The new weapon against potholes? Sunf lower oil!

SUNFLOWER oil is being used to prevent potholes by helping to fill cracks in the road.

Highways England is carrying out the unusual trial after sunflower oil capsules were found to make roads ‘ self heal’ when added to asphalt.

It costs more than £88million a year to fill in the potholes in England’s roads, making the cooking oil – which costs around £1.15 a litre – a cheap solution.

The capsules work by making bitumen, a sticky black substance used in road surfacing, less thick so that it flows more easily into cracks before they form the dangerous potholes.

By adding them to asphalt, the capsules can remain in a road for many years – breaking 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, and mean roads do not have to be closed for repairs. Engineers at Nottingham University found the capsules do not make road surfaces more slippery or less durable.

Highways England, which funded the research, will add 18.5 litres of sunflower oil to five tonnes of asphalt along a fiveyard stretch. If successful, the scheme could be rolled out across the road network within five years, researchers said. Dr Alvaro Garcia, from Nottingham’s engineering faculty, said: ‘You could use any 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.’ Potholes form after sunshine causes roads to swell, before night-time temperatures fall and they contract. The weight of traffic as this happens causes cracks to form, which become larger due to rainwater.

Bitumen, found in asphalt, can fill these cracks. But it takes up to three days, and only works when a road has no traffic.

Sunflower oil speeds this process up to four hours by making bitumen less viscous. It is expected to do so even with traffic on the road. Dr Garcia was inspired by a Spanish cooking show that ‘spherified’ oil.

The Asphalt Industry Alliance puts the cost of filling England’s potholes at £88.3 million a year.

However, covering the entire road network would require 82,000 tonnes of sunflower oil.

In 2016/17, Highways England invested £626 million renewing our roads. Based on this, researchers say sunflower oil could cut the annual repair bill by £260 million. Initial tests of the 2.9mm oil capsules would be on carefully selected patches of road, which would be monitored for one to two years before a second test on a longer stretch.

‘Repair their own cracks’