A road surface engineering expert has warned of the prohibitive costs of maintaining roads in periods of extreme heat.
After a section of Yass Valley Way melted and disintegrated in 39+ degree heat last week, the Yass Valley Council attempted to arrest the damage by spraying water on the affected pavement.
Professor Frank Bullen, from the Faculty of Engineering at the University of Southern Queensland, said that putting water on melting bitumen is probably the worst thing that can happen. "They should put sand on it, not water," he said. "Sand will sink into the damaged pavement, where water will make it more brittle."
There is no alternative to bitumen as a surface for roads, but there is a lot of differentiation when it comes to bitumen types. Professor Bullen said that in straight run bitumen there are different grades to account for different climatic conditions.
Roads in this region have a “low softening point to save them from cracking in cold weather. This means that in extreme heat, they are more likely to melt than roads in, say, the Northern Territory where surfaces have a high melting point,” he said.
“A polymer-modified bitumen is superior to straight-run bitumen and has a very high brittle point, but is far more expensive.”
Professor Bullen said that the costs of maintaining roads as the climate warms are going to increase exponentially and that this will flow on to ratepayers.
According to Professor Bullen, many rural councils are allowing some roads to return to gravel as it's a lot cheaper to maintain them with a grader than it is to continue having to resurface them with bitumen. Perhaps the roads of the past are the roads of the future.