Multiscale modelling and characterization of adhesion between bitumen and aggregate

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This project has focused on the bitumen-aggregate interface system known as the adhesion properties that have an intense connection with the micro-damages formation and the moisture susceptibility in asphalt mixtures. Two main research concerns have guided this project. The first one asks about the chemical and morphological heterogeneities of aggregates and their influence on the bitumen-aggregate interface performance. The second question revolves around the macroscale performance prediction based on the micro-mechanical (constitutive) model in the face of varying environmental and loading conditions.The research content is divided into five work packages: The first work package applies a comprehensive investigation on the rolling bottle test (currently used approach) taking into account different combinations of bitumen and aggregates. The energy-based method involved in the second work package is carried out to quantitatively describe the adhesion property between bitumen and aggregate. The interfacial adhesive energy of the bitumen-aggregate system, as well as the surface free energy of bitumen and the aggregate respectively, are measured by the contact angle test. The third work package introduces the molecular dynamic simulation into this project to study the bitumen-aggregate interfacial behavior at an atomistic level. For this purpose, chemical tests, including the thin-layer chromatography and X-Ray diffraction are performed to feature the chemical and mineral compositions for bitumen and aggregates respectively. In the fourth work package, Dynamic Shear Rheometer platform is modified with the concept of replacing the steel testing plates with real aggregate plates so that the mechanical property of bitumen-aggregate system can be directly measured. Consequently, the development of micromechanical damage model for asphalt mixture concerning the bitumen-aggregate adhesion can be achieved. Finally, in the fifth work package, the Finite Element simulation incorporating the micromechanical damage model developed in the fourth work package is performed to map the micromechanical properties onto the macro mechanical performance characteristics of asphalt mixtures and to predict asphalt (adhesion) material behavior.Combining the five work packages reveals a basic framework (comprising experiments and computational simulations on different scales) that relates the most important elements regarding the bitumen-aggregate system. The anticipated achievements of this project will contribute to the fundamental understandings of adhesion mechanisms between bitumen and aggregate and will allow for significantly improving predictions of asphalt performance on the macro level.