Design Procedure for Bituminous Stabilized Road Surfaces for Low Volume Roads

Many low-volume roadways in the county road system in the State of Minnesota consist of unpaved aggregate surfaces. It is the responsibility of the county engineer to make determinations regarding the design and maintenance of such roads and particularly for specific needs, such as weight restrictions. One method used by several counties in Minnesota is the construction of a bituminous-stabilized layer by adding several inches of new aggregate and stabilizing it with an engineered, water-based asphalt emulsion using mix-in-place methods. This report describes a design method providing highway engineers and their staffs with the technical backing needed for the designs selected. This report describes the design method for determining the required thickness of stabilized and unstabilized layers in this type of aggregate-surfaced road. This basic design method is based on the material properties and a correlation between layered-elastic analysis, dynamic cone penetrometer, and falling-weight deflectometer testing. The load rating analysis uses the Minnesota Department of Transportation methodology of estimating load rating on low-volume roads using falling weight deflectometer data. A software package is also presented which was developed as part of this project.