More, now than ever, importance on saving materials, time, and money is at the forefront of infrastructure maintenance. Large strides have been made to achieve these goals through the use of pavement preservation. A properly applied preservation method will extend the service life of the pavement, use less materials than a typical overlay or reconstruction, and result in lower construction costs. The presented research evaluates a variety of analytical methods used to model the performance of four different flexible pavement preservation methods, including microsurfacing, slurry sealing, patching, and crack/joint sealing.

Best-fit curves were applied to performance data from the Iowa Department of Transportation’s (DOT) pavement management system (PMS) to identify the pavement’s current rate of deterioration as well as the pavement’s response to the preservation method. These curves were collected across multiple projects of each preservation type, and the initial findings showed microsurfacing to have the longest service life extension, according to the pavement condition index (PCI), with a value of 3.7 years. Patching resulted in a 3.4-year extension, followed by slurry sealing (seals targeting only specific cracking) and crack/joint sealing, with service life extensions of 3.0 and 2.2 years, respectively.

Further evaluation of preservation timing and trafficking levels showed the microsurfacings were often being applied too late, likely a result of an economic-based decision-making governing performance-based decision making. Additionally, a split plot repeated measured statistical analysis significantly reduced the unnecessary variation from on project to the next to identify accurate estimations of true preservation effectiveness. Microsurfacing, slurry sealing, and patching all showed statistically significant improvements in PCI, riding performance, and cracking performance, while crack/joint sealing was the only preservation method shown to improve the project’s rutting performance. Lastly, economic analysis was applied to these predictive models to better understand the overall quality supplied by the preservation methods. The most cost-effective preservation method of the four was determined to be crack/joint sealing, followed by slurry sealing, microsurfacing, and patching, in that order. When comparing the costs to the quantity of improvement, however, slurry sealing and microsurfacing were substantially more cost-effective than crack/joint sealing and patching.