Rheology of bitumen: Effects of temperature, pressure, CO_2 concentration and shear rate

摘要

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 ℃ to 180 ℃ and pressures up to 15 MPa. A state of the art pressure cell set-up was utilized with a stress/strain controlled rheometer (Anton-Paar, MCR-501) to collect the experimental data on the Athabasca bitu-men-CO_2 mixture. 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. Excluding the effect of overhead pressure, the Fujita-Kishimato equation, resulting from the free volume concept modelling, is employed to account for the effect of dissolved CO_2 on the viscosity of the bitumen-CO_2 mixture more precisely. Moreover, a psuedoplastic model with a zero-shear viscosity is more rational to consider the effect of shear rate on the flow properties of the bituminous mixtures. The experimental conditions are carefully considered to avoid introducing flow instabilities into the mixture. It is demonstrated that the rheological properties of bitumen are more sensitive to the variables at lower temperatures.