As the main approach for improving the overall performance of asphalt pavements, the modification of base bituminous binders has been applied in asphalt pavement engineering for over 70 years. The need for such modification was prompted mainly due to the limitations of conventional asphalt binders produced from crude petroleum. The performance of asphalt mixtures is improved using various modifiers and additives such as elastomers and plastomers, chemical modifiers, extenders, oxidants and antioxidants, hydrocarbons, anti-stripping additives, and rejuvenators. Their interaction with base bitumen can be either physical or chemical, or even both, and potentially leads to a wide range of distinct rheological, physicochemical, micromechanical, microstructural, and other phenomena across all length scales. Furthermore, due to economic and environmental concerns, innovative modifiers and additives and recycled materials are continually being investigated and developed to find the most efficient and economical products for asphalt pavements.

Because of the enormous potential the above-mentioned modification approaches have for engineering and economic aspects of asphalt performance, a deep, materials science-based understanding of the intrinsic relations in the background of macroscopic behaviors is extremely important. Therefore, the engagement of cutting-edge experimental techniques in the domains of rheometry, viscometry, damage and fracture mechanics, microscopy, spectrometry, calorimetry, tomographic imaging, and image analysis are the prerequisite for obtaining new fundamental knowledge on the main interactions between modifier, bitumen, and the other components of the mixture. Such insights should enable us to influence, control, and as an ultimate objective adjust the overall behavior of modified bitumen in asphalt mixtures across all hierarchic levels (from binder, over mastic and mortar, to pavement layer) of these multiphase systems.

The aim of this Special Issue is to promote original research and review articles presenting experimental and analytical results on innovative modification concepts of bitumen from the perspective of individual phases as well as of entire asphalt and even pavement systems.

Potential topics include but are not limited to the following:

• Compound polymer modification of asphalt binder
• Unconventional fillers and nanomaterials in asphalt
• Alternative bituminous binders, such as bio-binders and reclaimed asphalt binders
• Mechanical performance of modified asphalt binders
• Durability of modified asphalt mixtures
• Mechanism and performance characterization of recycled asphalt materials
• Rheomechanics of bitumen-based fine aggregate matrix systems
• Physicochemical and mechanical aspects of rejuvenation