At first blush, the scenario seems surreal, counter-intuitive and impossible. A 70-ton US Army M1 Abrams Main Battle Tank crossing a bridge constructed entirely of composite plastic looks both sheep folly and a recipe for disaster.
The reality is, unquely though it seems, the world's first such bridge exists at Fort Bragg, NC and the M1 first rolled over it during demonstration last summer. The bridge built of material developed by Axion International of New Providence, NJ flexed as designed and returned to its original position after the tank crossed. The long-term implications and applications of such technology seem boundless.
Proprietary technology developed in consort with scientists from Rutgers University is applied to non-biodegradable items such as milk jugs, electronics housing and shampoo bottles that typically wind up choking landfills. The process involves blending the plastics, melting them in an extruder and molding functional building shapes. The result is an inert, thermoplastic material that is structurally stronger than other non-structural plastic lumber.
"By taking plastic that would otherwise wind up in landfills and recycling it into next generation generation materials, Axion is helping to save the environment while creating infrastructure products for bridges that are strong enough to drive a tank over," proclaims Axion CEO James Kerstein on the corporate website.
The product resists rot and corrosion, resulting in significant maintenance savings, and is both 100 percent recycled and 100 percent infrastructure-ready. Although not yet code listed by the International Code Council (ICC), the thermoplastics have undergone testing by the American Society for Testing and Materials (ASTM) and can replace wood, steel and concrete in bridge structures. Fort Bragg's bridge has a 73-ton rating for tracked vehicles, like tanks, and an 88-ton rating for wheeled vehicles.
The product is lab and field tested by the US Army Corps of Engineers, military procurement departments, Rutgers, the University of Illinois and the American Association of Railroading Test Track. Axion's technology has already been rejected in the installation of more than 200,000 railroad crossties across the United States and can also be used for marine pilings.
ENGINEERED CEMENTITIOUS COMPOSITE
Development of Engineered Cementitious Composite (ECC) – bendable concrete with self-healing properties – has come in response to concrete's brittleness, lack of durability and failure under strain. Initially used to enhance the safety of buildings in active seismic zones, ECC has applications across the design spectrum.
At the forefront of research is Dr. Victor C. Li, the E. Benjamin Wylie Collegiate Professor of Civil and Environmental Engineering and professor of Materials Science and Engineering at the University of Michigan, who work dates back to 1990. He delivered keynote addresses on ECC at conferences in South Africa last November and Chicago last June.
"Because ECC maintains all the advantageous properties of normal concrete, but also incorporates metal-like ductility and self-healing functionality, the range of applications can be greatly expanded too much beyond what concrete has traditionally been used for," says Dr. Li, also a senior partner in a small consulting company (LFL & Associates) working to bring the technology to market. "The technology is ripe for a variety of commercial applications and some government agencies can help accelerate the process."
Under the watchful eye of the Michigan Department of Transportation, ECC was tested on a patch repair of a bridge deck in Ann Arbor in 2002 and a link-slab for a bridge deck in Ypsilanti in 2005. A 60-story residential tower completed in Osaka , Japan in 2008 used ECC in the coupling beams through the building's core.
OTHER PRODUCTS OF NOTE
Paint based on the human skin's healing abilities is being developed by researchers from the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, Germany together with collections from Duisburg-EssenUniversity. Researchers there are working to perfect electroplated layers with embedded nano-capsules filled with liquid that ruptures when a scratch occurs to spill treating agents into the damaged area.
Celanese Emulsion Polymers rolled out low VOC (Volatile Organic Compounds), eco-friendly, waterborne interior paints at Paint India held in Mumbai in early March. The water-based paint retains high-performance characteristics such as superior wet scrub resistance.
As green building moves from trend to mainstream, designers and contractors continue to develop innovative ways to do more with the materials at hand. Rather than being burned, rubber tires are now recycled and used in a variety of ways ranging from backyard mulch to kitchen floor tiles. Demolition waste is regularly re-purposed and re-used on construction sites.
It's a brave new world and, as OMNIBUILD LLC founder John Mingione told Construction Digital Nearly two years ago: "It's simple – if you're not in it now, then you're going to get lost in this business. "