Effects of morphological characteristics of aggregate particles on the mechanical behavior of bituminous paving mixtures

• HMA rutting resistance is strongly correlated with coarse aggregate morphology.
• Direct and objective measurements of aggregate shape should be pursued.
• Shape properties characterized at AIMS 2 strongly correlate with rutting resistance.
• Surface texture should be considered in aggregate and HMA specifications.

This study evaluates the influence of morphological properties of aggregates on the mechanical behavior of bituminous mixtures. For that, two aggregates with different characteristics, i.e., round river gravel and crushed gneiss, were used in the research. Laboratory tests were conducted to characterize morphological properties of the aggregates following traditional methodologies and using a modern image analysis system, AIMS 2. Six asphalt mixtures containing different proportions of gravel and crushed gneiss were designed according to the Superpave methodology and evaluated in mechanical performance tests. The results obtained indicated that aggregate morphological characteristics, especially those of coarse particles, are strongly correlated with the resistance to rutting of the asphalt mixtures. In addition, AIMS 2 was shown to provide more direct and scientific measurements of aggregate morphological characteristics that present higher correlations with the mixture performance than traditional methodologies. Finally, the results also demonstrated that the aggregate surface texture is highly correlated to the performance of the mixtures and should be carefully considered in aggregate and asphalt mixture specifications.