Nynas news

27/08/2018 14:04

Effective solution for reduced maintenance

All municipalities have at least one section of road that constantly requires maintenance, surfaces that can never be satisfactorily repaired and are always on the waiting list for new measures. One such example is the junction of Pilsworth Road and Moss Hall Road in the English town of Rochdale.

On one side of this signalised T-junction is the access to a 200-acre distribution park, while on the other is a quarry. The junction is situated in a strategic motorway location, with major interchanges with both the M62 and M66 less than 1 km away. As a result, it is very heavily trafficked, particularly by heavy goods vehicles (HGVs).

The traffic calculation for the junction’s 20 years design period was estimated at 50 million standard axles (msa), making it one of the busiest single carriageway roads in Europe in terms of the volume of commercial traffic.

The site was resurfaced in traditional hot rolled asphalt (HRA) over ten years ago, but deteriorated rapidly and within two years it was already subject to regular maintenance issues. These included repeated early life failures of the traditional materials, fretting and rutting of the surface, and failure of the binder course layers.

In 2016, after nearly a decade of remediation at the junction, Rochdale Borough Council decided to look for a more sustainable, long term solution that would ensure the junction could withstand the heavy trafficking without the need for constant ongoing maintenance.

That solution involved planing off the existing pavement, and replacing it with a geotextile layer and then new binder and surface course layers incorporating Hanson’s Tufflex HD+ heavy duty asphalt mix.

“The design required a solution for slow moving HGVs negotiating the junction,” explains Rochdale Borough Council assistant engineer Paul McCaffrey.

“After speaking to Hanson, Tufflex HD+ was recommended to us. The technical data indicated that the surfacing would achieve a stiffness of 7000 MPa.”

Hanson technical services manager for aggregates and asphalt, Jon Sharp, adds:
“We offered Tufflex HD+ 20 mm for the binder course layer and Tufflex HD+ 14 mm for the surface course as the most robust asphalt mixes Hanson have, giving the best surface finish for this particular scheme.”

Tufflex HD+ contains Nynas Endura Z2, a premium polymer-modified hot-mix binder for heavy duty applications. Nynas Endura Z2 significantly enhances the toughness, rutting resistance and flexibility of a well-designed asphalt mix providing good protection against damage caused by heavy, slow moving traffic.

“While it is hot, the Nynas Endura Z2 helps to lubricate the mix to enable optimum compaction in line with the unique design,” explains Sharp. “When cold and in service, its helps to protect the lower layers from water ingress, add stiffness as well as flexibility, and to actively resist the tearing affect that HGV’s tyres have while slowly turning across the junction at the traffic lights.”

The carriageway reconstruction was carried out over a period of two weeks during August 2016, by Balfour Beatty Living Places using local civil engineering contractor J Cooney who used Manchester Road Surfacing. A total of 1 000 tonnes of Tufflex HD+ was supplied from Hanson’s asphalt plant in Leeds, and laid using a Vögele paver. Compaction came from a combination of a 12 tonnes deadweight roller and a 4.5 tonnes vibrating roller.

“This stretch of road is servicing one of the busiest industrial estates in Europe, so inevitably the road has failed in the past,” says Sharp. “The hope is that our product, combined with the geotextile, will give the surface a much longer lifespan.”

The proof will be in the long-term performance, but so far, the material is holding up well, says McCaffrey:

“Eighteen months after surfacing the site has presented no maintenance issues as regards to the surface condition.”

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