Evaluation of Viscoelastic Properties and Cracking Behaviour of Asphalt Mixtures with Laboratory Aging

Aging can significantly affect the performance of asphalt mixtures causing increase in stiffness, reduction in relaxation capability and increase in brittleness. These changes can be quantified through viscoelastic properties and cracking behaviour of asphalt mixtures. In this study, six mixtures are evaluated using different laboratory conditioning protocols (loose mixture conditioned at various temperatures and durations to represent different aging levels) to evaluate how the viscoelastic, fatigue, and fracture properties of the mixtures will change over time. Comparison of viscoelastic characterization between different aging levels and mixtures is conducted by using complex modulus testing. Semi Circular Bending (SCB) and Disk Shaped Compact Tension (DCT) tests are used to evaluate the fracture behaviour of the mixtures. The Simplified Viscoelastic Continuum Damage (S-VECD) testing is used to estimate the ability of the mixtures to resist fatigue cracking. The results indicate that the viscoelastic, fatigue and fracture properties of the mixtures change significantly with aging. The two long term conditioning protocols induce statistically similar changes in linear viscoelastic properties and fatigue properties but produce differences in fracture indices. In this study, two virgin mixtures generally have better fracture and fatigue performance than the four mixtures with RAP. Two mixtures which have the largest difference between the high and low performance grade temperatures show the largest change in fracture and fatigue properties with aging.