Better Roads Staff
“The theory was that if they sawed and sealed joints in the bituminous pavement, it would control the cracking,” says Brad Cegla, an MnDOT construction engineer. “But because of the sawing and sealing on Highway 59, those joints faulted over the years. You got a bumpy pavement.”
To repair a 13-mile stretch of the two-lane road, MnDOT required milling to a depth of 1.5 inches, cold-in-place recycling to a depth of 3 inches, and two lifts of hot-mix overlays, each 1.5-inch thick. The initial milling assured the state that the height of the final roadway would only rise 1.5 inches above the original grade – an important factor to keep crossings and entrances close to the existing height.
Cegla says the state chose cold recycling because it would take out the faulted joints and prevent reflective cracking later on. “The thinking was to break up that reflective cracking from below, and provide a recycled layer between the original pavement and our new overlay,” says Cegla.
Anderson Brothers Construction of Brainerd, Minn., won a $3.5 million contract with MnDOT to rehabilitate the road. After the initial milling, a subcontractor, Midstate Reclamation of Lakeville, Minn., swung into action with its cold-in-place recycling train.
“Our crew managed to complete 2.5 to 3 miles each day, working 10-hour days,” says Andrew Dauk, Midstate’s project manager. “The specification for cold-in-place recycling called for temperatures to be 50 degrees and rising. We figured our production was pretty impressive, considering that average overnight lows for that time of year are in the low-40s and working daylight hours are at their lowest.”
A CMI-made PR1050 milling machine, working 14 feet wide, followed an asphalt tanker truck to lead off the recycling train and mill the pavement to a depth of 3 inches. The big mill fed a recycler with a screen deck and hammermill crushing system that reduced all material to 1.25 inches in size. “From there it goes into our pugmill and the PG 52-34 asphalt gets added at a rate of 2 percent,” says Dauk. “En route to the pugmill, a continuous weighing system weighs the recycled material. The weighing system is interlocked with a computer that meters out the asphalt at the correct rate.”
The recycling unit laid down the cold-recycled asphalt in a windrow, and a Cedarapids pickup machine lifted the material into a Vogele paver. Compaction followed. “We ran a pneumatic roller and a steel-wheeled roller running static,” says Dauk.
For paving the two lifts in the overlay, Anderson Brothers used a Blaw-Knox 3200 paver working 14 feet wide. A 40-foot ski, running on the mat’s centerline side, helped achieve smoothness. A Topcon electronics system controlled the screed. Two Caterpillar breakdown rollers each made three passes to help achieve density. The intermediate roller was a Caterpillar PS360C rubber-tired machine, and the finish roller was an Ingersoll Rand DD110.
“We earned a smoothness bonus for that project,” says Mike Niemi, senior project manager for Anderson Brothers. “We have very competent people on our crews and we have good equipment.”
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