Investigation on the Contributing Factors on the Fatigue Response of Bituminous Mixtures with Packing Model–Based Aggregate Gradations

The present study focuses on evaluating the contribution of aggregate gradation toward the fatigue resistance of bituminous mixtures. The fatigue resistance of bituminous mixtures with five different gradations was investigated using four-point beam bending tests. Two particle-packing approaches were adopted to design the aggregate gradations, in which the first approach does not account for aggregate interactions explicitly, and the second accounts for aggregate interactions implicitly. Fatigue resistance of mixtures with particle-packing-based gradations was compared with a bituminous mixture prepared with conventional dense-graded gradation. The samples were subjected to sinusoidal loading at 10-Hz frequency at 20°C for strain levels of 400, 600, and 800 μϵ. The collected test data were postprocessed using conventional and energy-based approaches to quantify fatigue life. The phase angle, Lissajous plots, and energy dissipation analysis were found to be good candidates because they are sensitive to capturing the effect of aggregate gradation for fatigue performance of the mixtures. It is seen that the mastic volume is designed rationally based on particle-packing approaches and that the nature of gradation influences fatigue life substantially. Mastic volume passing 300 μϵ was found to have a direct correlation with the fatigue performance of the mixtures.