Modelling asphalt concrete viscoelasticity with damage and healing

The behaviour under load of asphalt concrete (AC) was viewed as additively separable into viscoelastic and viscoplastic components, and the study focused on modelling the pre-peak response of the viscoelastic part under constant temperature conditions. Non-linear viscoelastic behaviour was first exposed in several test modes, and a constitutive theory was subsequently offered – potentially capable of capturing and reproducing the observations. The modelling was based on replacing applied stresses in the linear convolution formulation with effective stresses; it included a mechanism for simulating the following effects: (i) short-lasting damage, (ii) long-lasting damage, (iii) stiffening under compressive conditions and (iv) healing during recovery intervals. As an initial validation effort, the model’s reproducibility was assessed by calibration to a uniaxial compression experiment consisting of both small and medium strain levels. Next, the calibrated model was employed to forecast small-strain behaviour in a standard complex modulus test. The simulated results qualitatively agree with recently reported findings that challenge the existence of a linear viscoelastic domain for AC.