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SLIPPERY ROAD

The carbon footprint of road maintenance could be about to change, thanks to an inventive use of vegetable oil.

It looks like refined crude, but the bag of viscous fluid on the desk of Colas UK business manager Carl Fergusson does not contain a single hydrocarbon from refining oil.

Vegecol, as Colas has called it, is an entirely vegetable based alternative to bitumen and petroleum resin binders and so carries massive potential for the pavement sector.

For highway authorities and other clients it could mean a massive reduction in energy consumption and a decoupling of projects from rising crude prices.

Use of this new material allows an asphalt mix temperature as much as 40 degrees centigrade lower than the norm, meaning lower fuel consumption and fume emissions at the plant. Asphalt made with Vegecol does not degrade when in contact with fuels because it does not contain hydrocarbons.

Colas UK's parent company, Colas SA, manufactures the binder at Vitrolles in France and is guarding the secret of its manufacture, although the French patent gives the material's constituents as "purely natural or modified natural substances of agricultural vegetable origin".

In Europe, use of Vegecol has extended to surface and base course asphalts and the Vitrolles plant is now producing the binder at a rate of about 1, 000t per year. According to Fergusson, it is for use wherever bituminous binders are normally used.

Colas has recently used Vegecol as the binder in a UK pilot project, resurfacing a footpath in Portsmouth. It is a "transparent" binder and so produces naturally aesthetic or coloured asphalts with the addition of decorative aggregates or pigment.


"The UK target market is initially heritage sites and local authority and private sector estates, but ultimately, anywhere bitumen is used, Vegecol can be used instead," Fergusson says.

"We have already carried out surface dressing in Germany with it as the binder, and surface and base course asphalts have been developed and laid in Belgium, Hungary and Martinique. It has also been used as the binder in an insitu asphalt recycling process."

In Portsmouth, coloured asphalt containing Vegecol has been used to resurface footpaths in Jack Cockerill Way, through Colas' 30-year PFI road maintenance contract with the city council. With only a relatively small amount needed for the scheme, the binder was delivered in 1kg bags.

"This was less than ideal for handling, but everything else with regard to the asphalt production, bar the lower temperature, was as normal with conventional mix and laying plant used," says Colas technical manager for asphalt and quarries, Steve Cant."The usual precautions with clear or coloured mixes regarding cleaning of equipment must be taken, but the work in Portsmouth was based on a standard asphalt mixture. We just replaced the bitumen binder with Vegecol and added pigment to get a deep red colour, although with a vibrantly coloured aggregate no pigment would have been necessary.

New UK asphalt standards harmonised with those in Europe came into force this month with CE Marking of products.

"The CE Mark serves as an assurance of quality, that the material has been produced to documented and auditable factory control procedures and type tested for performance-related properties," says Colas technical development manager John Richardson. "Vegecol is subject to a similar type of assessment and control, but there is no provision for its use in the harmonised standards."

How asphalt containing Vegecol is specified in the UK will depend on the client. Approval of departure from standard will be needed for many public sector roads because asphalt standards only talk of bituminous binders, which this, of course, is not.

"However, for private sector clients, we can also back up Vegecol with test data and a long list of examples of its use," Richardson says.

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