Three-Dimensional Characterization and Evaluation of Aggregate Skeleton of Asphalt Mixture Based on Force-Chain Analysis

Aggregates in contact constitute the skeleton of the asphalt mixture and affect load transmission in the mixture, which determines its deformation resistance. The objective of this study is to characterize the aggregate skeleton for the evaluation of the stability of the asphalt mixture. The methodology has four main steps: (1) aggregates in specimens are three-dimensionally (3D) reconstructed before surface triangulation; (2) the geometry and orientation of contact areas between aggregates are detected to obtain the contact network of aggregates; (3) effective contacts are identified to determine force chains represented by a weighted directed graph; and (4) all force chains constitute the aggregate skeleton, which is then evaluated for load transfer efficiency by the characterization of the skeleton. Simulations of compression tests on three virtual specimens with different skeletons were conducted to obtain the stress and strain distribution within the mixture. The results indicate that a skeleton with a higher evaluation index has a more uniform stress and strain distribution, which indicates that the mixture bears the load better to resist deformation. The proposed method also facilitates the study of the correlation between the mixture stability and the gradation and morphology of aggregates.