This summer a lot of road construction has been happening along Highway 141 in Mapleton. This process is called Dowel Bar Retrofit with diamond grinding.

The roadway is an 8- to10-inch deep concrete pavement constructed in the 1960s and 1970s. The original construction placed joints in the pavement to control where the concrete cracks, but did not include any reinforcing steel at these joints.

“We now include reinforcing steel at the joints to help transfer the vehicle loads from one panel to the next,” said Dean Herbst, Sioux City Resident Construction Engineer Highway Administration with the Iowa DOT. “Otherwise, the joint will fault (be uneven from one side of the joint to the other) when the reinforcing steel is not included. This faulting can be felt by the driver as a thump when the vehicle crosses each joint.”

The Dowel Bar Retrofit process cuts slots in the pavement at wheel paths, which cross the joint.

“Then reinforcing steel is inserted in the slot and the slot is filled with a concrete mix,” Herbst said. “Essentially, the process adds the reinforcing steel without tearing out every joint. The roadway then will have diamond grinding to remove the faulting and other imperfections and create a smooth driving surface.”

He noted there were some areas where the pavement was deteriorated, and those area were patched instead of the dowel bar retrofit process.

The entire length of the project will have the diamond grinding to create the smooth finished surface.

Construction on this project started in mid-June and Herbst anticipates the project will be completed by the end of the week.

The prime contractor for the project is Iowa Civil Contracting, Inc. from Victor. They performed the patching and the dowel bar retrofit. Diamond Surface Inc. from Roger, Minn., is a subcontractor performing the diamond grinding and Iowa Plains Signing, Inc. from Slater is performing the traffic control.

Herbst said the contract value for this work is $808,578.27.

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