Conductive Concrete Offers Building Security

zdburke writes: "In a slightly different spin on the electromagnet-protected server room in Stephenson's Cryptonomicon, the folks at the National Research Council have developed concrete that conducts electricity, or 'percolates,' allowing it to serve as an electromagnetic shield. Current uses lean toward heated loading docks, non-freezing bridges, and grounding large-scale electrical equipment, but the counter-espionage idea is cool. The NYTimes has a brief story, and the folks at UN Omaha have some great pictures. It's not exactly new (it won a Popular Science prize in 1997) but it's still cool stuff."

Comments

Blocks Cell Phones?

[hoggoth]

I wonder what kind of cell phone signal I would get in a conductive-concrete building? Probably next to none...

Cost and Uses

[Digitalia]

Is the cost per cubic foot much greater than standard concrete? If not, then I'd be interested in the implications for using it as a residential flooring substrate. Rather than going for a standard radiant heating system, would it be more efficient to employ this?

Non-freezing bridges?

[PhysicsGenius]

Sounds like these guys have never studied thermodynamics. It takes 333kJ to melt a single kilogram of ice. To melt it in, say, 10 minutes (= 600 seconds) would require 555 watts. Not so bad? Consider the following: Conservatively estimate a bridge to be 10 meters wide by 250 meters long and having 2 centimeters of ice. That's 50 m^3 = 50,000 kg of ice. A mere 28 MegaWatts. Per ice storm. Per bridge. Assuming 100% efficiency. Oh yeah, no problem.

Please study a little science before you post stories from similarly unclued "visionaries".

Re:Non-freezing bridges?

[tkrabec]

But if you can keep the ice from forming the water could run off the bridge and not freeze.

-- Tim