Scientists ape Zeus, experiment with lightning to recycle concrete

Don't worry, scientists are using their powers for good when they harness lightning in a lab to destroy concrete. The lightning zap breaks up the rubble into its core components without all the environmental mess created by shredding it.

With that kind of power, let's remember to not make scientists mad. Plus, using the lightning method the core components can be used again so a building could rise from the waste of another.

So what's the big problem with concrete? Why zap it — and, for that matter, how is hitting concrete with lightning better than just crushing it? Well, concrete is a bit of an environmental nightmare all around. Creating it contributes to CO2 production and the ability to "recycle" it is limited. Inherently its pretty hardy stuff and when it is shredded it creates unhealthy dust and just smaller bits of the same rubble.

Given the millions of tons of concrete waste being created around the world whenever we want a new road or to tear down an old building, scientists at the Fraunhofter Institute's Concrete Technology Group in Holzkirchen, Germany wanted to create a way to truly recycle the concrete instead of just down-cycling it into dubiously useful rubble.

The answer came through a 70-year old discovery from Russian scientists. They learned a process called electrodynamic fragmentation breaks things down to their original components. Their experiments discovered the principle of dielectric strength. This means the resistance of fluids or solids to electrical impulses is not a physical constant, but actually changes based on the duration of the lightning or electrical impulse.

We all know that lighting likes to travel through water rather than a solid — it's why we all jump out of the pool when there is a storm. Well, when scientists tinker with the duration of the electrical impulse that travels through the water it turns out to be even scarier than we think.

Using the principle of dielectric strength, the Fraunhofer researchers discovered that a 150-nanosecond bolt of lightning traveling through water can actually enter concrete. When hit with that short, intense bolt of lightning, it will pass through the water into the concrete using the paths of least resistance — which would be through the bonds between the components of the concrete which are cement, aggregate rock and water.

Volker Thorne from the Fraunhofer Institute describes the process vividly in a press statement:

"At this instant a plasma channel is formed in the concrete which grows within a thousandth of a second, like a pressure wave from the inside outwards. The force of this pressure wave is comparable with a small explosion."

Aside from the playing with lightning part (and conjuring images Death Star-style demolition), why should we care about exploding concrete?

This process takes the concrete down to its raw components again, not just messy rubble. Having the raw components be reborn out of the explosion allows engineers to make brand new concrete. Though it sounds like Frankenstein, it's a good thing. It creates a useful recycling loop.

Currently, the researchers can process one ton of concrete waste per hour in their laboratory fragmentation plant. According to the company, the next step is to increase the rate of processing and look for a way to create a cement substitute from the waste. The combined efforts could make the industry cleaner and ultimately cut costs throughout the industry.

Fraunhofer Institute, via Gizmag

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