29 Jun 2022

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A new approach to maintaining Christchurch’s asphalt roads could offer a win for the environment and for the city’s road users.

“Asphalt is a great surface for roads, but as it ages it loses oils and resins, which causes the surface to become brittle and break apart,’’ says Christchurch City Council City Streets Maintenance Manager Steve Guy.

“We spend on average $3 million each year milling out brittle asphalt and replacing it. With the rising cost of materials and an ageing roading network, this works out to be approximately 25 kilometres renewed each year.

“We have 584 kilometres of asphalt roads across the city which means that, based on our existing budgets, it would take us about approximately 23 years to resurface the whole network. It is not a sustainable option to carry on doing what we are doing without increasing our budgets, so we have sought out new technologies that allow us to rejuvenate our roads, rather than waiting until we have to replace them,’’ Mr Guy says.

“By applying a rejuvenation seal to asphalt 10 to 15 years after it is laid, you can replace the oils and resins that have been lost due to ageing. The product sinks down into the asphalt and counters the effects of ageing by filling in minor cracks, creating more elasticity and waterproofing the road surface (best described as ‘collagen for roads’).

“It can extend the life of an existing surface by between 6 - 10 years, so it is a worthwhile investment to make. In the coming financial year, we are not only planning to replace the same amount of old asphalt, but also rejuvenate an additional 22.6 kilometres of asphalt,’’ Mr Guy says.

“This rejuvenation work will be funded through existing maintenance budgets, so no additional funding will be sought. It also means that we will be nearly doubling the amount of work being done on asphalt roads around the city. This should lead to better road conditions for all users.’’

Mr Guy says rejuvenating asphalt where possible not only makes financial sense, but is also good asset management and better for the environment.

“It means we can reduce the number of times we mill out a road, which in turn reduces the amount of material that we need to dispose of at landfill.

“Less material being sent to landfill means less truck movements, which means less impact on residents, in turn resulting in lower fuel requirements and reduced emissions.

“By rejuvenating rather than replacing asphalt we are also reducing the need for materials to be supplied by quarries so that is another factor in its favour,’’ Mr Guy says.