Simulation of Asphalt Concrete Plastic Deformation Behavior

Abstract

This paper presents discrete element method (DEM) simulation results of the plastic deformation behavior of asphalt concrete(AC) subjected to the loading of the asphalt mixture performance test. This consists of a repetitive vertical axial stress of 69 kPa for .1 s followed by a rest period of .9 s. Nine ACs were considered; three mix designs and three aggregate types. A single PG 76-22 modified binder was used for all nine mixes. Their microstructure was captured by X-ray tomography and the images processed were input into a DEM software package. The viscoelastic properties of the asphalt mastics were obtained by fitting Burgers models on frequency sweep dynamic shear rheometer data. These models were used to define viscoelastic contact laws for the mastics. These mastic contacts were assumed broken (i.e., the elastic constants of the Burgers models were set to zero) where the limits in linear viscoelastic behavior were exceeded. Flow number (FN) values were obtained by fitting the Francken model to the computed plastic deformation estimates. The results compared favorably to laboratory rutting measurements obtained on the same cores with the Hamburg wheel testing device (HWTD). The plastic strain at FN and the plastic strain rate at FN exhibited higher correlation with the HWTD rutting measurements than the FN values.