforward. Planings are taken to the Foamix plant, recycled and taken back to site in a continuous cycle. “Planings are taken from the road, screened to –20mm, which gives us a continuous grading,” Dudley explains. “We then add two powders, cement and PFA, which gives the mix strength over a period of time. Finally a foam binder is added which gives initial strength so that it can be trafficked without undue delay.”

The cement and PFA are added to the recycled planings via two feed hoppers. Water is added so that the material can be compacted properly. The material is fed into a mixer box where foamed bitumen (approx. 3.5% of the overall mix) is added before the finished product is discharged to the floor or loaded directly into lorries.

“The performance of the material is monitored by the council’s inspectors and random core samples are taken,” adds Dight. “If this trial is successful, we may look at banding groups of jobs together next year so it would be worth moving the plant in and doing 10 or 12 jobs in one go.”

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