Capsules mixed with asphalt could be used to ‘self heal’ potholes on our roads


A trial is underway led by Highways England which uses sunflower oil to help prevent potholes by ‘self healing’ and filling in any dents and cracks in the road.

Sunflower oil capsules mixed with asphalt has been found to make roads ‘self heal’ and could be a cheap solution to our pothole problem here in the UK.

It’s estimated that the cost to fill in potholes up and down the country is over £88million per year, so using cooking oil which only costs about £1.15 for a litre bottle in the shops is a fairly cheap solution to the huge problem.

Capsules mixed with asphalt could be used to 'self heal' potholes on our roads

Could sunflower oil be the new weapon to fight the pothole problem here in the UK? © Copyright Jaggery and licensed for reuse under this Creative Commons Licence.


The bitumen is made less thick so it can be poured easier into the cracks on the road before they turn into dangerous ditches.

The sunflower oil was sourced from a local supermarket by engineers at the University of Nottingham, who discovered that capsules don’t make road surfaces less durable or more slippery which is what they were initially fearful of.

However, what the capsules actually do is enable the asphalt to ‘self heal’, which means roads don’t have to be closed whilst holes get filled in.

The research has been funded by Highways England, who will add 18.5 litres of sunflower oil to 5 tonnes of asphalt which stretches five-yards to test if it works.

According to researchers, if the trial is successful, the ‘self healing’ technology could be introduced across the UK road network within five years.

“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,” said Senior author Dr Alvaro Garcia from the faculty of engineering at the University of Nottingham.

When using bitumen only to fill in cracks on the road it takes around two to three days for the work to be carried out, plus roads have to be closed. By adding sunflower oil, the process will take around four hours to complete and roads won’t have to be closed whilst the work is carried out.

The sunflower oil capsules can sit in the road surface for years and will only break open when the build-up of traffic pressure gets to a point where cracks start to form.

The capsules contain sunflower oil which measures one tenth of an inch (2.9 millimetres) and uses calcium and an emulsifier to provide them with a hard shell.

According to researchers, the oil used to help ‘stick’ the asphalt back together could mean the lifespan of a road is increased by around a third, from 12 to 16 years.

When the technology was used on asphalt, the material recovered over half of its original strength, compared to 14% without the capsules.

It’s believed this study is the first ever to successfully use sunflower oil to mend asphalt.

“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,” said senior pavements adviser at Highways England Robin Griffiths.


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