A team from the University of Utah has created a process to rebuild roadways and restore bridges within a matter of days, not weeks.

Typically, bridges are built with columns meant to withstand the majority of damage of an earthquake at the top and bottom of the columns, where they meet the horizontal beams and the foundation. If the bridge survives the quake, but the columns sustain damage, the bridge may be unsafe to use. If the concrete has sustained damage but the steel rebar has not, traditional methods have been to chip away the concrete, reset the rebar and pour new concrete into a cast built around the column. This method can take weeks to complete.

Engineer Chris Pantelides and a “donut” repair to a bridge column. Image Credit: Dan Hixson/University of Utah College of Engineering.The Utah team’s new method uses concrete "donuts" built around the top and bottom of the column that are filled with a carbon fiber-reinforced polymer made of fibers and resin. Steel rebars are drilled in the foundation around the column and are secured with epoxy. Two halves of a shell, millimeters thick and made from the composite, are placed around the column and rebar and spliced. Concrete is then poured around the column and rebar as the composite fiber acts as a mold. The repaired column has approximately the same structural integrity as the original, the team says.

The donut shape provides the best strength for the amount of material used, and it distributes stress equally around the column. Future earthquakes should not harm to the column, giving the bridge a second life. The technique is usable immediately for damaged structures, and can be used to retrofit bridges to make them safer in the event of an earthquake.