Why Do Concrete Roads Buckle?

You've heard the expression, "crazy from the heat."

Well the heat can cause some crazy things to happen. For instance, concrete roads that begin to buckle when temperatures begin to really rise.

That was the case in Sioux Falls on Thursday, June 9, 2016. At least four different spots on roads within the city began to buckle as temperatures reached well into the 90's. The damage was keeping the city's street crews busy throughout the afternoon.

One spot, located at 12^th Street near I-29, received the worst damage. Traffic was blocked off on the lane, and drivers were urged to slow down.

Excessive heat can cause concrete slabs to expand. But why?

The answer, thermal expansion and contraction.

Materials expand or contract when subjected to changes in temperature. Most materials expand when they are heated, and contract when they are cooled. Concrete expands slightly as temperature rise and contracts as temperature fall. Problems develop in massive structures and roads where heat cannot be dissipated. Temperature changes that result in shortening will crack concrete pieces that are held in place or restrained by another part of the structure, internal reinforcement or by the ground.

A great example of this is a long restrained concrete section that drops in temperature. As the temperature drops, the concrete tends to shorten, but cannot as it's restrained along its base length. This causes the concrete to be stressed, and eventually crack.

Joints are the most effective way to control thermal expansion cracking. Control joints are grooved, formed, or sawed into sidewalks, driveways, pavements, floors, and walls so that cracking will occur in these joints and not in a random manner. Contraction joints provide for movement in the plane of a slab, and induce cracking caused by thermal shrinkage at pre-selected locations.

With hot temps expected again in most areas throughout the Sioux Empire this weekend, my guess is we can expect to see more thermal expansion happen.