Nonlinear viscoelastic analysis of asphalt cement and asphalt mastics

The nonlinear viscoelastic (NLVE) behaviour of asphalt cement and asphalt mastic are studied using temperature and frequency sweep tests and repeated stress sweep cyclic load tests. These experiments show that the response functions of these materials are strain-level dependent. The experiments also show that NLVE occurs simultaneously with other mechanisms, which complicates isolation and subsequent characterisation. For the asphalt mastics studied, the NLVE is found to relate to only the influences of the asphalt cement. Based on these experiments and analyses, a thermodynamics-based constitutive equation is proposed. The proposed model is chosen based on the hypothesis that the observed NLVE is strain related, which is different from other similar models and agrees with existing frameworks for evaluating damage. The resulting model is found to capably predict the stress-strain behaviour of asphalt cement and asphalt mastics at different volumetric concentrations of filler under cyclic and constant rate loading.