Helping Concrete Heal Itself

Concrete is one of civilization’s most durable building materials. The ancient Romans used concrete 2,000 years ago to make structures that still stand today. People now use the material’s modern versionaggregates such as sand or gravel held together by a cement and water pastemore than all other construction materials combined. The world produced 4.3 billion metric tons of cement in 2014, and this production will keep increasing as more sidewalks, buildings, and bridges get built in an increasingly urban world. For all its strength and durability, though, concrete has problems. Stress from carrying loads gradually creates microscopic fissures in the material that allow in water, salts, and ice. These fissures can then turn into gaping cracks, exposing the steel bars often used to reinforce concrete to corrosive elements. Our seemingly resilient infrastructure would crumble without routine, and costly, patching. To help reduce those maintenance costs and make buildings and bridges safer, researchers are now giving concrete the power to heal itself. By extending the lifetime of structures, self-healing concrete could also reduce the use of concrete for rebuilding and cut concrete’s impact on the environment. Cement production creates roughly 9.5% of global carbon emissions, according to a recent European Commission report. And concrete use is set to skyrocket, due to a building boom in countries like China, which used more cement from 2011 to 2013 than the U.S. used in the entire 20th century, as detailed in the Washington Post.