It pays to repave in colder climates
Repaving roads is a costly and complicated process, especially when the road is a critical artery. But new research from Norway shows that switching to more durable asphalt could save significant amounts of money on some cold climate roads—possibly as much as several million euros a year.
Sara Anastasio, a researcher at the Norwegian University of Science and Technology's (NTNU) Department of Civil and Transport Engineering, believes it would pay to replace the asphalt on Norway's busiest routes with a different type of paving.
Professor Inge Hoff from the same department also believes it may be appropriate to replace the asphalt on stretches where there is less traffic when the climate is a factor for durability.
"But this is a very complicated topic," Anastasio says.
Anastasio has shown that precipitation plays a major role in pavement durability. Studded tires are also a factor, whereas salt does not affect the roadways as much as previously believed.
It is difficult to calculate the possible savings precisely. But this year NOK 1.2 billion has been budgeted for replacing the pavement on national highways alone. Municipal and county road upgrades are in addition to this.
"We're talking maybe about NOK 2 to 3 billion for laying new pavement each year," Professor Hoff estimated.
By extending pavement life by an average of 10 per cent, which corresponds to a year or two, NOK 200-300 million could be saved annually. This is a rough estimate, since a lot of factors come into play.
Asphalt is not the only critical factor. Especially on older stretches, the substrate contributes to how quickly the road wears down. If the substrate quality is poor, replacing just the top layer of asphalt offers less benefit.
Water is the most destructive force
Anastasio is an asphalt expert and currently works as a postdoctoral researcher at NTNU. She defended her doctoral dissertation on 28 May 2015 and has been researching various materials that can be used for road surfaces.
She makes materials. Then she destroys them. "You have to find the right balance," she says.
Anastasio has won the researcher of the year award in the Nordic Road Association competition for her work with various asphalt mixtures.
Her research shows that water is one of the most destructive elements to pavement. Precipitation destroys its composition, but it is not the only challenge for road construction in Norway.
"Asphalt can last for 20 years, but it needs to be maintained," says Anastasio.
The total length of Norway's public roadways in 2008 was around 93,000 kilometres, in addition to 126,000 kilometres of private roads. All this needs to be kept up by Norway's population of just under 5.2 million inhabitants. Even with recent increased maintenance, the country still has considerable catching up to do.
Paving roads in Norway brings challenges that other countries do not need to worry about, including extreme temperature variations. In winter, temperatures often dip to -20° or even -30° C in several places. Summer brings temperatures of 20 to 30 degrees above, and the asphalt gets even hotter, often 50-60 degrees.
Studded tyres – again
Many Norwegians drive around with studded winter tyres to compensate for the icy, hilly roads.
"You can see the damage to the pavement in winter. It's mostly due to studded tires," Anastasio says.
Anastasio has also found that salt is not as bad as previously thought, but since salt causes more humid conditions, it also indirectly corrodes the pavement.
Few asphalt researchers around
Anastasio knows that she will not be able to find an ideal asphalt solution for Norwegian conditions on her own. She is one of the very few asphalt researchers in Norway. That is precisely one of the problems.
Many people want improved roads, but at the same time it is also important to find asphalt that is better suited to withstand the unique challenges found in Norway—hence the need for further research. The Norwegian Public Roads Administration and Avinor AS have sponsored Anastasio's doctorate. But asphalt researchers would like to see more bright minds working on this issue with them.