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Engineers get inventive to improve local treatment of county road surfaces
Lansing, MI – As Michigan begins to collect its first new road funds in 20 years, the driving public may be interested to hear about the technological improvements passing under their tires. County road commissions and departments are constantly testing and adopting new solutions to make pavements last longer and address the special conditions that occur on Michigan’s 90,000 miles of local roads.
Some of those innovations being adopted by the Midland County Road Commission (MCRC) were highlighted in the recent Crossroads, the magazine of the County Road Association of Michigan.
MCRC managing director, Terry Palmer, PE, had listened to a vendor during a lunch-time training program at the Roscommon County Road Commission. The vendor talked about an atypical technology, which Palmer believed had potential to strengthen Midland County’s own road surfaces. Even better, the technology had already proven effective in different cities.
“I thought ‘someone has got to try it’,” said Palmer. “Anytime we can try to extend the life of our pavement at the same cost of your traditional fixes we like to try it.”
The technology in question was paving fabric, which can bring to mind landscape fabric – but for the road projects. Water, when it freezes, is the number-one enemy of Michigan roads. However, paving fabric works by sealing imperfect road surfaces against water in a way that strengthens the road surface as opposed to the traditional chip-seal method.
A relief layer is created by applying hot asphalt onto a uniform road base with a tractor, which lays down a surprisingly white fabric on top of the base. If there are a lot of pothole patches in the base, MCRC opts for a brand new asphalt wedge layer. Otherwise, 1.5 inches of asphalt pavement with a chip-seal finish is the best practice.
Paving fabric has been implemented on 2.2 miles of three different sections of Midland County road thus far. Palmer is optimistic about its return on investment.
“The cost of paving fabric is about the same as that of a chip-seal,” Palmer said. “Yet we’re hoping to get 15 years out of this project, about 50 percent more than the life of a typical overlay.”
Palmer, who became managing director in 2015, also tested another new technology this last year. With only 22 percent of Midland County’s federal-aid roads rated “good” and funding flat, Palmer was challenged to fix a relatively age-old problem in the area.
While driving down one of MCRC’s state concrete highways during the winter, Palmer realized that parts of it that were paved just 18 months earlier didn’t “ride well.” In fact, they “rode” the same as roads that hadn’t been paved in 20 years.
The underlying problem with these old state roads isn’t limited to Midland County, but is a function of “band aid” fixes over the years. These particular concrete highways had been “rubbleized,” or ground up many years earlier, due to extremely poor road conditions and then repaved over the top.
They were breaking down too quickly, and after much consideration Palmer decided to invest in three different road treatments.
The first two methods included micromilling the road surface to perfect it, putting down a fiber mat, and then either topping it with a thin ¾-inch overlay of asphalt or using asphalt emulsions and chip stones as a cover. Palmer had picked up the little-used fiber mat technology years earlier when he worked for the Michigan Department of Transportation.
“I remember that the fiber mat had seemed to slow down the cracking; cracks were back in 10 years, rather than five,” Palmer said.
The treatment that is yielding the best results is what Palmer has coined the “Sanford underbody.” This technique involves milling off 2 inches of the road surface, then applying a standard chip-seal and 1.5 inches of asphalt.
“After one year, the “Sanford underbody” has no cracks,” according to Palmer. “We’ll review it year after year, but it would be a nice easy treatment for road commissions to do. It is about 20 percent more expensive, but I expect it to last 50 percent longer.”
The inquiring mind of Terry Palmer, and the other road professionals across Michigan’s 83 county road systems are testing and implementing new techniques and materials every year to improve the road surface under drivers’ wheels, keeping the Michigan’s roads and bridges running smoothly.
Midland County Road Commission is one of 83 members of the County Road Association that represents the unified credible and effective voice for a safe and efficient local road system in Michigan, collectively managing more than 73 percent of all roads in the state—more than 90,000 miles and 5,700 bridges—the fourth-largest county road system in the nation.