dumb as a rock

"Dumb as a rock"

Concrete is not a rock in a geologic sense so this doesn't pertain _sensu_stricto_.

"Rock is a naturally occurring aggregate of minerals and/or mineraloids" ^^^^^^^^

or any basic geology or high school natural sciences text.

When a geology student picks up a piece of weirdly weathered concrete and asks the prof what kind of rock it is with the hope of tripping her/him up, a good answer is " A piece of insubordination".

FWIW, the electrical properties of concrete have been recognized as important since at least the 1950's

....Marc Marc_F_Hult

Just how conductive is concrete? Can its conductance be improved? I'm thinking of UFER grounds where the rebars or mesh in concrete in contact with earth can be used as a ground electrode.

RF Dude

Here is to those that get their technical info "From an Article in The Christian Science Monitor...". The World Weekly News at the supermarket checkout line has some good info too! Ever see those photos of BatBoy?

And here's to those for whom "dumb as a rock" will forever be applicable.

Your friend Google

led quickly to:

a "scholarly" site cite that suggests it's all about slag:

Abstract Electrical conductivity measurements were made on concrete systems containing blast-furnace slag. It was found that the slag content significantly influenced the concrete conductivity. A linear relationship between the concrete conductivity and the slag content and the volume fraction of aggregate was established by experiment. The relationship can be expressed as follows sc = ka·fa + ks·(?slg&den;c) + kowhere sc is the concrete conductivity; fa is the volumetric fraction of aggregate; (slg/c) is the relative content of slag by weight of cementitious materials; and ka, ks, and ko are empirical coefficients. This relationship provides a basis for the determination of slag content in hardened concrete by electrical conductivity methods.

Keywords: blast-furnace slag, concrete, electrical conductivity, portland cement

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I like the word cementitious. Might be a good synonym for block head or the phrase, dumb as a rock.

Now if you're into "interfacial zone thickness" then you might want to look at:

It's pretty scholarly, too. :-)

Is the Virtual Cement and Concrete Testing Laboratory of the National Institute for Standards and Technology, Building and Fire Research Laboratory.

-- Bobby G.

I suppose it depends on the composition.

Dr. Chung is adding carbon fibers, turning it into a large strain guage the resistance of which increases with stress.

LOL

This technology has been developing for _at least_ a dozen years. Apparently Dave and CSM jist picked it up for whatever reason,

Pu-Woei Chen and D D L Chung Dept. of Mech. & Aerosp. Eng., State Univ. of New York, Buffalo, NY, USA Print publication: Issue 1 (March 1993)

Abstract. Electrically conducting concrete, as provided by the addition of a short carbon fibers (0.2-0.4 vol.%) to concrete, can function as smart structure material that allows non-destructive electrical probing for the monitoring of flaws.

Lisa Randall had an interesting op ed in Sunday's NYT that deals, among other things, with piecemeal extraction and popularization of the latest scientific "breakthrough" -- well worth the read. Reprinted here:

Marc Marc_F_Hult