Despite much noise and bluster, innovation in the UK road surfacing sector is in short supply. Why? New Civil Engineer investigates
The UK road surfacing sector is not doing that well in terms of innovation, despite admirable technology focused research being carried out by Leeds University-led consortuims and others.
Some of this is to do with the sector’s loss of credibility in recent years. Stone mastic asphalts (SMAs) and thin surfacings – relatively new technologies lauded as pioneering examples of pavement engineering – have failed to live up to expectations, service life often being half that claimed. Clients have grown wary.
Another factor is lack of research.
There is little return on investment in surfacing research and development (R&D), so private companies are generally reluctant to back speculative projects with money.
The government is no help. Funding announcements seem to be more about smoke and mirrors than actual budgets. Transport secretary Chris Grayling’s announcement in January of £22.9M “for research and trials of new surface materials (and) pothole repair techniques” is a case in point.
Focus on the fine print and it becomes clear only £1.6M will go directly on surfacing – to extend a trial of “plastic roads”.
But not all is doom and gloom. “It’s the nature of innovation for older ideas to be reinvented to suit new situations,” says Colas technical head John Richardson.
He points to a study to develop long life surfacing for Highways England which involved Colas and is now with Highways England to assess.
Epoxy asphalt is not new, it was developed long ago specifically for bridge decks. Its potential as a surfacing material for long life roads – lasting for 30 years and more – is now deemed to be high.
“Roads of epoxy asphalt would be stiffer and more resistant to rutting, low temperature cracking, surface abrasion and fatigue cracking,” says Richardson. “Also less susceptible to water-induced degradation such as potholes.”
Thin surfacings are being reinvented as sound deadening overlays to concrete pavements and have also been modified to allow cold applications.
Among local authorities, there is increasing enthusiasm for refurbishment rather than renewal.
There are systems to seal existing surfaces to extend life and others which incorporate rejuvenated old bitumen. Some are “old” innovations that are being developed and promoted to increasingly receptive clients.
Preservative and rejuvenation materials such as Colas’ PenTack system and ASI’s Rhinophalt are claimed to extend the service life of asphalt pavements by up to six years.
Surface dressing developments include “fog sealing”, where a mixture of high performance bitumen emulsion and aggregate is used to lock in chips or to coat a new hot mix surface to lock in fines and fill surface voids.
Meanwhile, independent trials are already backing up claims that waste plastic can have the performance enhancing effects achieved by expensive polymer modified bitumen when added to asphalt mixtures. The government has recently awarded £1.6M to further this research and produce a guidance document.
“We’re really pleased that our message is getting across,” says assistant director, economy and environment, of Cumbria County Council Stephen Hall. “We’re producing asphalt, we believe, of high durability and comparatively low cost, which also provides considerable environmental benefit.”
Cumbria is conducting trials at five sites of varying nature in terms of loading, the latest along the single carriageway A7 into Carlisle. A 450m long plastic modified asphalt section has been trafficked for the last 12 months with no sign of deterioration.
“Altogether we’ve laid about 1km in length of trial road – using the equivalent of a staggering 6.5M single use plastic bags,” Hall claims.
The waste plastic is added to asphalt mixtures as pellets processed by the local firm of McRebur.
With the latest funding, Cumbria and McRebur will be joined by the universities of Nottingham and Central Lancashire plus Australia’s Sunshine Coast University and the University of California. Accelerated life testing and end of life potential (ie recycling) will be priorities.
Future of Highways Maintenance | Sound and fury