Micromechanical-analogical modelling of asphalt binder and asphalt mixture creep stiffness properties at low temperature

The Hirsch model and the ENTPE transformation are commonly used to predict low-temperature creep stiffness of asphalt binders from the corresponding asphalt mixture experimental data (forward problem) and vice versa (inverse problem). Nevertheless, the applicability of these models is affected by low accuracy and limited understanding of the model parameters, respectively. In addition, the transformation parameter, alpha, associated with the ENTPE equation, cannot be directly obtained without relying on both binder and mixture creep testing. This paper presents a comprehensive experimental and theoretical study to link model parameters and ENTPE transformation to the mixture microstructure. This is accomplished by three-point bending tests, performed on asphalt binders and mixtures, digital image processing and statistical evaluation of the mixture microstructure, together with a newly proposed micromechanical-analogical material model, called Moon Cannone Falchetto (MCF) model, used for deriving an explicit expression of the alpha parameter. The values of alpha obtained by fitting the Huet model to the asphalt binder and asphalt mixture laboratory results are compared with the values predicted by the newly proposed formulation based on microstructural and volumetric information. The results indicate that reasonable predictions of low-temperature creep stiffness of asphalt binder can be obtained from the corresponding mixture low-temperature creep properties when the new expression of alpha derived from the MCF model is used in the ENTPE transformation.