Quick Dips

Better and Cleaner Roads

A laboratory-based instrument built by two Hutt Valley researchers could lead to more chipseal being used on New Zealand roads, rather than expensive asphalt.

"Chipseals are much cheaper -- five to six times -- than the alternative, asphalt," says researcher Phil Herrington, of Opus Central Laboratories. "Essentially, our work could save Transit New Zealand and local authorities quite a bit of money, which can then be diverted into other roading projects."

The instrument simulates how vehicles' braking and cornering can damage road surfaces. It is basically a trolley to which a tyre or rubber pad is attached and rubbed against a sample chipseal road surface. The pressure is increased until the chipseal dislodges from the bitumen that binds it and holds it to the road.

"It measures friction by sliding a chipseal test surface relative to a fixed specimen, which can either be a rubber pad or a tyre," Herrington says. "Although it's fixed, the tyre can be turned at different angles to the sliding test to simulate cornering."

He says the problem on many New Zealand roads is the strength of the bitumen that binds the chipseal and sticks it to the road surface.

"We have been working on ways to measure and ultimately to improve the strength of chipseal surfaces so that they can be better used in high-stress areas," he says.