With the 9-in. (23 cm) concrete overlay portion of the 13-mi. (208 km) Interstate project almost complete, MnDOT pushes to remain on schedule.
The $6.9-million westbound lane on Interstate-94 that runs from Sauk Centre, MN, to Osakis, MN, in west central Minnesota, was scheduled to be completed by Labor Day. MnDOT expects to have the project completed on time, said Micky Klasen, project supervisor with MnDOT, even though rain has delayed previous phases of the project.
So MnDOT escalated its operation by working longer days and a couple of Saturdays to make up some time, Klasen said. “We can also overlap operations if we need to.” The general contractor for the project is Progressive Contractors Inc., of St. Michael, MN.
Work actually began last fall with the construction of crossovers to divert traffic to the eastbound lane, which was refinished last year, Klasen said. Work resumed in mid-April this year with the installation of four culvert liners and one culvert replacement.
“We put in some culvert liners and used a spent grout to fill the void outside the liner, so it is virtually a new pipe system,” he explained. “Not removing the culvert and repairing the roadway brings the costs down.”
Also keeping the costs down is a decision to work with the existing concrete. Klasen explained the Interstate was originally constructed about 33 years ago, “but it is in good enough shape to utilize an in-place stress relief layer,” he said.
A 1-in. (2.5 cm) permeable stabilized asphalt stress release layer is poured over the existing concrete, which acts as a buffer over which the 9 in. (23 cm) of concrete is poured. Pouring the concrete will take about three weeks.
“That is the latest process the state has been using,” he said, adding there are a number of processes the state uses, depending on the condition of the existing concrete. Processes might include cracking the concrete and overlaying it, totally removing it and having it recycled, or doing a regrade or a granular upgrade.
To determine which process to use, Klasen explained that any project more than $5 million goes through a cost benefit analysis process by a materials engineer, to determine if the concrete is to be left or replaced. Many factors are considered, including the cost of recycling the concrete, and additional costs associated with the need to make a deeper cut to construct a new road, should the existing concrete need to be removed.
The same job may require using more than one process, he said. For example, under the bridges in this Interstate-94 project the concrete needed to be removed so a granular treatment is being used.
To control the quality of the pavement process, the paver is equipped with one of the latest standards, Klasen said — a vibrator. The vibrator consolidates the aggregate and the concrete so it doesn’t settle in too far, he commented. The process is monitored, graphed and the frequencies are recorded on a digital printout.
“The distances are also recorded where the paver is and at what time the readings are taken,” he added. “The purpose is to have a record.”
Recording the frequencies gives a high quality product a more controlled method of placement. “The method has probably been out there but probably not in concrete pavement,” Klasen said.
The next step on the Interstate-94 project after the concrete is poured, is to saw the joints and seal them, which takes about three days, Klasen noted. Sawing is done as soon as the concrete has cured. An edge drain will then be installed on both sides of the roadway, using a 4-in. (10.2 cm) edge drain that is located below both concrete layers. It takes the water from the joints to a tile line that runs on the edge of the concrete, he added. Outlets into the ditch are placed every 500 ft. (152 m).
Shoulders will then have to be stripped, removing the topsoil and then the shoulders will be raised with a class 5 aggregate base. A new slope will also be built on the shoulders, Klasen said. The shoulders will then be covered with a bituminous overlay. The left lane will be 3 ft. (.9 m) wide and the right shoulder will be 8 ft. (2.4 m) wide, allowing pullover room and room for a 2-ft. (.61 m) rumble strip to wake drivers up if they should veer off the main roadway. The rumble strip is put into the wet concrete.
Topsoil will then be placed to the edge of the bituminous and seeded. Striping will be the final phase before the roadway is opened to traffic.
After the Labor Day completion date, the crossovers will be removed, Klasen noted.
As always, safety is an issue on the project site. Mike Travis, public affairs director for MnDOT, said the department has incorporated the use of message boards, which are relatively new in the state.
“This is the first job we’re using them on,” he said. A permanent message board was placed at Monticello, a community about 65 mi. (105 km) from the construction site to notify motorists of the upcoming roadwork. Others are placed at Clear Lake and at St. Augusta.
The message boards are programmable by radio and can be changed right at the MnDOT office in St. Cloud, rather than traveling to the site each time a change is needed, Travis explained. Having fewer people at the construction site helps create a safer work environment. Incorporation of the signs by MnDOT occurred for winter road closures but they soon discovered the signs are handy for road construction, too, Travis added.
Letting the motorists know well in advance that a construction project is underway up ahead also provides them with some options, Travis said.
“I think if the traveling public is aware of what they are going to run into down the line they have a choice of detouring and they have a better mindset if they choose to remain on the roadway [where the construction is],” he added.
On this particular project, motorists have the choice of taking Highway 10 instead of the Interstate or they can take Highway 55 east or west and catch a north/south route like Highway 71, instead. “It [detouring] is just enough so traffic is manageable out there, even during the holidays,” Travis said.
Other construction projects are occurring along Interstate-94, north of the Sauk Centre to Osakis stretch, Travis noted, making the option of taking an alternative route more appealing. Those other projects include one by Rothsay, MN, about 30 mi. (48.3 km) from the Fargo/Moorhead metropolitan area, and one by Alexandria, MN, about 70 mi. (113 km) north of Sauk Centre, so within about 100 mi. (161 km) travelers will encounter three construction sites.
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