This study aims to evaluate the effects of mineral types and water on the adhesion properties and debonding behaviours of bitumen-mineral interface systems. A molecular dynamics modelling approach was employed to simulate the interactions between minerals and bitumen with and without the presence of water. Four representative minerals (quartz, calcite, albite and microcline) were selected to build the mineral-bitumen interface systems and the mineralwater-bitumen interface systems in the molecular dynamics models. The adhesion property between minerals and bitumen was quantified by work of adhesion, defined as the energy required to separate a unit area of the bitumen-mineral interface. The debonding behaviour between minerals and bitumen is characterised by work of debonding, defined as the energy required to displace bitumen by water at the mineral-bitumen interface. The simulation results were validated by available experimental results reported in the literature. It was found that the work of adhesion and the work of debonding for the four bitumen-minerals interface systems are ranked microcline > albite > calcite > quartz at both dry and wet conditions. Moisture can reduce the adhesion between minerals and bitumen by 82%, 84%, 18% and 1% for the quartz, calcite, albite and microcline, respectively. The adhesion between minerals and bitumen is attributed to the non-bond interaction energy, in which the major component is van der Waals interaction for neutral minerals (e.g., quartz) and the electrostatic interaction for the alkali minerals (e.g., calcite, albite and microcline). The bitumen-mineral debonding is a thermodynamically favourable process with reduced total potential energy of the system. It is concluded that the bitumen-mineral adhesion and debonding behaviours strongly depends on the chemistry and mineralogical properties of the minerals. This work provides a fundamental understanding of the adhesion and debonding behaviours of the bitumen-mineral interface at the atomistic scale.

The interfacial adhesion between oxidised bitumen and mineral surfaces at dry and wet conditions was investigated using molecular dynamics (MD) simulations. Molecular models were built for virgin and oxidised bitumen components including saturate, aromatic, resin and asphaltenes. The bitumen models and four representative mineral substrates (namely quartz, calcite, albite and microcline) were employed to construct bitumen-mineral interface systems. These models were validated by the experimental results and MD simulations reported in the literature. The hardening mechanism of the aged bitumen was analysed by comparing the density, cohesive energy density and fraction of free volume between the virgin and oxidised bitumen. Work of adhesion was computed to quantify the adhesive bonding property of the bitumen-mineral interface systems for the virgin, lightly oxidised and heavily oxidised bitumen models under dry and wet conditions. Results show that the oxidised products (carbonyl and sulfoxide) strengthen the intermolecular bonding, resulting in molecular

This study develops a damage mechanics-based crack growth model to predict crack length in a typical viscoelastic material (i.e., bitumen) under a rotational shear fatigue load. This crack growth model was derived using torque and dissipated strain energy equilibrium principles. The crack length was predicted using bitumen's shear moduli and phase angles in the undamaged and damaged conditions, measured by linear amplitude sweep (LAS) tests and time sweep (TS) tests, respectively. The two tests were both performed using Dynamic Shear Rheometer (DSR), thus the crack growth model was named as a DSR-C model. To validate the DSR-C model, the crack lengths after the TS tests were measured using digital visualisation of cracking surfaces for one virgin bitumen and one polymer-modified bitumen at two temperatures (15, 20 °C), two frequencies (10, 20 Hz) and two strain levels (5%, 7%) under unaged and aged conditions. Results show that the DSR-C model can accurately predict the crack length in the viscoelastic bitumen under the rotational shear fatigue load at different loading and material conditions. The crack growth includes initial transition period, steady growth period and rapid growth period under a controlled strain loading mode. The degradation of the material property results from the crack growth that initiates from the outer edge toward the centre of the sample under the rotational shear load.

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