The material, developed by the French materials firm LaFarge, contains fine particles of sand, cement and steel fibers in a matrix that is denser and stronger than standard concrete.
"The fail rate of any one element is gradual, as opposed to more brittle material, and that gives you more time to respond," said Phares.
What's more, a beam made from the ultra-high-performance concrete can hold twice the load of beam made from the standard stuff. The scientists used the concrete to build a bridge over Little Soap Creek in southeast Iowa's Wapello County and are currently designing a second one that will go into Buchanan County.
Sensors and Sensibility
Federal law mandates that any bridge spanning more than 20 feet be inspected once every two years. But what happens in the meantime? How extreme heat and cold, traffic accidents, earthquakes, tornadoes, hurricanes and chemicals such as road salt compromise the structure's integrity is often unknown and unmonitored.
"We need faster technologies that allow us to look at a broader scope of the bridge," said Kenneth White, professor and head of the civil engineering department at New Mexico State University.
To address this, White and his team have turned three Department of Transportation bridges in Las Cruces into "smart bridges" by embedding fiber optic sensors into each.
Acting as an architectural nervous system, the fiber optics continually screen the structure for signs of damage or deterioration by shooting out beams of light along the network.
Sensors located along each optical fiber pick up the reflected light and send it to a computer housed in a control box nearby. A program analyzes the signal for abnormalities.
"If some damage occurred to the structure, that abnormality would be picked up by these sensors. If the stress got too high, it would send off an alarm," said White.
For now, the technique is hard-wired with cables running from the fiber optics to the control box. But a wireless version is possible, said White. That would allow engineers working in a central office to receive data from remote locations and could also improve recovery of data should the bridge become damaged and otherwise snap communication lines.
Inspector Robot
Until embedded sensors become a reality, inspectors must still go through the time-consuming, labor-intensive, and sometimes dangerous work of examining bridges.
Current rigging and traffic control measures consume 40 to 50 percent of costs associated with the inspection. Typically, traffic must be shut down, while the inspector, perched in a basket crane underneath the bridge, accomplishes the task.
Howie Choset, associate professor of robotics at Carnegie Mellon University in Pittsburgh, and his team are working on a robot that could cut those costs at least in half.
