Kandiyohi County uses aggregate base stabilizer on damaged county road
Contributed by SnowEx
| December 20, 2013 |
Located in central Minnesota, Kandiyohi County proudly maintains a 649-mile highway system, which includes 452 miles of bituminous roads and 197 miles of gravel roads, as well as 69 bridges.
In the mid-2000s, it became apparent that a certain 5.5-mile stretch of bituminous road was beyond the point of maintenance. As with many other roads, the stress of heavy truck traffic created a poor surface condition, which then puts the pressure on county engineers to develop a cost-effective plan for reconstruction.
The affected 5.5-mile section was part of County Road 7, which runs south to north in the western part of the county.
“The bituminous surface was in poor condition,” says Gary Danielson, county engineer. “So we had to reconstruct this segment to accommodate the projected average daily traffic count of 883. Much of this is heavy truck traffic.”
The original design of County Road 7 included 9 inches of MN Class 5 aggregate base and 5.5 inches of bituminous surface. The design included two 12-foot traffic lanes and 6-foot aggregate shoulders. This was the county’s standard 10-ton bituminous road design that had been successfully used for a long time by Danielson in Kandiyohi County.
For the new reconstruction project, however, Danielson looked to achieve the 10-ton standard with the goal of reducing reconstruction costs for the county. After discussing his needs with Terry Maier, president of Team Laboratory Chemical Corp. Inc. (Teamlab) in Detroit Lakes, Minnesota, he decided to try including an aggregate base stabilizer in his road specs.
“Our county had never used base stabilizers in any of its reconstruction projects before,” says Danielson. “This was new to us.”
The aggregate base stabilizer was Base One, which is patented and distributed by Teamlab. Base One is a liquid stabilizer designed to increase the performance, strength and stability of aggregate base material.
It can be used in a variety of applications, including new construction, reconstruction, chip seal application, full depth reclamation and gravel surface treatment. It can be applied using a few different methods, including full depth reclamation with injection capabilities or by using a water truck and the blade mix method.
By incorporating Base One into the project, Danielson hoped to increase the granular equivalency (GE) value of the aggregate base. GE is a value used in Minnesota designs, which is similar to Structural Layer Coefficient or Resilient Moduli used for other designs. He figured this would allow him to cut down the thickness of bituminous material, while maintaining a 10-ton design. If successful, the reduction of material would save the county a significant amount of money.
The reconstruction project began in 2010.
“The final design approach was to grade the project with 9 inches of MN Class 5 aggregate base and stabilize the top 4 inches of the base material with BASE ONE,” says Danielson. “Then, in 2011 we would add 4 inches of bituminous surfacing instead of 5.5 inches as included in the original design.”
However, during the grading process, Danielson encountered a slight hiccup in the project due to soft soils in the area.
“We experienced poorer than expected soil conditions in three areas,” he says. “Braun Intertec, an independent testing company, conducted deflection testing after the Base One application and determined that, in order to maintain a 10-ton capacity, the three problem areas would require more than 4 inches of bituminous.”
Instead of increasing the bituminous thickness as recommended from the deflection testing, Danielson tried a different approach to save money and further test the strength of Base One. He had the contractor place an additional 3 inches of aggregate base material in the three weak areas and stabilize it with Base One. Then 4 inches of bituminous surface was placed throughout the entire 5.5-mile stretch of County Road 7.
After completing the paving, Braun Intertec was brought back to conduct a deflection test on the final surface.
“Even with only 4 inches of bituminous surface, the deflection tests showed a 10-ton capacity for the entire road,” says Danielson. “The Base One made a significant difference in the GE value of the aggregate base material.”
The test results proved the potential of the base stabilizer to reduce costs.
“After comparing the original structure design cost to the final design cost, Kandiyohi County had a cost savings of $190,000 on the project,” says Danielson.
Since completing the County Road 7 project, Danielson has seen continued result from the base stabilizer. He hasn’t noticed any deficiencies in the road’s condition.
“We’ve had no maintenance issues,” he says.
Additionally, Danielson has looked for other ways to implement Base One in the county.
“We had a similar project on County Road 8, but the aggregate in one area would not set up in the fall because there wasn’t enough clay passing the number 200 sieve,” he says. “Now, we require a minimum of six percent clay passing the number 200 sieve.”
Danielson has also used Base One on a variety of gravel roads that experience heavy traffic. The stabilizer helps keep the gravel in place, which saves maintenance costs by reducing how often he blades the road and the need to re-gravel.
Most recently, he has tried applying Base One on a county road with a chip seal surface. The road is used by a large turkey operation, so it experiences heavy truck traffic as well.
While Danielson continues to experiment with Base One, it appears the stabilizer has a bright future in Kandiyohi County. With hundreds of thousands of dollars in savings experienced already, the next step is to continue to find more applications.
“We’ll continue to use Base One on selected projects,” Danielson says.
Contributed by SnowEx. snowexproducts.com