Three-dimensional balanced mix design for asphalt concrete

Improving asphalt concrete (AC) performance entails designing mixes that can withstand various environmental and traffic loading conditions. Rutting and thermal cracking are distresses associated with high and low temperatures, respectively, while fatigue cracking is a result of heavy load repetitions. These distresses can be considered during the AC mix design through laboratory testing. Current balanced mix design (BMD) approaches focus mainly on two trafficrelated distresses: rutting and fatigue cracking, and their results are presented in a twodimensional interaction diagram. Limited attention has been directed towards thermal cracking, which is an environmental related distress. This paper establishes a three-dimensional (3-D) interaction diagram to include material properties for AC mixtures that would yield exceptional performance against rutting, thermal cracking, and cracking at intermediate temperature. The interaction diagram was constructed using three tests: Hamburg wheel tracking test (HWTT), Illinois flexibility index test (I-FIT), and indirect tensile test (IDT Creep). The tests were performed on three AC mixes, typically used in Illinois (N90-0, N70-0, and N70-10). Based on the 3-D interaction plot, N90-0 performed best on the I-FIT and IDT tests making it the overall highest performing mix. N70-0 on the other hand, performed the least in all the tests earning it the lowest overall performance.