A thermo-viscoplastic model for bituminous materials

This paper introduces the 3D formalism of the DBN (Di Benedetto, Neifar) model developed at ENTPE (Ecole Nationale de Travaux Publics de l’Etat). This model is an attempt to describe with a unique formalism the different types of behavior observed for bituminous materials. The DBN model is very versatile. The proposed formulation can be simplified or adapted following the required property to be introduced. The law can then be very simple and easy to use (linear viscoelastic or even elastic) or more complicated (introduction of non linearity, permanent deformation or fatigue). Considering the thermo-sensitivity of bituminous materials, the temperature influence is always considered.

The presented developments focus on the modeling of linear behavior, which is observed for bituminous mixes in the small strain domain (i.e. strain amplitudes less than some 10

-5

m/m). The non linear behavior up to failure, which can be ductile or brittle, the rutting and the fatigue phenomena are only evoked due to the lack of space. These phenomena have been treated in others publications. In this paper, the three-dimensional (3D) linear viscoelastic (LVE) behavior is investigated. Complex Poisson’s ratio (v*) is measured and introduced. Its evolution with temperature and frequency is studied for different bituminous materials. Experimental results show that the Time Temperature Superposition Principle is applicable in the 3D case. The same shift factor applies for E* and v*. Comparisons between simulations in the linear and non-linear domains and experimental data are proposed. Thermal Stress Restrained Specimen Tests (TSRST) which introduce thermo-mechanical coupling are also simulated.