Is Seal Coating Counterproductive or Not?

While seal coating has been widely used as a cost-effective strategy in asphalt pavement preservation by MnDOT and local agencies with great success, some cities and counties in Minnesota have reported their concerns about the premature stripping of street pavements that have been seal coated. The objective of this study was to diagnosis whether seal coating was counterproductive in asphalt pavement preservation. In this study, the research team investigated the mechanisms accountable for asphalt pavement stripping under seal coats and provided recommendations. Comprehensive field and laboratory data collection was conducted to diagnose premature stripping. Some possible causes of stripping were proposed after preliminary diagnoses. For example, one proposed cause was that due to the weak bond strength of the asphalt pavement, the underlying seal coating could be prone to premature stripping under high-moisture and multiple freeze-thaw conditions. Corresponding laboratory testing was then conducted. Based on the research conducted in this study, it cannot be simply concluded that seal coating is counterproductive. This report is available online from the Minnesota Department of Transportation web site at https://www.dot.state.mn.us/research/reports/2020/202034.pdf