Concrete is great stuff, but when it gets damaged — forming potholes and cracks — it can be annoying and dangerous. It can also be hell on your car’s suspension, tires, and gas mileage.
Road damage usually happens over time, and can often be blamed on something called “microcracking.” Over time, tiny cracks form in concrete that allow water and pollutants to seep in and corrode it. What starts off as a small, barely visible problem can eventually deteriorate into a severe safety hazard.
The total costs of fixing roads in the United States is around $166 billion a year, and the American Association of State Transportation and Highway officials published a report in 2009 which estimated that damaged roads can cost a driver between $335 and $746 per year in reduced fuel efficiency and repairs.
But Korean chemist Chanmoon Chung, a chemist at Yonsei University, was part of a team that has invented a sprayable protective coating that can heal cracks in concrete as they form. It could save billions of dollars a year in the U.S. alone.
How it works is simple. The liquid contains countless tiny microcapsules filled with a healing solution. When there is damage to the road — say, by car or truck tires — the capsules burst and fill the tiny cracks the tires create so they don’t propagate.
There are some similar self-healing concretes and protective coatings already, but they need chemical catalysts to activate the healing solution. Chung’s solution can harden using just sunlight.
We asked him about the new product:
Business Insider: So what are microcracks and why are they a problem?
Chanmoon Chung: When cracks form and propagate in concrete, water, chloride ions, and carbon dioxide penetrate through the cracks. This results in the deterioration of concrete, leading to a reduction in its serviceability.
BI: Can you tell me how your solution is different from the others currently available?
CC: A typical extrinsic self-healing system employs a microencapsulated healing agent and a (microencapsulated) catalyst. When microcracks propagate through the matrix, the healing agent is released from ruptured microcapsules and polymerizes on contact with the catalyst to repair the damaged region.
However, there are limitations of this system, including catalyst availability, cost, environmental toxicity, stability, and materials processing. Recently catalyst-free, self-healing systems have been studied to develop less expensive and more practical ways to self-repair polymeric materials. One autonomous, catalyst-free approach is self-healing under natural conditions, for example, in the presence of sunlight.
BI: About how long does it take to heal, once the capsules have been ruptured?CC: In this paper self-healing was achieved by exposure to sunlight with relatively low intensity for 4 hours (the experiment was performed in November).
BI: Some of the news reports have said this polymer could save governments a lot of money in road repair. What are some of the other applications on which this coating could be used?
CC: Basically our self-healing coating system can be used anywhere concrete structures are present. We think that our system is especially suitable for concrete structures that are difficult [to] access (for example, a bridge over the sea). It can be difficult to inspect such concrete structures, so microcracks may cause big safety problems without recognition.
BI: What about something like an outdoor concrete water tank or a pool? Could the polymer work if it were at the bottom of a swimming pool filled with water?
CC: We think the coating might work to some extent in the water. In the case that the coating can’t be exposed to sunlight in the water, just recoating by the healing agent in the crack region may occur.
BI: Could this work in places that have little sun during certain times of the year, like Alaska or Iceland?
CC: I think that the self healing coating could work under the conditions of little sun and intense cold because the healing agent has relatively high flowability and photoreactivity even under low temperatures.
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