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How does a street buckle?

July 05, 2012|By Leonor Vivanco, RedEye

With the news of crews working to fix Columbus Drive, which buckled Wednesday north of Roosevelt Road due to the heat, we wondered: How does that happen?

Robert Seyfried, a civil engineer who is an adjunct instructor at the Northwestern University Center for Public Safety, generally explains how a street can buckle.

Concrete expands in the heat. A concrete-paved road is constructed with heavy reinforcing or what’s known as expansion joints, he said. They are spaces in the pavement surface measured at a half an inch to an inch wide between sections of concrete and typically sealed and resealed periodically with tar, he said.

Problems arise when those gaps aren’t wide enough or are clogged with dirt or debris like gravel.

“When concrete expands in the heat, it has no place to go,” Seyfried said. “The pressure builds up until something has to give and that’s when the buckling takes place.”

In very extreme heat like this, he said, concrete might expand even more than what was initially planned for when the road was built and thus needed more space that the expansion joints allowed. | @lvivanco

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