Ants on an ant hill

Case Studies
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A new bridge is in the process of being constructed over the interstate at Atlanta’s 14th Street. Making room for the new structure’s center support column required the moving of seven interstate lanes approximately 60 ft to the west. The construction site was located at the north end of the downtown connector, where I-75 and I-85 come together, with the roadwork portion having been approximately 1,500 yd in length.

This project scope also included lowering the grade of about 700 ft of the seven southbound lanes by 30 in. at the maximum point to take a “hump” out of the interstate. To accomplish this, the company had to cut just over 5 ft deep at the peak of the cut.

To handle traffic flow, two lanes of I-75 were moved over on the weekend of Aug. 15 to new pavement previously built behind a barrier wall. I-85 traffic used a detour along the old Techwood Drive ramp during the Labor Day Weekend, when the main thrust of the project took place, beginning at 9 p.m. Aug. 29. The company would be assessed a $10,000-per-hour penalty should they be unable to finish and be off the road by 5 a.m. Sep. 2.

Cutting 10 in. deep at one time, four half-lane mills went to work, among them three Roadtec RX-900s . Approximately 23,000 tons of asphalt, aggregate base and soil were removed and 40,000 tons of graded aggregate base (GAB) and asphalt were placed during the two weekends.

After the milling operation, 8,000 tons of GAB were put back 14 in. thick on the milled surface that had been held by the cold planers to within +/- 1 in. of spec grade. Fine grading was accomplished with a motor grader and loader.
On top of that went a GDOT spec 25-mm, 12-in.-thick base course using three Roadtec pavers and three Roadtec Shuttlebuggy material transfer vehicles (MTVs), paving 12 ft wide.

The pavers and MTVs then came back with 3 in. of 19-mm asphalt binder on top of the base course, followed by 1.5 in. of stone-matrix asphalt (SMA).
Once the bridge construction is complete, a second 1.5-in. layer of SMA will be applied and finished with a final topping of 1.25-in. porous European mix.

C.W. Matthews Vice President of Asphalt Operations Bill White said his teams have had several planning meetings and communicated down through the organization exactly what was expected of everyone. The company was provided an equipment staging area adjacent to the worksite and had at least one backup for each critical piece of equipment.

All service support was provided by the company’s own shop personnel and, according to White, they fortunately had very little mechanical difficulty throughout.

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