Minnesota’s County Road No. 7 reconstructed to support 10-ton traffic

Minnesota’s Kandiyohi County Road No. 7 was in need of reconstruction.

“This segment of the grading and bituminous surfacing project was projected to receive a lot of heavy truck traffic with a projected [average daily traffic] of 883,” said Assistant County Engineer Ray Krossman.

The original structure design was 9 in. of MN Class 5 aggregate base and 5.5 in. of bituminous surface to carry 10-ton traffic. The goal was to eliminate 1.5 in. of the bituminous surfacing by using Team Laboratory Chemical Corp.’s Base One Aggregate Base Stabilizer to increase the Granular Equivalency (GE) value of the aggregate base material, maintain a 10-ton design, and have a cost savings.

The final design approach was to grade the project in 2010 with 9 in. of MN Class 5 aggregate base and stabilize the top 4 in. of the base material.

“During the grading project we encountered poorer soil conditions than expected in three areas of the project,” said Krossman. Braun Intertec, an independent testing company, conducted deflection testing after the application of the base stabilizer and determined that the three problem areas would require more than 4 in. of bituminous.

In 2011 Kandiyohi County placed an additional 3 in. of stabilized aggregate base material in the three weak areas and 4 in. of bituminous on the entire 5.5-mile project.

Braun Intertec conducted deflection testing on the final surface resulting in 10-ton capacity for the entire road.

After comparing the original structure design cost to the final design cost, Kandiyohi County had a cost savings of $190,000 on the project.

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