When you hear the word 'nanotechnology,' I bet you immediately think about nanochips or ultra-small medical devices. But do you know that nanotechnology is starting to be used in highways, bridges and other buildings? In "Small Science Will Bring Big Changes To Roads," a very long article from Better Roads Magazine, you'll discover that "research in structural polymers could lead the way to guardrails that heal themselves, or concrete or asphalt that heal their own cracking." Nanotechnology is also used to design better steel or concrete. And there are even nanosensors in place on the Golden Gate Bridge to monitor its behavior. The nanotechnology revolution is on its way, even if self-healing potholes and guardrails are still science fiction.
This long article discusses nanotechnology advances in concrete and cement, self-cleaning traffic signs, better steel or embedded nanosensors.
As a taste of what might come, in April 2003, Turner-Fairbank workshop participants discussed the potential for embedding nanosensors in road pavement to monitor processes that contribute to deterioration and cracking. The data would be accumulated in a database for researchers to use for extending the service lives of pavements. Similar sensors on bridges might monitor vibrations and loads, enabling researchers to assess structural weaknesses and conditions and fix them long before they are even apparent to human inspectors.
Another application envisioned by the workshop participants would be to improve the collection of traffic data used by transportation managers. Networks of nanosensors embedded in roadways could provide real-time information to better manage congestion and incidents, or to detect and warn drivers about fast-changing environmental conditions, such as fog and ice.
Also, the University of California-Berkeley is experimenting with MEMS they call Motes. The Golden Gate Bridge now has an experimental sensor network of approximately 200 small Motes, each with an accelerometer that measures movement such as traffic, wind, or seismic loads. When all sensor readings are correlated, a three-dimensional picture is created which may portray structural abnormalities.
And here are selected excerpts about self-healing pavements.
The idea of pavements or guard rails healing themselves after being damaged truly is the stuff of science fiction.
Work on self-healing polymers already is under way at the University of Illinois Urbana-Champaign, by Professor Nancy Sottos and her Sottos Research Group, which has developed a structural polymeric material with the ability to autonomically heal cracks.
Autonomic (spontaneous) healing is accomplished in this program by incorporating a microencapsulated healing agent and a catalytic chemical trigger within an epoxy matrix. An approaching crack ruptures embedded microcapsules, releasing healing agent into the crack plane through capillary action. Polymerization of the healing agent is triggered by contact with the embedded catalyst, bonding the crack faces.
A similar process has been described in which microsized hollow fibers filled with crack sealant would be introduced into concrete. If the concrete cracked, the fibers would also break and release sealant. This would be especially applicable for bridge piers and columns suffering from microcracking and requiring costly epoxy injection.
This panorama of nanotechnology advances in construction would not be exhaustive without speaking of 'smart dust,' or nanosensors the size of the dot at the end of this sentence.
Department of Defense (DOD) Smart Dust would be distributed by air over a war zone to give planners a three- or four-dimensional visualization. They could easily go behind enemy lines, or be situated in the lairs of the enemy, providing real-time reconnaissance. Smart Dust gone awry and deadly was the nemesis in Michael Crichton’s 2002 bestselling book, Prey, now in movie production at Fox.
In the future, though, Smart Dust may have application for transportation infrastructure.
"An entire computer and strain measurement sensor system could be placed on a silicon chip, and made very small," said Dr. Richard A. Livingston, senior physical scientist, at the FHWA’s Advanced Infrastructure Research program, to Better Roads. Smart Dust incorporating minute transponders, which don’t emit radio waves until stimulated by an external signal, would eliminate the need for a bulky battery. "These fine particles could be distributed over an entire bridge structure to monitor the entire structure at once," Livingston said.
If the Better Roads article is not enough to satisfy your curiosity, please visit the Turner-Fairbank Highway Research Center (TFHRC), one site of the Federal Highway Administration (FHWA). Check for example the Materials Technology Research page.
Sources: Better Roads Magazine, July 2004; Federal Highway Administration (FHWA)
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