Asphalt pavement preservation is a tactic used primarily in the realm of low-volume roadways. It has helped municipalities expand road life, keep overall highway maintenance costs down, and keep residents relatively happy during their commutes to and from work and home.

The success of these programs, along with interest from the Federal Highway Administration, is now pushing the paving industry to focus on pavement preservation for high-volume roadways.

The National Center for Asphalt Technology (NCAT) at Auburn University is leading the way, implementing pavement preservation test plots on U.S. 280 in central Alabama. The highway is a major artery into the metro Birmingham area. (See sidebar below, “High-volume preservation method testing.”)

NCAT directed placement of these plots last summer, collecting performance data such as roughness, rutting and cracking. In addition to collecting this data weekly, they are also studying more long-term performance metrics (such as field permeability) on a quarterly basis.

The test is designed to be a “rational starting point,” in order to narrow down which pavement preservation techniques are the optimal combination of life-cycle costs and performance. The secondary goal is to use the data gathered to create guide specifications, and to recommend guidelines for pavement quality assurance testing and inspection.

NCAT’s partner in road research, Minnesota Department of Transportation’s Minnesota Road Research Facility (MnROAD), is also testing some of the same pavement preservation treatments on high volume roadways in Minnesota’s cold-weather climate.

“Our goal is to execute a single experiment with nationwide impact through the MnROAD partnership,” says Buzz Powell, NCAT assistant director and test track manager. “This involves experiment design, construction planning, installation, performance testing, dissemination of findings, and (most importantly) implementation. It would be ideal for guidelines/specifications to be universal; however, best practices could vary as a function of climate, materials, etc.”

Municipal experience

The Charleston County (South Carolina) Transportation Development department has been a model example of a municipality continually improving and expanding a preservation program. In honor of those achievements, For Pavement Preservation (FP²) awarded the agency its 2014 James B. Sorenson Award. FP² lauded the agency for its work testing and implementing multiple preservation techniques, and for its communication efforts explaining the preservation work to the public.

Though more than 80 percent of the county’s preservation work takes place on low-volume roadways, according to Richard Turner, project and preservation program manager, one method stands out for its effectiveness on high-volume roadways: microsurfacing.

“We continue to run pilot projects trying different applications, and probably the most used is microsurfacing,” Turner says. “I’ve seen that successfully placed on high-volume roads here in Charleston, by us or by the South Carolina Department of Transportation (SCDOT), assuming it’s put on the right road at the right time. If you put a microsurfacing treatment down on a road that’s a little bit further into its life, the microsurfacing lifecyle won’t be as good as it would be if you applied the treatment earlier in its life.”

This technique is fairly new in the market for high-volume roads in South Carolina, with SCDOT using the technique for the first time seven years ago (on U.S. 17 in Charleston County). Turner says his agency’s first use of the technique was in 2011.

“We’re looking at a market that’s five to seven years old,” he says, adding that he hasn’t been able to work with contractors in South Carolina because there aren’t any doing the work. Instead, contractors from adjacent states are winning the contracts.

“The two or three companies that are bidding on projects throughout South Carolina are able to have a nomad crew that comes and spends 30 to 60 days in each county, get the work done and report back. I don’t know if there’s anyone in the state ready to invest yet or not.”

From Turner’s perspective, microsurfacing is a far better application for high-volume settings (compared to low-volume roads), a viewpoint that comes as a direct result of his agency’s communication efforts. It boils down to look and feel.

“When it’s placed on roads that are higher volume, we’ve gotten no complaints,” he says. “When we’ve placed it on lower volume roads, that’s when we get the questions. It’s mostly because you have folks walking on these roads and they’re looking at every little detail of that road. They can tell that it’s not the same as a hot mix or dense graded asphalt. That’s when they notice it. When you’re driving down the road you can’t see it or feel it. You can’t tell that it’s any different.”

Placing a microsurface treatment on high-volume roads changes the esthetics of the mat, Turner explains, with more traffic improving its appearance within the first month of use. “The effectiveness of it doesn’t change one way or another, but from a public perception standpoint, I think it looks better on a high volume road,” he adds.

Public perception of microsurfacing has taken a hit from instances of improper placement, and also from the application being used as more of a temporary bandage. “Those roads needed much more than a microsurfacing or some other preservation treatment,” Turner says.

Turner’s point touches on a major concept of pavement preservation. A roadway in need of major work, or one that is failing, is not a good candidate for preservation work and requires more extensive rehabilitation. To paraphrase Marty Comer, the president of Comer Contracting in Connecticut, even in lieu of public opinion, preservation is a difficult concept for some municipalities to grasp.

“It’s a real tough sell,” he says. “Pavement preservation is for ‘good’ pavement, and to get people to spend money on good pavement is sometimes a challenge. In dealing with municipalities, it’s a tough sell when they have bad roads that need work and then they try and spend money on preservation work. That’s what the whole industry has been promoting for quite a number of years, but it’s still a tough sell.”

Contractor perspective

As in South Carolina, microsurfacing has emerged as the high-volume preservation of choice in Connecticut. And just like its southern counterpart, Connecticut faces a shortage of contractors to perform the task. Even as a pavement preservation specialist, most of Comer’s work is chip seal.

But, much of the preservation work in the state has been handled a different way. Connecticut has seen a strong run of resurfacing work over the past few years, with the state’s Department of Transportation recently reporting 2015 as the fourth straight year of increased two-lane road resurfacing.

“There was a lot of bituminous concrete (asphalt) put down last year as far as historical amounts, and they plan to do a fair amount this year,” Comer says. “ConnDOT has a tendency to call that pavement preservation, especially if it’s thin lift, because the paving industry has tried to make that the pavement preservation of choice.“

“The public will, to a certain extent, accept cape seal in this area with chip seal and microsurfacing over it,” he adds. “They still turn their nose up at it a little bit, but it’s perceived as more acceptable because it’s smoother. “

“The name of the game in any surfacing project is to avoid having loose stone. For instance, if you’re going to chip seal, it needs to be swept practically the same day. That’s where I think it’s going, at least where I’m working. The motoring public doesn’t accept chip seal well, but if you can make it smoother, if you can sweep it up real quick, then the pavement maintenance industry can have more success. You certainly have to be neat and produce a good looking product.”