June 2017 Vol. 25, No. 2

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Rehabbing roads with full-depth reclamation is cost-effective, durable

FDR local applications

Compacting and smoothing pavement is one of the last steps in FDR of urban and suburban roads.

Full-depth reclamation (FDR) of asphalt pavement is often used on rural roadways to reduce costs for materials and hauling. New research indicates that FDR is also a good option for rehabilitating urban and suburban roadways and most likely out-performs traditional mill-and-overlay in cost and durability.

With FDR, road builders use trains of recycling equipment to pulverize, lift, grind, remix, and repave asphalt in a single pass. This recycling puts less demand on petroleum resources and new aggregate. Despite its benefits, FDR has yet to be adopted widely by city and county public works departments. In part, this is due to the challenge of using trains of equipment on urban and suburban roads that feature curbs, manholes, and driveways. Mill-and-overlay also has lower initial costs.

“Our goal was to provide evidence of FDR’s cost-effectiveness, guidelines for FDR project selection, and, ultimately, performance-based specifications,” says Mihai Marasteanu, a professor with the University of Minnesota's Department of Civil, Environmental, and Geo- Engineering and the study’s principal investigator.

Researchers also sought to provide testing protocols, procedures for analyzing life-cycle costs of FDR compared with conventional rehabilitation methods, and ways to use the MnPAVE computer program to determine long-term performance expectations for FDR.

“When we compared the simulated life-cycle costs of FDR with known results for traditional mill- and-overlay mixtures, we found that FDR is more cost-effective over a 35-year period than traditional methods,” Marasteanu says. “In addition, mill-and-overlay must be redone every 18 years, causing more inconvenience and costs for road users than the longer-lasting FDR.”

The City of Shoreview has used FDR effectively by using individual machinery units rather than long, connected recycling trains. “This research helps us translate full-depth reclamation projects in Shoreview into hard cost-benefit, return-on-investment numbers,” says Mark Maloney, Shoreview public works director. “It validates what we’ve been doing and gives cities what they need to justify the cost of using FDR in urban settings.”

“Before, all we had was anecdotal information,” Marasteanu says. “Now we have laboratory testing methods that are easy to use and can be incorporated in performance prediction models.”

The project was sponsored by the LRRB and the Minnesota Department of Transportation.