Laboratory Evaluation of Thin Asphalt Concrete Overlays for Pavement Preservation
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A significant percentage of the existing lane miles of roadways in the United States, and in particular in Nevada, consists of rural roads. Thus, using a cost-effective pavement surface treatment becomes critical and essential in reducing maintenance and preservation costs on rural and low volume roads. The overall objective of this study was to assess the use of locally available materials in Nevada for the development of a durable fine-graded thin hot-mix asphalt (HMA) overlay mixture for pavement preservation. Accordingly, a comprehensive laboratory evaluation was conducted. The investigation considered establishing two mix designs using typical local materials for the northern and southern part of the state. For each mixture, the determined optimal binder content based on volumetric properties was varied within the allowable tolerances to simulate the potential variation in asphalt binder content during plant production. The performance of the two thin HMA mixtures were then evaluated at the various asphalt binder contents in terms of their resistance to moisture damage, resistance to surface raveling and abrasion, dynamic modulus property, resistance to rutting, and resistance to reflective cracking. Furthermore, the workability of the designed thin HMA overlay mixtures using the locking point concept in addition to the developed interlayer bond strength using the Louisiana Interlayer Shear Strength Tester were evaluated. Overall, both designed fine-graded mixtures showed a very good performance and are expected to perform well when used as a thin HMA overlay in Nevada. In particular, good stability, very good resistance to surface raveling and abrasion, and excellent resistance to reflective cracking were observed for both thin HMA overlay mixtures at all evaluated asphalt binder contents. A cost analysis was also conducted between the thin HMA overlay and a typically used pavement surface treatment. Based on the findings from this study, it was recommended to construct field test sections in various parts of the state to evaluate the field performance of the developed thin HMA overlay mixtures in Nevada.