Special to The Daily Reporter
Through the scrape of plows in winter and the sizzle of sun in summer, Wisconsin’s roads take a beating. But it’s the change in seasons, more than the weather, that leaves roads worse for wear.
The hot-to-cold fluctuations necessitate repairs to cracked pavement, sinking manhole covers and rusting bridge reinforcements, among other things.
“The real challenge is that freeze-and-thaw cycle,” said Mike Paddock, a project manager for CH2M Hill Inc. who worked on the Marquette Interchange project. “When snow and ice thaw, water gets in small cracks in the pavement, and when it freezes again, those cracks expand. In the transition months of spring, this freezing and thawing can cause a lot of damage.”
Hot weather is a cause for concern too, said Steve Krebs, chief materials management engineer with the Wisconsin Department of Transportation.
“In the summer, the road swells and pops and we get concrete blow-ups,” he said.
Experts constantly re-evaluate road construction design and methods in an effort to achieve longer-lasting results and find the most bang for the taxpayer’s buck.
WisDOT is working on new technologies to help alleviate cracking and provide more support for roads in the high heat. Smart construction and design practices are part of that effort, Krebs said.
For example, to avoid sinking manhole covers, which can cause potholes, WisDOT tries to avoid putting manholes in vehicles’ wheel paths.
Starting from the ground up
Improving quality includes improving pavement-design methods to increase asphalt longevity.
When designing the Marquette Interchange project, Paddock said, “people did not want us going in and doing all this work just to have to do it again in the near future.”
As such, CH2M Hill used an asphalt paving design new to Wisconsin. It reversed the road’s design, putting the weaker pavement layers on top and increasing the strength of the bottom layers.
“With the old design, it would fail because a crack would occur at the bottom where the asphalt meets the gravel base and go up,” Paddock said. “So even as we repaired from the top, the crack was always there underneath and could easily reopen.”
With the reversed design, cracks are more likely to start at the surface. This allows crews to shave off the top couple of inches of pavement when a crack occurs and put a new layer of asphalt over the stronger base, Paddock said.
Using the right material is critical, too, said Doug Senso, transportation project manager at R.A. Smith National Inc.
“In the last 10 to 15 years, the development of polymer-modified asphalts has helped,” he said.
The modifiers yield asphalt that performs better in low and high temperatures.
“That is extremely important when you experience the temperature extremes we have in states like Wisconsin,” Senso said.
Winter weather wreaks havoc
A nasty effect of winter weather is the corrosion caused by salt used to de-ice Wisconsin’s roadways. The salt, combined with melting precipitation, migrates through concrete reinforcements on bridge decks. That mixture was a “killer” on the original Marquette Interchange decks, Paddock said.
“This time, we really wanted to make it last, so we used a high-performance concrete mix with low permeability and coated the reinforcement bars with epoxy to prevent rusting,” he said.
Advances in material technology led to the creation of concrete pavement with low permeability, which translates to less wear and tear on roads as a result of the freeze-thaw cycle.
And using stainless rather than regular steel for the dowels connecting joints in the road significantly reduces rust, Paddock said. Though more expensive than regular steel, stainless steel provides longer-lasting results, he said.
“We may end up paying 10 to 20 percent more, but may also get an extra 25 years out of the work as a result,” Paddock said.
Compounding the difficulty of Wisconsin’s changing weather is the fact that road work can’t be done year round.
“The main overriding factor in designing roads in cold weather states is the design needs to be on schedule because of the limited window to build,” said Senso.
And when construction is under way, there’s pressure to get the work done quickly.
“The overwhelming message we hear from the public on road work,” Paddock said, “is ‘Get in, get out and stay out.’”