The identification of material phases at the so called bitumen-scale in context of multiscale modeling of asphalt is presented. For this purpose, atomic force microscopy (AFM), providing insight into the surface topography and mechanical properties, is applied to different types of bitumen. Based on the obtained AFM results, four different material phases at the bitumen-scale are identified. These phases are related to the chemical composition of bitumen, characterized by a wide range of molecular mass. Within the anticipated multi-scale model, the properties of these phases serve as input for upscaling, providing material parameter of the bitumen phase at the next-higher scale, i.e., the mastic-scale.

The low viscosity of asphalt concrete at T>135°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...