Determining the Service Life of Thin Hot-Mix Asphalt Overlay by Means of Different Performance Indicators

The use of thin hot-mix asphalt (HMA) overlay as a preventive maintenance treatment is gaining wide acceptance in the United States and abroad. Pavement management and maintenance practitioners seek quantitative means to assess the effectiveness of this and other treatments to plan, program, and budget for pavement preservation in the long term. A synthesis was done of studies on thin HMA overlay service lire. The service life of thin HMA overlay treatments applied in a midwestern state in 2001 to 2006 is discussed. The study, carried out separately for three functional classes-Interstates, non-Interstate National Highway System (NHS), and non-NHS-uses three performance indicators. They are the international roughness index (IRI), pavement condition rating (PCR), and rut depth (RUT). The study finds that the thin HMA treatment service life is 7 to 10 years (basis of IRI), 7 to I I years (basis of PCR), and 8 to I I years (basis of RUT). These values are based on the application of the following thresholds: 110 in./mi (IRI), 85 (PCR), and 0.25 in. (RUT), respectively. With the use of the survival model, a probabilistic approach was tested to capture the stochastic nature of the postoverlay deterioration and thus to investigate the variability in the life of that treatment. Furthermore, results suggest that the service life of thin HMA overlays is nonlinearly related to traffic loading and that differences in climatic severity can have a significant impact on the service life of the treatment.