Henry Grabar is a staff writer for Slate’s Moneybox and a former fellow at CityLab. He lives in New York.
Who says recycling can't be fun?
Since I praised concrete for its beauty and versatility last month, it seems only fair that I deliver the bad news as well. Concrete has a rather poor environmental record: eight to 15 percent of global CO2 emissions can be attributed to concrete production, and when concrete buildings are destroyed, the material is virtually unrecyclable.
Currently, the composite can be what researcher Volker Thome calls "downcycled", meaning crushed into a dusty pile of rubble used as a base for roads or other junk applications. But in this press release from the Fraunhofer Institute (the same German engineering behemoth that invented the world's longest bus), Thome explains that researchers have come up with a way to effectively break down the components.
The method? Blast chunks of concrete with enormous bolts of electricity. You'd think that if lightening made concrete split into its component materials, it wouldn't be the best building material. It turns out there's a trick.
The Fraunhofer researchers worked off a 70-year-old discovery by Russian scientists that dielectric strength (the resistance of a material to electricity) depends on the duration of the shock. Long shocks like lightning bolts travel through water rather than solids, and metal rather than brick. But during very short blasts of electricity, the dielectric strength of water is very high. Higher, in fact, than the bonds of concrete.
Thus, by rapidly shocking a pile of concrete in water, researchers can cause the composite to disintegrate into component parts in a series of small explosions. Currently, Thome and the Concrete Technology Group are able to go through one ton of concrete per hour; they want to do 20. The technology could hit the market as soon as two years from now.
Top image: Fraunhofer Institute.