Mobile Asphalt Plants ready to take off

Engineers at Colas are preparing to take the firm's Ermont asphalt plant out on the road again, for supplying a programme of runway resurfacing projects at UK airports. The paving materials and contracting company is anticipating a busy 2008 in the airfields sector, following project successes over the past two years using innovative paving materials and its Ermont plant. Demand for similar work is gaining momentum.
Runways and taxiways at a number of UK airports are likely to be resurfaced by Colas this year, using airfield paving technology the company has introduced from France. The materials allow higher levels of asphalt laying productivity compared to traditional UK techniques and so have raised the need for high output plants such as the company's Ermont TSM225.

Over the past two years, the mobile plant has been used on the Shetland Isles and Tiree in the Inner Hebrides; projects which have shown materials developed to the French BBA (Beton Bitumeux Aeronautique) standard can be laid quicker than the Marshall Asphalt traditionally used in the UK. Airport operators are under pressure to maximise the availability of their runways and the demand is for greater durability, which brings a long term benefit for operators tghrough reduced frequency of maintenance.

"There has been a surge in interest from UK airport operators, in European materials, due to the now proven possibilities for reducing project time and extending the life of their runways," says Colas's airfields division business manager Carl Fergusson. "The mobile Ermont plant is just as suitable for producing large quantities of conventional asphalt for airfield and road surfacing projects, but the BBA materials have made very high outputs possible over a given time. This makes it economically viable to use the Ermont plant on airfield paving projects."
Colas's mobile plant, comprising material silos, mixing drum and generators, is transported on 11 trailers and, according to Fergusson, is the only one of its kind in the UK with a production capacity of 225 tph. It is also available for hire and further in its favour, the plant is connected up still standing on its trailers and very rarely requires construction of foundations before it is set up. "This takes only two weeks, from arrival to commissioning, so the plant is a huge help in planning terms and for getting to sites and starting work quickly," Fergusson says.

Colas first introduced BBA asphalt to the UK with the aid of its Ermont plant for the extension and resurfacing of Sumburgh Airport's main runway for operator HIAL (Highland & Islands Airports Ltd). This was no mean feat because Colas first had to demonstrate that the BBA asphalt mix would work when produced with the particular aggregates and bitumen to be used.

The BBA specification is more flexible than the Marshall Asphalt mix recipe approach; instead specifying materials to their required end performance. The French specification, however, requires aggregates and bitumen with particular high spec characteristics. Every BBA mix has to be designed to its specific constituents and then tested to prove the mix of ingredients will provide the necessary performance.

"We carried out the mix development work with help and advice from our CST (Campus for Science & Techniques) technical centre in France, with aggregates won on site at Sumburgh and bitumen from Nynas' refinery in Dundee," Fergusson says. "Mix design tests proved the required stiffness and other important performance parameters and the surfacing, once under way, demonstrated how much easier the BBA material was to manufacture and lay.

"We needed the Ermont plant because with the BBA mix, we could produce 200 tph and lay 200 m of surface course over the full 45m width of the runway in one shift. This was without cause for concern over correct compaction and air voids which can be the case with Marshall Asphalt."

That was in 2006 and was followed by HIAL asking Colas for a near repeat for resurfacing Tiree Airport's main runway last year. The Tiree work was similar, although this time with high spec aggregate from southern Ireland and an even greater test of planning and logistics to get materials and the Ermont plant to site on chartered and scheduled ferries.

All went well, according to Fergusson. With good planning and the Ermont plant's large bitumen and fuel storage sufficient to keep it running continuously through a 12 hour shift, Colas was able to lay more than 300 m of the 100 mm deep asphalt overlay between scheduled flights. The surfacing was finished during 21 working days in September 2007 and since then, representatives from UK airport operators including BAA have visited Tiree to inspect the results. There could be a lot of work in future for high output plants at UK airports.

Colas Ltd
Wallage Lane
Rowfant
Crawley
West Sussex
RH10 4NF
UK

T: 01342 711000
F: 01342 711099