Performance assessment of ultra-thin asphalt treatments in Louisiana

Ultra-Thin hot-mix asphalt concrete overlay (UTO) is a pavement maintenance treatment that is becoming increasingly popular among transportation agencies due to the resulting improved ride quality and reduction in noise. However, there is limited literature related to the long-term field performance of UTO treatments in hot and humid climates. The objective of this study was to assess the short- and long-term field performance of UTO treatments over asphalt pavements in Louisiana. To achieve this objective, Louisiana Department of Transportation and Development (LaDOTD) was contacted to identify all the UTO projects that were constructed over asphalt pavements in Louisiana before 2010. A total of seven projects were identified, and relevant pavement performance data and project information were retrieved from LaDOTD Pavement Management System (PMS) over a monitoring period of at least 14 years. The retrieved data were analyzed to determine the short- and long-term field performance in terms of the Performance Jump (PJ) and increase in Pavement Service Life (ΔPSL), respectively. The results indicated that the UTO had a significant immediate impact on all the surface distresses, restoring them to like-new conditions. The results also indicated that the UTO extended the pavement service life of asphalt pavements by 0.7 to 21.5 (average of 8.8±3.6) years according to the pre-treatment pavement condition and truck volume. It was concluded that benefits of UTO are maximized when applied to pavements with Pavement Condition Index (PCI) in the range of 60 to 70. It was also concluded that the benefits are maximized when UTO is applied to pavements subjected to lower truck volume (in range of 0-500)