Thin Open-Graded Friction Course Overlays in Cold Climates

Abstract: Thin asphalt overlays are widely recognized for their effectiveness in preserving both asphalt and concrete pavements. While most thin overlays (thinlays) consist of dense-graded mixtures, open-graded friction courses (OGFC) have shown promising performance in various applications. However, the literature addressing OGFC performance in cold climates remains limited, with consensus indicating that these mixtures often face challenges related to maintenance costs and susceptibility to winter maintenance activities, such as salting and snowplowing. This study aimed to evaluate the field performance of OGFC thinlays in a cold climate. Specifically, OGFC thinlays in Minnesota, a region characterized by severe winters. Four test sections were constructed over two types of existing pavement: two over hot mix asphalt (HMA) and two over Portland Cement Concrete (PCC). For each pavement type, two sections were constructed using either trackless or regular tack. Performance metrics included visual surveys to assess the Pavement Condition Index (PCI), International Roughness Index (IRI), and permeability measurements. After nearly eight years, visual assessments indicated that the sections remained in satisfactory condition, with average lifespans to poor condition estimated at 10 years considering PCI and over 10 years considering IRI. Notably, the permeability of the OGFC mixtures decreased significantly over time, with a marked decline occurring within the initial years of service. This research contributes valuable insights into the long-term performance of thin OGFC overlays in cold climates, suggesting the potential for successful implementation of OGFCs in cold climates despite the inherent challenges.