Total Bitumen’s Styrelf binder has been further developed to meet the needs of Tarmac Contracting as well as Transport Scotland’s TS2010 surfacing specification.
Asphalt designed to resist deformation in hot weather and prevent cracking at low temperatures has been developed jointly by Total Bitumen and Tarmac. The binder manufacturer joined forces with the asphalt supplier and surfacing contractor to create a new product that meets the demands of Transport Scotland’s TS2010 specification for highway surfacing.
Total Bitumen’s premium ‘Styrelf eXtreme’ range is used in high stress areas and, after many months of product development, presents a solution for TS2010. “We have developed a binder that is more flexible than ever before,” says the company’s Market Development Manager Rick Ashton. “Our binder has been developed to meet TS2010 but has also been rolled out on contracts across the UK since the spring.”
As a result, Tarmac’s stone mastic asphalt surfacing using ‘Styrelf eXtreme’ binder has been laid this year on sections of the Scottish road network including the M8 and the Clyde Tunnel – and is soon to be specified on an approach to the Forth Road Bridge.
A performance assessment of sections laid to meet the TS2010 specification will take place after two years to monitor skid resistance.
Development of Styrelf eXtreme allows Total Bitumen to demonstrate that a binder modified with advanced polymers can increase the temperature profile in which material performs to a high standard. The binder is elastic, resists extremes of temperature at both ends of the scale and remains flexible without being too stiff.
“Historically there was a focus on creating asphalt with high stiffness but there is now a realisation that higher levels of flexibility can be more desirable in certain applications,” says Mr Ashton. “This is especially important when an asphalt overlay is specified to resist reflective cracking caused by a cracked concrete foundation or where there are expansion joints in a carriageway. By using advanced polymers we can allow an asphalt to be both flexible and durable.”
The binder’s high resistance to deformation makes Styrelf eXtreme particularly suited to Scottish roads, Mr Ashton adds, where there have been concerns about brittle surfacing products cracking at low temperatures. “The ability of the binder to resist softening in hot weather can also help safeguard against extreme weather events,” he adds.
Total Bitumen reassessed its polymer modified bitumen range three years ago and Styrelf eXtreme forms part of a new portfolio of recently developed binders. The origins of the bituminous material can be traced back several decades to when earlier versions of Styrelf were specified on schemes in continental Europe and around the world.
“The Total Group has significant experience of using ‘cross linked’ polymer modified binders notably in Germany and France on roads, in tunnels and on bridges,” says Total Bitumen’s National Sales & Marketing Manager John Tuite. “We liaised closely with technical teams in both countries before our Preston based Technical Centre developed our latest version for the UK market. “Previous experience of using Styrelf on bridges in Hamburg provides us with confidence for our Styrelf eXtreme solution.”
The A1 highway bridge near Hamburg, for instance, was surfaced in Styrelf in 1984 and remained in place until 2008 – a 24 year service life compared to a six or seven year design life using conventional surfacing. Use of Styrelf binder reduced maintenance costs and most importantly, Mr Tuite adds, reduced disruption to the travelling public.
He also points to results of an academic study carried out by Lausanne University in Switzerland, where independent research showed Styrelf to be one of the best performing polymer modified binders in Europe. The study focused on ageing performance and how the binders stand up under extremes of temperature. A section of asphalt containing Styrelf had no cracking and had not required resurfacing in over 20 years.
Specifying a binder that extends the intervals at which highway resurfacing is required also demonstrates a sustainability benefit, adds Rick Ashton. “Some people may think that recycled materials constitute sustainability,” he says. “But sustainability is also about creating products that last longer compared to previous materials which in turn leads to less maintenance and disruption.”
Going forward Total Bitumen expects that Styrelf eXtreme will become a universal binder for a wide range of applications where enhanced durability of asphalt is required, especially where existing strata or foundation is of a variable quality.
Binder performs well on several sites
Styrelf eXtreme proved its worth recently when used as part of Tarmac’s Masterlayer HD20 surfacing on the A169 at Saltergate Bank in North Yorkshire. Surfacing was laid to a depth of 70mm to renew asphalt laid over a sub base of variable quality.
“We previously recommended use of a heavily modified Masterlayer for schemes where the client wanted a durable yet flexible product to increase the structural stability of roads without the need for complete pavement reconstruction,” says Tarmac National Contracting’s Technical Manager Ian Carr.
“Our client Ringway, working for North Yorkshire County Council, selected Masterlayer as the most appropriate solution. The paving gang found the material to be easy to work with.”
Elsewhere, Styrelf eXtreme has been specified as part of an asphalt overlay on the slip roads to the Clyde Tunnel in Glasgow. Deteriorated concrete foundation had caused problems with the surface.
A conventional thick overlay was not an option because existing levels could not be altered. Around a thousand tonnes of 50/10 and 60/20 Hot Rolled Asphalt binder course was applied as a regulating treatment followed by 900t of Masterlayer S 10mm Surface Course containing the Styrelf eXtreme binder.
“This treatment was applied to resist further reflective cracking with the aim of extending the design life over previous installations,” explains Tarmac Technical Manager for Scotland Gordon Hogg.
Around 1400t of Tarmac Masterflex using Styrelf eXtreme was also installed this year on the M8 near Edinburgh. “Tarmac and Total’s joint technical development of Styrelf eXtreme binder gives us confidence to use this binder in the Tarmac product portfolio on such schemes,” adds Mr Hogg.
And Tarmac and Total have a TS2010 scheme, about to start on the approach to the Forth Road Bridge near Edinburgh. Again Tarmac’s product will be used with Styrelf eXtreme binder to comply with the new SMA specification.
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