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.

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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.

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