Mechanism-based evaluation of compactability of asphalt mixtures

Compaction of asphalt mixtures is a critical component of the construction process of asphalt pavements. The quality of compaction has a significant consequence for the durability of asphalt pavements. Compaction of asphalt mixtures is a complex physical process, which has not been fully understood. In this study, we investigate the physical mechanisms of compaction, based on which we propose a new method to evaluate the compactability of asphalt mixtures. Two mesoscopic physical mechanisms are introduced. One is related to the jamming of aggregates, which governs the densification process of the mixture. The other is related to the binder-aggregate interaction, which is responsible for the change of shear resistance of mixtures during compaction. Based on these mechanisms, different indices are proposed to characterise the compactability of asphalt mixtures. The model is applied to analyse seven asphalt mixtures that were used to construct test sections at MnROAD research facility. Statistical analysis is performed to identify correlations between the compactability indices and material compositions, such as gradation and binder content. Based on the most significant correlations, multiple linear regression models are developed, which can be used to design more compactable mixtures.