The final report summarizes the work to develop a new specification, which included conducting a review of current ¾-inch minus specifications from around the U.S., using that
information to generate a preliminary specification to create ¾-inch minus mixes, testing the material properties of these mixes, and modifying these mixes to determine the effect changes in the gradation primarily had on its strength, stiffness and permeability. Based on the results of multiple statistical evaluations as well as qualitative
comparisons, it was concluded that a ¾-inch minus gradation specification will perform at least as well as Montana’s existing CBC-6A materials and better than CBC-5A materials. Gradation limits for a new ¾-inch minus, Grade 7A, crushed base course were suggested; however, the practicality of producing mixes that fit within the suggested gradation limits still needs to be determined.