Proving that thins can be tough

Great care is needed when applying thin surfacings – like at this site in central London – but the technique is durable, says Jean LeFebvre

Jean LeFebvre’s UL-M thin surfacing continues to prove its worth in the UK in spite of a poor perception of asphalt overlays laid to a diminished depth.

Thin surfacings have suffered recently from a bad press in the UK due to a perception that they fail prematurely. However one manufacturer Jean LeFebvre (UK) – part of the Eurovia Group – has laid its UL-M product for over 20 years in the UK and around the world and says it can dispel this perception.

The company’s Divisional Manager Jonathan Core says: “The key to ensuring the durability of a thin surfacing lies with the material constituents, designs and high quality installation practices. When the specification and design are correct and the materials are installed correctly, thin surfacings are durable and represent a cost effective solution for today’s highway engineers.”

Jean LeFebvre (UK)’s licensees have produced and laid over 20Mm² of its UL-M thin surfacing system across a wide range of UK roads since the material’s first application on the A34 in Staffordshire in 1992. Performance on this site and at many others – including the M25 and the A1(M) Gateshead Bypass – have exceeded initial expectations, the company says.

UL-M is not just a UK success story. Over 100Mm² has been installed worldwide and not just on roads. Following discussions with Airports Company South Africa in 2008 the product was installed on two runways of the country’s third largest international airport in Bloemfontein.

Laboratory analysis of thin surfacing constituents

After four years service the 22mm thick surfacing is showing no visual defects along with excellent friction values. This success has resulted in a further five runways being resurfaced with the product in the country, along with the runway at Hosea Kutako International Airport in Windhoek, Namibia.

Developed in France in the 1980’s UL-M thin surfacing can be laid as thin as 15mm. The system uses high performance polymer modified bitumens which have high cohesion, low thermal sensitivity and excellent resistance to ageing. Modification of the company’s Evatech product range makes it possible to adapt the choice of bitumen to specific requirements of each project such as characteristics of the substrate, traffic, loadings and weather conditions.

UL-M also has excellent durability thanks to the cohesion of the binders used and the gap graded formulations employed.

Use of a bond coat is critical to achieve a desirable thin surfacing application, says Mr Core. “The bond coat is an integral part of the UL-M thin surfacing system. It waterproofs the substrate and ensures the excellent bonding on which the long service life of the surface course depends. Poor bond at the interface can reduce a material’s life by 40%.

“Our UL-M thin surfacing system has been performing well globally for over 20 years. The design and quality of the material are carefully controlled and we pay close attention to how and where it is installed.”

Clearly one of the major benefits of specifying thin surfacing is that a material laid to a depth of 20mm will consume far less resource than if laid, for instance, to a depth of 40mm.

Thinly laid material will also reduce the quantity of surfacing that may need to be replaced later on, helping to reduce costs associated with future highway maintenance.

Email: info@jluk.co.uk

 

Long life demonstrated on M25

Thin surfacing has proved a success on the M25

Widening of carriageway on the M25 in Essex has led to replacement of a section of UL-M thin surfacing, 12 years after it was laid. “The surfacing was only designed to provide added texture to the motorway for four years and it lasted three times as long,” says Jean LeFebvre (UK)’s Jonathan Core.

Further north on the M1/A1 link a concrete section of carriageway was overlaid with UL-M thin surfacing just before the turn of the Millennium. It was installed to a depth of 20mm to reduce noise for the benefit of nearby residents. The section is still there to this day, adds Mr Core.

And in the capital, Transport for London’s maintenance contractor for the central region Ringway Jacobs has just specified a resurfacing of Park Lane using UL-M thin surfacing, a full 11 years after the same material had been installed along the route.

Twenty years of experience is set to be put to good use in the London Borough of Hounslow. VINCI Ringway has been named as the highways maintenance contractor for the council’s £800M 25 year Private Finance Initiative deal and is likely to make good use of UL-M to rejuvenate many of the council’s roads.

 

First use of UL-M in Staffordshire

UL-M was introduced to the UK by Alfred McAlpine and was first specified on the A34 Queensway in Stafford after a group of highway engineers from UK authorities visited France around 1992 to see new asphalt systems in action, including thin surfacing.

According to Alfred McAlpine’s former technical director Dennis Parkinson the dual carriageway site in Stafford was a great location for the UK’s first use of UL-M due to the range of issues that the thin surfacing product could address.

“The surface had previously been laid with Hot Rolled Asphalt and had begun to crack,” he said. “Location of joints in a viaduct over which the road crosses did not help the carriageway condition.

“A bus station nearby called for a surfacing material with high levels of skid resistance and a pedestrian crossing along the route demanded high friction characteristics. Added to this, the former HRA was proving noisy for some local residents when trafficked.

“Our system proved to be very robust and I am pleased with how the material performed. It has not had to be planed out since, only surface dressed on part of the site,” he added.

Staffordshire County Council’s former group engineer for major roads Jeff Farrington, who specified the material on the A34, said the thin surfacing has provided “extremely good service for an astonishing length of time”.

Part of the site has recently shown signs of distress, he added, “but at 18 years old, it has certainly given very good value for money.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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