Sunflower oil is being used to prevent potholes by filling cracks in the road.
Highways England is carrying out a trial, after sunflower oil capsules added to asphalt were found to make roads ‘self heal’.
It costs more than £88million a year to fill in the potholes in England’s roads, making the cooking oil – at around £1.15 a litre in shops – a relatively cheap solution.
It works by making bitumen, the sticky black substance used in road surfacing, less thick so that it pours more easily into cracks before they form the dangerous trenches.
Highways England is carrying out a trial using sunflower oil to help the nation's roads self heal
Engineers at the University of Nottingham, who sourced their sunflower oil from a local supermarket, found the capsules do not make road surfaces more slippery or less durable as feared.
But they do allow asphalt to ‘self heal’, delaying the need to close roads and fill in holes.
Highways England, which funded the research, will add 18.5 litres of sunflower oil to five tonnes of asphalt along a five-yard stretch to ensure that it works.
Engineers at the University of Nottingham, who sourced their sunflower oil from a local supermarket, found the capsules help asphalt repair itself
Researchers say, if successful, it could be rolled out across the road network within five years.
Senior author Dr Alvaro Garcia, from the faculty of engineering at the University of Nottingham, said: ‘You could use any oil and have the same effect, from motor oil to recycled cooking oil, although sunflower oil is very cheap.
‘This solution allows roads to repair their own cracks of up to half a millimetre width in a matter of hours, which bitumen alone could not do.
‘We are tremendously excited about these self-healing properties and can see a future free of potholes and road maintenance.’
Potholes form after sunshine causes roads to swell, before night-time temperatures fall and they contract.
The weight of the traffic as this happens causes cracks to form, which become larger when rainwater falls into them, freezes and expands.
Bitumen, the viscous material taken from tar or petrol which helps make up asphalt, can fill these cracks, but takes two to three days to do so and only when a road is shut and has no traffic.
When capsules are added to the asphalt, they allow it to 'self heal' which could provide a much cheaper way of filling potholes
Sunflower oil speeds this process up to four hours, by making the bitumen less thick and better able to flow. It is expected to do so even with traffic on the road.
Dr Garcia was inspired by the Spanish version of the television show Masterchef, where he saw oil ‘spherified’ into small globes like caviar.
He used the same technique to create capsules of sunflower oil measuring a tenth of an inch (2.9 millimetres), using an emulsifier and calcium to give them a hard shell.
The capsules can remain in a road for many years, but break open only when the build-up of traffic pressure reaches the point which causes cracks.
Researchers say the oil, which ‘sticks’ the asphalt back together, could increase a road’s lifespan by at least a third - from 12 to 16 years.
When used on asphalt, the material recovered more than half of its initial strength, compared to 14 per cent without the capsules.
The study is believed to be the first to successfully use sunflower oil to repair asphalt.
The cost of filling potholes across England costs more than £88million a year, with 1.7million filled in Britain over the last year
Dr Garcia previously worked on using metal fibres to melt bitumen and fill in road cracks, but this requires a large and expensive induction heater.
The Asphalt Industry Alliance, which puts the cost of filling England’s potholes at £88.3 million a year (SUBS – PLS KEEP), says more than 1.7million have been filled in Britain over the past year.
However, covering the entire road network would require 82,000 tonnes of sunflower oil.
Robin Griffiths, senior pavements adviser at Highways England, said: ‘We know road users want good quality road surfaces, with fewer potholes and not as many roadworks disrupting their journeys.
‘This self-healing technology could give them that and offer real value for money.
‘So far the Nottingham University research we have funded is showing real potential in how easy it is to mix and apply, as well as being sustainable and environmentally friendly.
‘Now we have to test the material on small patches of road, to see how it copes with the stresses and strains of daily traffic and the British weather.’