Center for Transportation Research and Education

About the research

Recycled Asphalt Pavement (RAP) has been used in several construction applications, including the blending of RAP with virgin aggregates in gravel roads. RAP is intended to reduce costs and offer environmental benefits through reduced consumption of natural aggregates, while adding cohesion, which can add strength and bind particles to reduce raveling and loss of aggregate. RAP can also reduce the permeability of the surface course by decreasing the void volume, which may have beneficial effects, such as reducing dust loss and creating tighter particle packing that aids stability. However, the beneficial effects of RAP may decrease over time as the oils in RAP dry out. Furthermore, RAP can make blading operations more difficult as the material adheres to the moldboard in hot weather or becomes hard and brittle in cold weather.

The objective of this study is to help agencies better understand the potential advantages and disadvantages of using RAP in gravel roads by synthesizing existing research, surveying local Minnesota agencies, performing field and laboratory tests on new and existing sections of gravel roads containing RAP, and conducting a life-cycle cost analysis (LCCA). The anticipated major benefits of this study will include a better understanding of the potential costs and benefits of incorporating RAP into gravel roads and other construction projects, as well as quantifying its performance in terms of permeability and drainage, oil concentration, plasticity, strength, stiffness, and surface distress issues over time. Deliverables will include a research report and a brief technology transfer guidebook detailing the findings.