Field Performance Assessment and Unsupervised Modeling of Thin Asphalt Overlays as Preservation Treatments for Highway Pavements, a Case Study

Thin asphalt overlays are a popular preservation treatment for asphalt and composite pavements due to their ability to address multiple pavement distresses. Their efficiency depends on several components such as traffic, climate, and the pavement condition at the time the treatment is applied. Nevertheless, typical life expectancy for thin overlays ranges between 7 and 12 years. Significant traffic volumes experienced on highway tend to accelerate pavement deterioration. Therefore, this study aimed to evaluate the field performance of thin asphalt overlays through several surface indicators such as rutting, cracking, and roughness. Data from the Pavement Preservation Group Study, a broader research study conducted by the National Center for Asphalt Technology and the Minnesota Department of Transportation's Road Research Facility was utilized. Specifically, control sections (untreated) and thin overlays placed on highway pavements at two different geographic locations, with distinctive climatic conditions, were studied. A k-means cluster and principal component analysis were performed to group sections with similar performance since various thin overlay configurations and combinations with alternative pavement preservation treatments have arisen. The findings revealed that thin overlays as preservation treatments contribute to maximizing pavement service life, maintaining roughness in good condition (International Roughness Index, IRI below 1.5 m/km even after 6 years), and decreasing its progression by up to 84% compared to untreated sections. These benefits were dependent on the respective pre-treatment condition and treatment configuration. Additionally, climatic conditions in each specific region play a crucial role in determining treatment performance.