Optimal RAP Content for Minnesota Gravel RoadsStatus: CompleteReport Date: 03/13/2019 Summary: Researchers examined mixtures of recycled asphalt pavement (RAP) and aggregate for new gravel road surface layers in the lab and in the field. Test results did not align perfectly, and field results were somewhat uneven. However, findings suggest that mixtures with 70 percent RAP content can reduce dust generation and after a year of service can match all-aggregate gravel road performance in terms of strength, but with a smoother ride. Final Deliverables: Optimal RAP Content for Minnesota Gravel Roads (Report #2019-11) Study Suggests 70 Percent RAP for Minnesota Gravel Road Surfaces (Research Summary) Related Materials: Study Suggests 70 Percent RAP for Minnesota Gravel Road Surfaces (Blog Post) Related Research: Project Personnel: Principal Investigator: Charles Jahren Technical Liaison: Joel Ulring Project Coordinator: Lisa Jansen Panel Members: Dan Sauve - Clearwater County Hwy Dept Eddie Johnson - Materials & Road Research Gerard Geib - Materials & Road Research Kris Lyytinen - Cass County Highway Department Melissa Cole - Materials & Road Research Mike Tardy - Carlton County Ronald Mortensen - Meeker County Hwy Dept./Engineer Terrence Beaudry - Materials & Road Research