Mechanistic Assessment of Fatigue Performance and Cost Analysis of Pavement Overlays: Comparison between Conventional Hot Mixed Asphalt, Asphalt Rubber, and Polymer-Modified Mixtures

Fatigue cracking, which is commonly associated with repeated traffic loading, is considered one of the major distresses occurring in asphalt pavements because of the low tensile strength of hot mixed asphalt (HMA). Studies have shown that introducing modifiers, such as rubber and polymers, increases the tensile strength of HMA, prolonging the fatigue life of pavement. Although research in the past has studied the effect of added rubber and polymers on the long-term fatigue performance of newly constructed pavement, few studies have shown the effect of those modifiers on the fatigue life of an asphaltic overlay and their associated cost-effectiveness. In this study, the long-term fatigue performance of asphalt overlay was constructed utilizing three different mixtures, conventional HMA, asphalt rubber (AR), and polymer-modified mixtures, which were evaluated utilizing 3D Move Analysis software. In addition, cost-effectiveness analysis was performed. Eighteen 3D Move Analysis scenarios were run including two different overlay thicknesses, three different vehicle speeds, and three different overlay mixtures. The tensile strain at the bottom of the overlay was determined and the number of fatigue loading cycles to failure (Nf) was calculated based on strain-Nf relationships of the three asphalt mixtures. Based on these analyses, use of modified mixtures as an overlay resulted in a significant increase in the service life of the overlay. It was demonstrated that AR and polymer-modified mixtures had better fatigue life and were more cost-effective than the conventional HMA mixtures.