Materials

Dash of nanocarbon black makes conductive, heat-generating concrete

Dash of nanocarbon black makes...
Running a current through the conductive concrete warms it up
Running a current through the conductive concrete warms it up
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Small samples of MIT's new conductive concrete
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Small samples of MIT's new conductive concrete
Running a current through the conductive concrete warms it up
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Running a current through the conductive concrete warms it up
The new conductive concrete is made by mixing in small amounts of nanocarbon black
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The new conductive concrete is made by mixing in small amounts of nanocarbon black
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Concrete is pretty useful, which is why it’s the most widely used construction material in the world. But it could be argued that it doesn’t really do anything. Now, engineers have made concrete that can conduct electricity and produce heat, by mixing in nanocarbon black.

Normally, concrete is an insulator against electricity, but recent research has focused on making it conductive. Adding some form of carbon to the mix usually does the trick, with past versions being tested in airport runways that automatically melt snow.

For the new study, researchers at MIT’s Concrete Sustainability Hub (CSHub) and the French National Center for Scientific Research (CNRS) added nanocarbon black, which is a cheap carbon material that boasts excellent conductivity, to concrete. At just a four-percent volume, the concrete was able to carry an electrical current – and as a result, it gave off heat too.

“Joule heating (or resistive heating) is caused by interactions between the moving electrons and atoms in the conductor,” says Nicolas Chanut, co-author of the study. “The accelerated electrons in the electric field exchange kinetic energy each time they collide with an atom, inducing vibration of the atoms in the lattice, which manifests as heat and a rise of temperature in the material.”

The new conductive concrete is made by mixing in small amounts of nanocarbon black
The new conductive concrete is made by mixing in small amounts of nanocarbon black

In tests, the team found that the nanocarbon black concrete was extremely effective at producing this heat. A voltage as small as five volts was enough to boost the surface temperature of the concrete samples to about 41 °C (106 °F). This could not only find use for de-icing surfaces outdoors, as other conductive concretes have, but the team says the material could make its way indoors too.

“This technology could be ideal for radiant indoor floor heating,” says Chanut. “Usually, indoor radiant heating is done by circulating heated water in pipes that run below the floor. But this system can be challenging to construct and maintain. When the cement itself becomes a heating element, however, the heating system becomes simpler to install and more reliable. Additionally, the cement offers more homogenous heat distribution due to the very good dispersion of the nanoparticles in the material.”

The research was published in the journal Physical Review Materials.

Source: MIT

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4 comments
paul314
Can the carbon black be added to only part of the mix? Otherwise you're going to need to insulate from the ground in a serious way.
Username
The larger the piece the more resistance it will have so 4 volts is nowhere near what will be required for a runway. Also, at what amperage?
Expanded Viewpoint
Unless it's out in an arid desert, concrete absorbs water and conducts electricity very well. A neighbor who used to live up the street from us had a small dog who was kept outside at night. In the winter time, he would want to come in the house to be warm, so he would tap on the metal screen door with his paw. Bill hooked up the screen door to the hot side of an old lamp cord, and when the dog touched it while standing on the concrete patio, he got a good jolt of 110 Volts! It took him only a couple of shocks, and he never banged that door again!
mikewax
not the larger, the LONGER the slab the more resistance it has. And the wider and deeper, the less it has.
R = length / cross-sectional area.
it might work better than gas in some cases, like a bathroom or a sauna.