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Highways - Level best

Resurfacing - Asphalt has got thinner and quieter during the last decade and looks set to be laid wider and smoother too thanks to new paving technology.

Performance demands on road surfacings are becoming ever greater as traffic volumes increase and highway authorities seek to maximise the life spans of carriageways.

Until recently, the road construction industry has mainly looked to materials innovation, but focus is now shifting towards hi-tech laying processes.

'The next significant change will come from improved laying techniques, ' confirms RMC Surfacing director Martin Stevens.

RMC is finalising negotiations with the Highways Agency to resurface part of the M5 and the contract is likely to feature use of a laser guided paving system. The section runs over several viaducts which means that the weight, and hence thickness, of the final surfacing solution is critical.

'Many older concrete viaduct decks have inherent variations in level, ' says Martin. 'Laser guided pavers can automatically adjust the surfacing thickness which makes attaining a smooth finish easier.

'Improving surface regularity creates a better ride for road users, and helps cut fuel consumption and road noise.

And fewer ridges in the road means that there is less potential for axle bounce, so the carriageway is put under less stress. The pavement will last longer.'

The computerised paving system which RMC plans to use has automated slope and grade controls and is linked, by laser, to an independent total station.

The paver's on-board computer continuously compares design data with actual position data received from the total station, making the tiny adjustments necessary to create an even pavement.

RMC's plans for the M5 are still under development, but it showed what can be achieved using new equipment when it resurfaced both lanes of a 2km stretch of the eastbound M50 earlier this year. Work was carried out in a single pass using an extra wide paver in just 12 hours - a quarter of the time needed by conventional machines.

The screed on the paver was fitted with specially designed extensions to allow it to surface the 8.5m wide carriageway with a 40mm thick layer of RMC's Viatex thin surfacing.

Long term advantages of wider paving come from the elimination of longitudinal joints from the trafficked section of a road. Joints are always the weakest part of a road surface, no matter how high the quality of the asphalt or however carefully controlled the laying process. Most carriageway failures are caused by water ingress through joints and minimising or removing them will reduce the need for unplanned maintenance.

Another piece of equipment which RMC hopes to introduce to the UK soon will help reduce transverse joints and promote improved surface regularity.

Shuttle buggies - machines which can ferry asphalt from delivery wagons to the paver - allow paving to become a continuous process.

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