Explosive failure expected when engineers take innovative bridge beam to its limits

AMES, Iowa -- Four hydraulic devices will bear down on a 71-foot bridge beam made of ultra-high performance concrete until the beam fails in what researchers expect will be an explosive crack.

The break test will begin at 10:30 a.m., Thursday, June 9, in Iowa State's Structural Engineering Research Laboratory in Room 164 of the Town Engineering Building. Brent Phares, associate director of the Bridge Engineering Center, said it's impossible to predict exactly when the beam will break. He said the testing could take several hours.

Phares said he expects it will take 750,000 pounds of load to break the beam.

Once researchers complete their tests, a similar beam will be used this summer to construct a bridge on 100th Avenue over Little Soap Creek in southeast Iowa's Wapello County. It will be the first time engineers will use ultra-high performance concrete in an American bridge.

Ultra-high performance concrete is made from sand, cement, water and small steel fibers. It does not contain the coarse aggregate typically found in standard concrete. Because the ultra-high performance concrete is engineered to include finer materials and steel fibers, it's denser and stronger than standard concrete.

Ultra-high performance concrete costs more than standard concrete, Phares said. But it also lasts longer. If the new material is more widely used over the next five to 10 years, he said it's likely to save costs.