InTrans / Jun 17, 2020
Successful strategies for pavement preservation
Pavement preservation strategies help to save money and extend the service life of a road system, but there’s a secret to their success.
“It’s all about choosing the right pavement at the right time, and choosing the right treatment,” said Ashley Buss, assistant professor in the Department of Civil, Construction and Environmental Engineering at Iowa State University.
Buss recently wrapped up a research project published here that looked at the pavement preservation treatments used in Iowa and their effectiveness. She’s now working on developing a pavement preservation guide for Iowa agencies.
Right Pavement, Right Time
Buss recommends using the Road Resource Toolbox from the Pavement Preservation and Recycling Alliance to assess what pavement treatments will work best for the road condition.
The tool allows users to enter the pavement condition, primary distress, road type, and surface type, and then see what types of treatments would be most suitable for the roadway.
Buss also offers another secret to success: One does not simply preserve their worst pavement.
She said many stories about certain pavement treatments not performing well or not getting a full lifespan are due to poor pavement selection.
Other challenges include matching performance and project data to justify the treatment, limited quality assurance for non-hot mix asphalt (HMA) projects, and getting performance-related specifications.
As part of her research, Buss conducted a survey of Iowa counties to determine what treatments they were using. A total of 66 out of the 99 counties responded, showing crack sealing and crack filling were the most common and the ones that best works for agencies. They’ve also employed microsurfacing and slurry seals.
Buss noted that some of the more minor treatments, such as those most commonly employed, should be used on roadways in better conditions. Though they don’t always give demonstrable data, Buss said those treatments showed marked improvements during in-person tours of counties.
“It’s too subtle to actually pick up on the full benefits,” Buss said. “For example, if we seal a crack, and it’s keeping the water out, the data aren’t going to be picking up on the benefit that the crack sealing is having on a crack by crack basis.”
She said the more expensive and invasive treatments show significant benefits in the data, but also carry the costs that can make them prohibitive for some counties. Buss endeavors to study those treatments that are relatively cost-efficient but also show demonstrable data, particularly slurry seals and microsurfacing.
She said data indicate microsurfacing treatments on average are extending pavement life by 5.5 years for Iowa roadways.
Pavement Preservation Planning
While acknowledging budget challenges, Buss also stresses the importance of having a dedicated funding stream specifically for preservation.
To do that, Buss plots out the steps. Planning starts by aspiring to the ideal program based on research from other agencies, then identifying needs, and then developing a vision. Implementation starts with intent and commitment and continues with data analysis to understand the return on investment.
The survey conducted as part of Buss’ research showed 50 agencies have an informal program, 8 agencies have a formal pavement preservation program but not dedicated funding, 3 have dedicated funding and policies, 3 have an informal program that is nearly non-existent, and 2 didn’t reply.
“Road work is something that is ultimately inevitable in the life-cycle of the pavement,” Buss said. “You’re going to construct that road, and its performance is going to decline over time, and then, it’s a cycle of having to come back and perform road work.”
Interested in more? Watch a webinar Buss recently did on this topic here, and read up on the research project here.