Balanced Design of Asphalt Mixtures

A balanced mix design (BMD) sets a maximum asphalt content based on the rutting criterion and a minimum asphalt content based on cracking criterion. This project developed a BMD framework for the Minnesota Department of Transportation (MnDOT) and used it to evaluate materials from four Minnesota projects using the Illinois Flexibility Index; the IDEAL-CTAL-CT-CT Cracking Test Index by the Texas A&M Transportation Institute; and the Disk-shaped Compact Tension test for cracking and the Hamburg Wheel Tracking test for rutting. For the four test mixtures; the performance tests and the BMD procedure were successful in distinguishing the influence of asphalt content on cracking resistance and rutting resistance. There was fairly good agreement among the cracking tests for the asphalt content and only a slight deviation from volumetric asphalt content in most cases. The cracking and rutting performance criteria need to be refined for different applications based on characteristics such as climate; lift thickness; traffic level; and placement within the pavement structure.