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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."
Anyone remember the name of that psychologist that put dogs in a room with an electrified floor? I wonder if they'll start putting this stuff into jail cells and mental hospitals. You know, the prisoner/patient/subject mouths off they can give them a jolt. All in the name of science, of course.
I wonder what kind of cell phone signal I would get in a conductive-concrete building? Probably next to none...
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I'm not a huge expert in the realm of physics (dammit, Jim, I'm a computer scientist!), but is this anything like a massive Faraday cage, which would prevent electromagnetic waves for entering and exiting?
:-)
I shudder to think of the day when we will work in protective buildings like these, keeping company secdrets safe from Van Eck phreakers and war drivers, but also keeping out the mellow, smooth sounds of Office Light Jazz 94.7.
Karma: Excellent Birds (mostly as a result of listening to Laurie Anderson)
Anyone remember the name of that psychologist that put dogs in a room with an electrified floor?
Pavlov. That was one of several experiments involving behaviour modification.
Eve Fairbanks says I drive a hybrid!LOL
So this stuff can conduct electricity, meaning it could generate a magnetic field, right? So you could theoretically generate a magnetic field to hold a concrete structure made from this stuff in the air. Does this mean that my goal of making a floating castle like all the bad guys in RPG video games have is finally within reach?
That unomaha site has one of the worst web designs I'ver ever seen. I guess it's not that important that scientist be designers, but readability would be a good thing to strive for. I don't need every paragraph to be a different color. Is this a side effect of too much exposure to conductive concrete?
Starsucks
I remember when a friend was recording a radio theatre show, the studio had chicken wire on all the walls (behind accoustic foam in most places) to minimize inteferrence from outside signals. You don't want your microphone cable picking up radio signals when recording a performance. This material could be ideal for construction in applications like that where you want to block out outside signals.
How about drywall transistors and logic-gate carpets?
I wont be happy till my split-level serves pr0n.
(2,3-Benzopyrrole)
The most obvious use is heating.
But wouldn't it be cheaper and simpler to embed, say, a PVC 2-inch pipe in the concrete, and run warm water through that? Note that you can use this method with just about anything (dirt, asphalt, etc) and keep it from freezing.
If you want a method to directly heat it using electricity, run stainless steel pipe instead, and use it as a load.
I've frequently wondered why civil engineers haven't implemented either of the above techniques before. Chalked it up to "roads don't freeze enough".
Thoughts?
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First day here, huh?
This next song is very sad. Please clap along. -- Robin Zander
But if you can keep the ice from forming the water could run off the bridge and not freeze.
-- Tim
TKrabec Pahh
It sounds like the concrete still has a pretty high resistance, so I wouldn't count on a reasonable thickness forming a good Faraday cage. With the conductive stuff costing At 2 or 3 times as much, you could likely get a better cage for less by just hanging metal mesh inside the forms and pouring regular concrete. (The mesh is part of your reinforcement, too.)
And the suggested use of electrically heated payment leaves me wondering where they plan to get free electricity.
But there is one good application for this. Electronics manufacturers need to control static throughout their facilities. Fixed objects are grounded by hooking up wires, but people walk around, circuit boards and parts are carried around on carts, etc., and the only way to ground these while in motion is through the floor. So we paid plenty for conductive tile, and some sort of conductive underlay. If we could have put a conductive layer in the concrete slab itself, it would have saved a bunch (even at 3x the price of regular concrete), and it would be more reliable and lower maintenance.
Something I discovered with a neon transformer is that most things are conductive to some degree if you apply enough voltage :) concrete included.
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Harder.
I am a field engineer on a bridge construction project. I do concrete and overlays.
In most areas of bridges near water epoxy coated or galvanized rebar is used instead of black (bare) steel. The problem is that when steel rusts, it expands, popping the concrete around it.
When you build reinforced concrete the term 'cover' refers to the minimum distance the rebar must be from the outside faces of the concrete - basically the distance between the steel and the corrosion. This 'cover' is typically between 2 - 5 inches.
Overlay concrete (of which this conductive concrete is a type) is the riding course, or the top layer you actually ride on. It is poured seperately due in part to the large effort required to get the nice arched surface that rides so well. Overlays are typically 1 1/2 to 3 inches thick.
So, a "thin" layer, thiner than the typical cover, with metal particles spread uniformely enough to conduct electricity is bound to corrode like a bastard.
There are ways that you could combat this, though. Galvanize the parts, imbed a wire mesh that is plastic coated and electrficy that, apply one hell of a sealant, or put an ungodly amount of DCI (corrosion inhibiter) in the mix. DCI has a number of side effects that make it hard to place, displaces a fair amount of water, and it is really hard to finish smoothly.
I think I need a new sig here.