Sometimes good ideas hit you like, well, a bolt of lightning. For decades, concrete recycling has been a laborious and inefficient venture. Millions of tons of construction waste, much of it concrete, are generated each year in the United States. Every time a new road is paved, a new building is built, or a bridge is erected, there is waste. Some of it’s the old concrete that was torn up, some of it was leftover from the new structure.
Manufacturing concrete is a dirty business, contributing to an estimated 8 to 15 percent of global CO2 production. Recycling concrete instead of dumping in a landfill would be ideal, but the current shredding method produces a huge amount of dust and an inferior product. Using a 70 year-old study as their guide, researchers from the Concrete Technology Group in Holzkirchen, Germany, recently discovered that if they can convince a bolt of lightning to strike a pile of concrete rubble, it accomplishes in minutes what would otherwise take hours or days.
Now, in case you’re wondering, the lightning used by the researchers to develop this method of concrete recycling doesn’t come from the sky. Waiting for a random bolt to do your bidding would be the opposite of efficient. Instead, the German researchers used laboratory-generated lightning to test their theory.
They found that, although lightning normally prefers traveling through air or water, very fast strikes will often travel through a solid. When passed through a pile of concrete, “lightning travels along the path of least resistance: the barriers between the gravel and cement stone. This tears the concrete apart, separating it into its fundamental components – ripe for maximum recycling,” writes Gizmag’s Will Shanklin.
This method has already allowed the researchers to process concrete at a rate of one ton per hour. “To work efficiently, our goal is a throughput rate of at least 20 tons per hour,” says Volker Thome from the Fraunhofer Institute for Building Physics. In as little as two years’ time, a lightning-based concrete recycling system could be ready for market-launch.