Reappearing potholes are an all too frequent problem for local authorities throughout the UK, for which conventional repairs usually only provide a temporary solution. Heavy rain and sharp frosts this winter have increased the rate at which holes are appearing and at the same time have reduced the effectiveness of normal patching techniques.
What the country's road network is crying out for is a more permanent repair technique which would not only save time but also money. One contender is Jetpatcher - a machine that fills potholes and other road surface blemishes inexpensively and virtually on the run.
Jetpatcher repairs are officially categorised temporary but have proved long lasting. Now bitumen specialist Nynas is working with the Jetpatcher company to develop a more permanent repair for use in heavily trafficked areas.
The system is based on a selfcontained truck from which a large hose with a hand-operated nozzle delivers high volume air, aggregate and bitumen binder.
In action, a jet of air first removes the debris and moisture. Bitumen emulsion is then introduced into the air stream to seal any cracks or fissures.
Finally, the prepared cavity is filled with a mixture of aggregate and emulsion which hardens almost immediately.
The aggregate is mixed about 0.1 of a second before hitting the ground, with each particle evenly covered by emulsion as it passes through the spray nozzle.
The material is applied and compacted by the force of the air, layer by layer as it should be - from the bottom up not the top down.
Jetpatcher machines use cold lay technology which does not release emissions to the atmosphere and, because the repair is mixed as it is needed, there is no waste.
'The machine only needs a two strong crew, ' says Jetpatcher general manager Richard Jackson, 'one person to drive the truck, and another at the sharp end, to operate the nozzle.'
The aggregate used by Jetpatcher is usually a 6mm granite, grit stone or blast furnace slag, although stone size is variable from 3mm to 12mm depending on factors such as depth of fill, which can be up to 300mm.
Early trials concentrated on proving Jetpatcher's suitability for making good low grade roads. However, more recent trials have seen the machine used to repair higher grade roads which call for a very high performing bitumen binder.
Scottish company Tayside Contracts first tried Jetpatcher two years ago, initially on car parks and minor roads, for temporary repairs to last the winter.
However, these 'temporary' Jetpatcher repairs have continued to perform.
Tayside called on supplier Nynas to provide a high performance modified bitumen binder to enable the system to be evaluated on trunk roads.
'We set up trials in late 1999 on the A90 between Perth and Aberdeen, ' says Tayside Contracts works manager Ewan Duncan. The road carries a fairly heavy traffic load and, in common with many other Scottish roads, takes a fair battering from the elements. This presented a stiff challenge for Jetpatcher.
'Nevertheless, all the repairs we carried out are still intact, which speaks for itself, ' says Duncan. 'There is no tracking of the material and the system has stood up very well.'
Somerset-based Atmos Construction Services works manager Gavin Blogg is also an advocate of the system. 'We're very pleased, ' he says. 'We're happy with the unit rate, the price we pay per square metre of patch; and we're happy with the output that can be achieved. The repairs stand up very well indeed and we now consider that the system provides permanent repairs rather than temporary ones.