This month, mainstream media has been inspired by stories of self-healing asphalt from researchers at Kings College London and Swansea University.
“'Self-healing' roads aim to solve pothole crisis,” said a headline on the BBC news site.
This excitement could be a little premature, however, as the research is still in its early stages. The basic idea is that tiny spores or microcapsules contained in the asphalt, break open to release rejuvenator – which could be derived from algae or recycled cooking oils – into the bitumen, softening it so that it can heal up cracks.
The AI, in the form of machine learning, comes in because it vastly increases the capacity for computational modelling. In this case, modelling can help to look at what is going on at an atomic level in bitumen when oxidisation occurs leading to hardening and cracking.
The researchers have conducted laboratory experiments with the technology. They report that surface microcracks in bitumen containing the special spores healed in less than an hour.
Self-healing asphalt isn’t a new concept. In the Netherlands, they built their first self-healing road back in 2010 and have laid several more trial sections since. The brainchild of micromechanics expert Professor Erik Schlangen from Delft University of Technologies, these roads contain tiny steel fibres. Special vehicles drive over the road to heat up the fibres by induction, causing the bitumen to melt and heal up the cracks. Researchers found that doing this at four-year intervals gave the best results.
Researchers at Delft have also looked into the use of microcapsules containing a rejuvenator, such as waste cooking oil, which crack open to release their contents, helping microcracks in the asphalt to heal. This process was also trialled in Granada, Spain, when contractor Acciona has laid a road containing microcapsules of rejuvenator from Repsol.
Of course, there is a downside to these potential self-heal technologies: the capital cost of the asphalt will be higher. Researchers in the Netherlands estimated that asphalt containing steel fibres could be around 25% more expensive than standard stuff. Although, over the lifetime of a road, their use would lead to significant cost savings.
So, we can’t expect self-healing roads to magically heal up potholes or even large cracks. But they may be a way of keeping potholes at bay for longer – just like the road surface treatments discussed in our last blog.
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Thermal Road Repairs: Decarbonising the asphalt repair industry
High output. Low emission. Zero waste. Permanent solution
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