Road construction in Canada’s northern regions presents the challenge of building on soil that remains frozen throughout the year, otherwise known as permafrost. Conventional black asphalt absorbs the sun’s rays and the resulting heat melts the permafrost, leading to premature surface deterioration and deformation of the road.
When Dawson City decided to pave Front Street, it was looking for an alternative to black asphalt to avoid melting permafrost and to maintain the city’s historic character. Dawson City was a gold rush boom town more than 100 years ago and today its main economic industry is tourism.
It was decided that Bituclair®, a product designed and manufactured in France by Colas, would meet the demands of the project. Bituclair® is a synthetic binder similar to bitumen, but without the black colour. Due to its capacity to accept a pigment, Bituclair® allows pavement to be produced in a lighter colour. This would be the first use of Bituclair® in North America.
For this job, a 75-millimetre layer of conventional bitumen asphalt was laid on Front St., which was then overlaid with a 25-millimetre layer of Colclair® (the combination of Bituclair® and aggregate). Paving was completed on September 20th, 2009. In all, 4,900 metric tonnes of conventional black asphalt was used and 1,900 metric tonnes of Bituclair®. The final road appearance is a neutral grey colour that results in less heat absorption.