Concrete, a hard and porous composite of cement, sand, aggregate and gravel, forms the foundation of most bridges. It holds up well to compressive forces (those that push down at right angles), but not as well to tensile forces (those that act along the length of the material to pull it apart). Engineers use steel bars, also known as rebar, to reinforce the tensile strength of concrete.
Unfortunately, steel rebar can corrode when exposed to freshwater or saltwater, which can cause distress in the concrete. One method to prevent this wear and tear involves coating the rebar with epoxy to shield the steel from corrosive chemicals. But scientists at the University of Wisconsin-Madison have developed another solution -- a reinforcing matrix made from a novel fiber-reinforced polymer. Because it is nonmetallic, the polymer material won't corrode, which means the concrete remains stronger longer.
The first real-world test of this new and improved concrete is the DeNeveu Creek Bridge, a 40-meter (131-foot) span along Highway 151 in Fond du Lac, Wis. Driving over the bridge, you would never know there is anything special hidden inside the nondescript box girder bridge. But the real payoff will come far into the future. The bridge deck is durable enough to last at least 75 years, whereas most traditional bridge decks last between 30 and 40 years before they need to be replaced. That means the DeNeveu Creek Bridge, completed in 2005, may not need any significant maintenance until 2080!