A framework for the analysis of damage and healing viscoelastic behaviour of asphalt binders

This paper aims to develop a framework for characterizing damage and healing viscoelastic behaviour of asphalt binders. The framework is based on modifying the 2S2P1D (two springs, two parabolic elements, and one dashpot) viscoelastic model such that the evolution of the exponent 'k' of the parabolic creep function is associated with damage and healing behaviours. The model efficacy is corroborated through the analysis of viscoelastic response, damage, and healing of four asphalt binders (i.e. one unmodified asphalt and three other asphalts modified using low-density polyethylene and various additives.) These binders were subjected to strain sweep tests to determine their linear viscoelastic strain limit. In addition, frequency sweep tests at several temperatures were conducted to obtain binder linear viscoelastic parameters. Then, the binders were subjected to strain-controlled, cyclic progressive damage tests (continuous loading) as well as cyclic damage-healing tests (i.e. cyclic loading with rest periods). The test data were analysed to obtain the storage and loss moduli as functions of loading cycles, and they were modelled using the modified version of the 2S2P1D model. The exponent of the parabolic creep element 'k' was formulated using a hyperbolic cosine function that quantifies the deviation from the linear viscoelastic response during damage and healing. The results showed that the 'k' function was suitable to quantify the damage and healing responses of the asphalt binders at the test conditions. Furthermore, the parameters in the 'k' hyperbolic cosine function were used to create a plot for classifying binders based on their damage and healing characteristics.