When it comes to describe the mechanical behaviour of hot mix asphalt (HMA), the change of the mechanical properties over time due to environmental impacts known as ageing has to be considered. Hardening and embrittlement of bitumen lead to a reduced resistance against cryogenic cracks and premature formation of fatigue cracks in bituminous layers. Within this work, the microstructure of bitumen is investigated by conducting static shear creep tests on artificially composed bitumen with asphaltene contents varying between 0 vol-% and 26.71 vol-% as well as on a paving grade bitumen 70/100. Both are considered in unaged and laboratory-aged (rolling thin-film oven test + pressure ageing vessel) conditions to be able to identify and describe ageing effects. While the properties of the considered material phases of bitumen (identical to saturates, aromatics, resins and asphaltenes (SARA) fractions) seem to remain unaffected, an increase of the asphaltene content due to ageing can be observed. A micromechanical model is proposed that allows a prediction of the consequences of these microstructural changes on the mechanical behaviour of bitumen. Atomic force microscopy and environmental scanning electron microscopy images confirm a composition consisting of a micelle-like structure in a contiguous matrix, a structural representative volume element concept based on SARA fractions is suggested, extending an existing multiscale model for HMA. A very good accordance between model predictions and experimental results indicates the model's ability to reproduce as well as to describe the effects related to ageing.

Pavement design in Austria is currently based on a catalogue of standard constructions distinguishing seven load classes and eight pavement types, which can be chosen depending on the traffic-related parameters AADT (annual average of the daily traffic for each vehicle type i) or AADTT (annual average of the overall daily truck traffic). This approach does not allow one to take performance-related material characteristics or detailed traffic load information into account. To resolve these limitations, a mechanistic approach for the design of bituminous pavements in Austria was developed. Thereby, design levels for the important parameters traffic load as well as hot mix asphalt stiffness and fatigue behaviour are introduced accounting for the level of detail of these variables. This approach ensures that necessary design reserves decrease with increasing experimental effort related to the parameter identification. Hence, this method provides modern, performance-based and economic pavement design.

The investigation of the pavement performance under dynamically increased wheel loads combines approaches about the modelling of axle assemblies, the simulation of the dynamic wheel loads due to longitudinal unevenness as well as the estimation of the impact on the service life of pavements. The focus in this work is laid on the determination of distress and service life of rigid pavements under dynamic wheel loads using a recently introduced and for the purpose of this study adopted mechanistic-empirical design method for rigid pavements. The results show a good correlation between the assessed Weighted Longitudinal Profile (WLP) (as an indicator for longitudinal unevenness) and the theoretical service life of rigid pavements. Based on that correlation a rating scheme for longitudinal unevenness is introduced. It allows the classification of the unevennes of roads in a five-grade system depending on the WLP and the definition of limiting values for the longitudinal unevenness.