N.Y. -- The failure of levees in the wake of Hurricane
Katrina points out the need for new technologies
to strengthen levees and monitor their reliability,
according to Deborah D. L. Chung, Ph.D., a University at Buffalo materials scientist
and inventor of "smart concrete."
"The technology used to build levees is really very
primitive -- sometimes it involves just the piling
of dirt. Surely there's a lot of room to use higher
technologies than that," says Chung, Niagara Mohawk
Professor of Materials Research and director of the
Composite Materials Research Laboratory in the UB
School of Engineering and Applied Sciences.
Chung's smart concrete, patented in 1998, may be
one such technology whose time has come for commercial
use -- not only in the construction of levees, but
for a range of disaster and homeland security applications.
With smart concrete, short carbon fibers are added
to the conventional concrete mixture. This modification
gives the concrete the ability to detect stress and
tiny deformations in the concrete. In the presence
of structural flaws -- within a levee made of smart
concrete, for example -- the concrete's electrical
resistance increases. This change can be detected
by electrical probes placed on the outside of structures.
"You could use a meter to continuously monitor stress
and deformation within levees made of smart concrete," Chung
explains. "When deformations in the levee deviate
from an acceptable baseline, an alarm could be triggered."
Similarly, the electrical properties of smart concrete
could be used to detect underground stress that builds
prior to an earthquake, to monitor building occupancy
for intruders or for stragglers during an evacuation,
and to monitor traffic flow in an emergency or around
U.S. borders, Chung says.
Chung, who also has studied the use of continuous
carbon fibers in the form of composites, suggests
that some levees could be encased in a shell composed
of such composites, which are similar to the material
used to form the bodies of jet aircraft.
"If you use that as the outer shell of a levee,
you could make use of the carbon fiber's electrical
conductivity to monitor fiber breakage," she says. "So
in addition to serving as levee reinforcement, the
shell also serves as a sensor of damage."
According to Chung, use of smart concrete would
increase construction costs by 30 percent, which
is a main reason industry has not adopted its use,
she says. Of course, reconstruction costs after a
disaster can run much higher, she points out.
"People might say they like sensing, but in real
life do they really want their bridge or their highway
to be smart," Chung asks. "When it comes to real
construction projects, all they really care about
is mechanical behavior, and every penny counts in
the bidding process."
The University at Buffalo is a premier research-intensive
public university, the largest and most comprehensive
campus in the State University of New York.
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