In the United States, 53 percent of all the roads are unpaved. That translates into 1.6 million miles of unpaved roadways most of which are gravel roads. Currently they are being exposed to increased amounts of agricultural and industrial traffic. Also the problem of fugitive dust causes the loss of fine, binding material which increases the amount of floating aggregate and the tendency to develop washboards or corrugations. With use, fine and course portions of the aggregate segregate which also diminishes road performance. As the aggregate sources have been depleted and reduced in quality, unpaved roads increasingly have performance and economic challenges. The use of Recycled Asphalt Pavement (RAP) on gravel roads helps to improve the overall performance and life. Past studies also show substantial dust reduction when RAP is included in the road surface. However no clear relationship or methodology has been established to understand the connection between the RAP percentage and performance.A primary objective of this research project is to assess RAP as a material that can be incorporated into unpaved road surfaces to reduce dust, wash boarding, and their negative effects on performance. Case study on Recycled Asphalt Shingle (RAS) road sections was performed to understand the interaction of asphalt binder and gravel roads, results suggest that an optimal binder content percentage should be targeted for best performance. A subsequent laboratory test program was conducted on various RAP mixes to draw comparisons. This was followed by construction of test sections in Minnesota and testing of the performance of the road on the ground. This investigation attempts to identify factors can be traded off between RAP percentage, road performance, environmental sustainability and economic feasibility in order to achieve the goals of the road agency.
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