A contribution to the modeling of permanent deformations of bituminous mixes

Abstract

Rutting is one of the well-recognized road surface distresses in asphalt concrete pavements that can affect the pavement service life and traffic safety. The rutting phenomenon is linked with the permanent deformation accumulated after each cyclic loading due to the traffic. It is rather badly described by the traditional pavement analysis method. No rational approach is proposed to model this effect. A new test was developed at the “Département Génie Civil et Bâtiment” (DGCB) of the “Ecole Nationale des Travaux Publics de l’Etat” (ENTPE) to study permanent deformation of bituminous mixes. Experimental tests were carried out in order to contribute with the comprehension of the phenomena and the formulation of a law adapted for the rutting phenomenon modeling.A thermo-viscoplastic law has been developed at the DGCB for bituminous mixes during the last decade. This law introduces various experimental observations: general linear viscoelastic behaviour in the small strain range, non-linearity and viscoplastic flow. The aim of this paper is to widen the scope of this law by introducing permanent deformation in his formalism. Comparisons between the experimental value and the computed value of the slope of the secondary stage are presented for three temperatures (15°C, 25°C and 35°C), two frequencies (1Hz and 10Hz), and five stress amplitudes (0.1MPa, 0.2MPa and 0.3MPa in compression and –0.05 and –0.1MPa in extension).