The flow properties of bitumen in the presence of carbon dioxide

The present dissertation discusses the flow behaviour of bitumens in the presence of CO₂. Firstly, the viscoelastic behaviour of bitumen is studied and an appropriate constitutive equation is identified to describe its rheological behavior. The K-BKZ constitutive equation has been shown to represent accurately the rheological properties of bitumen. Analysis of experimental results revealed that either the Papanastasiou or the Marucci form of the damping function can be used in the K-BKZ constitutive equation. Moreover, the damping function was found to be independent of temperature (0°C-50°C). Secondly, the effects of temperature, pressure, dissolved carbon dioxide and shear rate on the rheological response of bitumen are investigated by using the reduced variable method at the temperature range of –10°C to 180°C and pressures up to 15 MPa. The double–log model is found to be the most accurate equation in describing the effect of temperature on the viscosity of bitumen over a wide range of temperature while the Barus model with the temperature–dependent parameter is found to be the most appropriate correlation to represent the effect of pressure. The Fujita–Kishimato equation, resulting from the free volume concept modelling, is employed to account for the effect of dissolved CO₂ on the viscosity of the bitumen–CO₂ mixture. The results show that the viscosity is influenced by the temperature and saturation pressure. Thirdly, the combined pressure-decay technique with rheometry is developed to measure the diffusivity of CO₂ in bitumen at the temperatures of 30˚C, 50˚C, 70˚C, 90˚C and 110˚C and saturation pressures of 2, 4 and 10 MPa. The impact of temperature on the diffusivity of CO₂-bitumen systems can be described by the Arrhenius equation. The diffusivity increases with pressure at gaseous CO₂ state. The increase is more dominant at lower temperatures while the diffusivity increase is 53% at 30˚C compared to 25% at 70˚C. It is shown that changing the state of CO₂ impacts the diffusivity values of in bitumen while the diffusivity is higher for the liquid CO₂ compared to supercritical CO₂. Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat