On the use of linear viscoelastic constitutive relations to model asphalt

In this article, the appropriateness of modelling asphalt using linear viscoelastic constitutive relations is explored. Towards this, a rate-type nonlinear viscoelastic model recently proposed by Santoshreddy et al. (2011) is used and it is shown that the stress relaxation and creep response of asphalt are influenced by the type of experiment, initial rate of displacement (or loading) and the stress and strain measure used. Furthermore, it is shown that the creep and stress relaxation functions are not dependent functions as required by the linear viscoelastic theory, even in the range of values of engineering strain and stress in which the linearity property holds approximately. These observations lead one to conclude that linear viscoelastic models maybe inappropriate to model asphalt.