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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 shap 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 self-contained 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 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 providing Jetpatcher's suitability for making good
low grade roads. However, more recent trials have see 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 c ar
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.
More information
can be obtained from 'New Civil Engineer, March 2002'.
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