Compressive Creep Behaviour of Asphalt Mixtures

The uniaxial and triaxial steady-state deformation behaviour of a gap graded and a continuously graded asphaltic mixture have been studied. Uniaxial creep and constant strain rate tests have been conducted over a range of stress levels, strain rates and temperatures, and triaxial creep tests have been conducted over a range of deviatoric stress levels and confining pressures. The steady-state deformation behaviour of both mixtures is found to be well captured by the Modified Cross Model which predicts linear viscous behaviour at low stress levels and non-linear viscous behaviour at high stress levels. The temperature dependency of the steady-state deformation behaviour is found to be well captured by the WLF equation. It is found that confinement has a stiffening effect on the steady-state deformation behaviour which is found to be higher for the continuously graded mixture. The volumetric strain is found to increase linearly with the shear strain with a gradient that is independent of stress level and confining pressure.