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Concrete:
A Public Radio Commentary
by Bill Hammack
Listen using RealAudio
Recently while waiting for an appointment, I starred out the
window and watched an ancient art: The making of concrete.
The origin of the word gives away its ancientness. It's made by
combining the Latin prefix com meaning "together," and crescere
meaning "to grow." The names comes about because when the
ingredients making up concrete - water, gravel, sand, and a bit
of cement - are mixed they turn into a hard, rigid solid.
The Romans discovered concrete by accident. A builder was making
some mortar and he happened to be working near Mount Vesuvius,
the famous volcano. He tossed in some volcanic ash and noticed
that when his mixture dried it made a very hard substance.
From this serendipitous beginning the Romans fine tuned the
recipe for concrete. They mixed horse hair to reduce the amount
it shrank during hardening; and they also added blood, which made
the stuff frost-resistant. Today we use plastics for horse hair
and special chemicals instead of blood, but the same principles
apply.
With these innovations Roman concrete reached a level of quality
unmatched until this century. Just look at the Pantheon, the
Temple of the Gods.
The Roman Emperor and builder Hadrian capped its rotunda with a
144 foot in diameter concrete dome. Michelangelo found it so
beautiful he called it "angelic" and declared it "not of human
design."
Although the Pantheon is the most visible example of Roman
concrete engineering,
our age the concrete industry is so important that it now takes
up about 10 percent of our gross national product. And it
promises to take up even more.
Perhaps the most bizarre application for concrete is in making
ships and submarines. Although not well known concrete will float
if you add enough air to it. A concrete submarine can dive deeper
than a metal one because concrete is very strong under pressure.
Once submerged it would be hard to detect. A concrete submarine
fools sonar into thinking its the ocean floor.
Now, concrete is becoming high tech. Engineers are inventing
smart concrete that can conduct electrical signals. It'll be able
to detect vehicles, perhaps even guide one down a highway. And
when used in buildings it might even detect earthquakes. Although
I note that the Romans needed no such thing: After 2000 years the
concrete dome of the Pantheon is still standing.
Copyright 2001 William S. Hammack Enterprises
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