Could plastic replace steel in bridges?

University of Houston researchers testing carbon reinforced polymer beams

HOUSTON - As the country's highways, byways and particularly bridges get older the steel reinforcement inside the concrete corrodes and weakens.

A University of Houston professor believes plastic could be the remedy engineers need to fix the country's aging infrastructure.

"Corrosion is a problem, and this material has proven to be very good material for such situations," said Dr. Abdeldjelil, "DJ," Belarbi.

Dr. Belarbi and a team of students, faculty and post-doctoral researchers are conducting testing on carbon fiber reinforced polymers, CFRP,  inside concrete bridge girders.

Girders are the beams that actually support the deck and traffic in a bridge, and corrosion in steel girders has become a problem across the nation.

Dr. Belarbi calls it the cancer of bridges.

The Federal Highway Administration considers bridges that need to be watched and potentially repaired structurally deficient.  According to their database for 2013, there are 260 in the Houston metropolitan area with this distinction.

The American Society for Civil Engineers reports that 1 in 9 bridges across the United States are rated as structurally deficient. 

Inside the HU structural engineering lab, pieces of the CFRP lay side by side next to heavy steel rebar.

The material is much lighter than steel but Dr. Belarbi says it's four to five times stronger and it is corrosion-free.

To test it's strength and characteristics his team is loading large girders into a machine that can mimic the weight of 2 to 3 fully loaded 18-wheelers.

They apply pressure onto the beam until it breaks in order to determine proper load limits and develop code specs for engineers.

"For engineers to be able to design anything they have to have some code and guidelines available to them," he said. "If they don't have it, they would be nervous and not comfortable to use this material. Our job at the University of Houston is to try to enable engineers to be able to use those materials in the future."

According to Dr. Belarbi, engineers have already begun to use CFRP in other components of bridges but using it as pretensioning has never been used in a main support girder.

In the first round of testing, the CFRP beam proved to perform just as good as a steel prestressed beam.

There are 12 more rounds of testing before the results are published sometime next year.

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