Concrete is the world’s most widely used building material. In an average year, the world uses nearly three tons of concrete for every man, woman and child—and concrete is only beat by water when it comes to materials used by humanity. That precious grey stuff is funneled into constructing bridges, buildings, and yes, sidewalks each year. Now, researchers in Korea are reporting that they’ve created an inexpensive and environmentally friendly coating for the inevitable cracks in concrete.
The problem with most concrete, say the researchers in the journal ACS Applied Materials & Interfaces, is that concrete often develops a spiderweb of tiny cracks—cracks that allow water, salt, and road salt speeds concrete’s deterioration. "Although several reports of self-healing anticorrosive coatings for metal protection have appeared, there have been no reports on self-healing protective coating for concrete," say the scientists.
They describe development of such a coating, one that contains microcapsules loaded with a material that seals cracks. Cracking ruptures the microcapsules, releasing the healing agent. Sunlight shining onto the concrete activates and solidifies the sealant. "Our self-healing coating … offers the advantages of catalyst-free, environment-friendly, inexpensive, practical healing," the report states.
This is not the first time researchers have sought to improve the world’s most common building material. Last year, researchers at Delft University were able to use bacteria to make a coating that patched over cracks in concrete. They embedded calcite-precipitating bacteria in the concrete paste mixture, and after a month found the spores of three particular bacteria where still viable. They are currently working on expanding and improving the project.
Another innovative project comes from a Nova Scotia startup called CarbonCure, which is looking to inject greenhouse gas-trapping carbon into concrete, sealing it up. Their logic? All concrete contains limestone, also known as calcium carbonate. This would just shove a little more carbon in the process earlier. They say it results in stronger concrete that is able to leave the factory sooner—a good outcome in all respects.