BLOG: Self-healing roads

The huge increase in car sales over recent years has lead to there being nearly 1.2 billion cars in the world.[1] Despite the increment of new technologies implemented by manufacturers, the dangers that drivers and passengers face when they hit the road remain far from ideal. According to recent research carried out by the World Health Organization, each year more than 1.2 million people die due to road accidents.[2] Why is this number so large? One of the main reasons is the bad state of the roads, in both developed and underdeveloped countries. For instance, potholes have caused nearly 1200 deaths in India over the last 4 years.[3] In addition to this, according to recent research, the bad state of roads may be the cause of one third of road accidents in the USA.[4] Plenty of solutions have been suggested with the aim of solving this issue. Among them, self-healing roads are one of the most promising.

Today, most roads are built using a rather simple approach that has been in use for a long time: a mixture of bitumen and small rocks,[5] most commonly known as asphalt. The main advantages of asphalt are the cost, the fact that it works well, and that it reduces the vibrations (and thus the noise) that cars produce. Vibration is reduced because the asphalt has small holes, which allow air pressed down by the tyres of a car to find other exit pathways, thus reducing the soundwaves produced.[6] These advantages make it difficult to compete with. However, its main disadvantage is that big potholes and cracks can be created easily, due to water or erosion created by cars and motorcycles, and the fact that maintenance can be expensive.[7]

Figure 1: Illustration of the self-healing road developed by the Delft University of Technology. A magnetic inductor is added within the layer of conductive asphalt (i.e., asphalt mixed with conductive fibres) to enable the mixture to flow to cover any gaps that begin to form in the road.

One of the most developed concepts that currently competes with asphalt (by overcoming its main disadvantage) comes all the way from the Delft University of Technology in the Netherlands. According to recent research done by Prof.dr.ir. E. (Erik), creating a self-repairing road is viable. In this case, the clever approach makes use of the already used mixture for roads, with a little twist. Conductive fibres are added to the mixture of bitumen and small rocks.[8] Thanks to these fibres, whenever the road starts to crack, the mixture will start to flow (by magnetic induction) and cover the gaps, thanks to the magnetic charge of the mixture. This technology is already in use in twelve roads in the Netherlands.[9] According to the University of Delft, by using this type of technology, the government of the Netherlands could save up to 90 million[10] euros a year, thanks to the reduced maintenance costs. Moreover, the technology can be further developed by taking advantage of the conductive fibres. The idea is that electric car batteries will be able to charge while they are on the road, via wireless charging.[11]

One of the biggest drawbacks to this technology is that it’s not a hundred percent self-healing, as it needs magnetic induction to heal. So far, however, the issues encountered with normal asphalt have not been encountered in the existing self-healing roads of the Netherlands. Although this is good news, they require testing for a few more years to determine whether the product works or not as normal roads would be in the same condition within that timeframe.

As road safety is a big issue in our society, there are other a variety of competing solutions currently in development. For instance, scientists from the university of Nottingham Transportation Engineering Centre[12] found a way to create self-healing roads using a rather unusual approach. Taking inspiration from the famous cooking show MasterChef, they came up with the idea of using spherification. The idea behind this project is to create spheres of sunflower oil in the road. As time and cars pass by, and cracks begin to form, the bubbles break and the liquid starts covering the gaps and putting the road back together.[13] Despite being a promising idea, this technique—quite common in high-standard cooking—has not yet been tested outside the laboratory.

If self-healing technology begins to find broader use, the improvements in road quality would be substantial. There are a number of advantages to the implementation of self-healing roads, not leads reduced traffic congestion, thanks to the reduced need for maintenance. Furthermore, if the idea of wireless car charging is realised, electric cars would become much more common as their main problem (i.e., range) would be resolved. As a result, less pollution would be created, driving us to a cleaner future.

References

  1. J. Voelcker, 1.2 billion vehicles on world's roads now, 2 billion by 2035: report, Green Car Reports, 2018.
  2. Road traffic injuries, World Health Organization, 2018.
  3. C. M. Philip, Deadly pits: potholes claimed 11,386 lives during 2013-16, The Times of India, 2018.
  4. S. Sherraden and S. Henry, Costs of the infrastructure deficit, New America, 2018.
  5. From plans to pavement: how a road is built, Michigan Department of Transportation, 2018.
  6. J. Careless, Turning the volume down, Asphalt Magazine, 2018.
  7. J. Lerner, The problems with potholes, 2018.
  8. U. Sohail, Goodbye potholes: the Netherlands is developing self-healing roads using steel fibres and bacteria, Wonderful Engineering, 2018.
  9. Eldredge, Barbara, The Netherlands is testing ‘self-healing’ roads that fix their own potholes, Curbed, 2018.
  10. A. García, E. Schlangen, M. van de Ven and D. van Vliet, Crack repair of asphalt concrete with induction energy, 2018.
  11. A. Chen, Have scientists discovered the cure for potholes?, The Verge, 2018.
  12. S. Campbell, MasterChef inspires engineer to cook up a new recipe for self-healing roads, The University of Nottingham, 2018.
  13. H. Lamb, Self-healing asphalt road method inspired by oily Masterchef technique, Eandt.theiet.org, 2018.

About the Author

Student, UCL

UCL Mechanical Engineering student who has always been passionate about how things work and how they are created. Always thinking about how to improve solutions to current problems to ease everyday life.

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