Multiscale Prediction of Viscoelastic Properties of Asphalt Concrete

The low viscosity of asphalt concrete at T>135 degrees C is necessary for the construction and compaction process of high-quality asphalt concrete layers. Whereas the continuous increase of viscosity with decreasing temperature is desirable for the reduction of permanent deformations during warm periods, so-called top-down cracking may occur in the course of temperature drops during cold periods. In order to explain the complex viscoelastic properties of asphalt concrete, a multiscale model is proposed. Hereby, the viscoelastic behavior of bitumen serves as input and the effect of air voids and aggregates is investigated. The viscous properties of bitumen are identified, using the bending-beam rheometer and the dynamic-shear rheometer, providing access to the viscoelastic material response for different temperature and loading regimes. With the rheological properties of bitumen at hand, the viscoelastic properties of mastic, mortar, and asphalt concrete are determined using continuum micromechanics, employing the elastic-viscoelastic "correspondence principle." The creep properties of asphalt concrete obtained from the presented mode of upscaling from the bitumen to the asphalt scale is validated by means of cyclic tests and static uniaxial creep tests.