Wherever there are roads, there are potholes – we’ve come to accept it as a given. But a recent development out of the UK might make it possible to have the former without the latter.
Sunflower oil is known for being good for human health, and a recent innovation by a researcher at the Nottingham Transport Engineering Centre (NTEC) in the UK could see it being used to eliminate potholes and extend the life of roads as well.
The heavy loading caused by vehicles on asphalt roads can cause cracks in their surface. This is known as fatigue cracking, and can be more severe if the road’s base is weakened by factors such as poor drainage, or if the aggregate (gravel or sand) layer beneath the top layer of asphalt is dislodged because it does not stick to the asphalt well enough. Fatigue cracking generally increases with the age of a road, as the asphalt binder becomes less flexible over time.
To solve this issue, Dr Alvaro Garcia and his research team have developed microcapsules of sunflower oil that can be added to the asphalt used in road surfaces. If the road cracks, the capsules break open and release the oil, which lowers the viscosity of the asphalt binder on either side of the crack. This makes the asphalt sticky and soft enough to repair the local damage and prevent it from worsening.
According to Garcia, the mixture of asphalt and sunflower oil capsules, known as Capheal, could extend the working life of a road by around four years without significantly increasing costs or decreasing the road’s strength.
“Our preliminary results showed that the capsules can resist the mixing and compaction processes without significantly reducing the physical and mechanical properties of asphalt and they also increased its durability,” he said.
“More importantly, we found that the cracked asphalt samples were restored to their full strength two days after the sunflower oil was released.”
Garcia said that other advantages of this technology are that it reduces the need to mix healing agents in bulk, as it is activated only where cracks occur. And unlike self-healing roads in Europe, which incorporate metal fibres and use induction heating machines to melt the bitumen to fill in cracks, Capheal does not require heavy machinery or road closures.
Next steps will see the NTEC team embedding Capheal on sections of road set to undergo maintenance work. This will be followed by a monitoring period of 12 to 24 months to determine Capheal’s durability and endurance under real-world conditions.