Road paving without fossil sources - the future of bitumen.

This doctoral thesis addresses the challenge of reducing dependence on fossil fuels in the road infrastructure sector through the development of bio-binders. The research is framed within the broader transition toward renewable and circular materials and focuses on evaluating the performances obtained from different biological sources. The study initially outlines the production processes of conventional bitumen and the associated environmental impacts, subsequently introducing bio-based alternatives as viable technical and ecological solutions. An overview of binder categories based on the degree of fossil substitution is provided, including modified, fluxed, extended, and fully alternative binders. The main renewable feedstocks investigated include waste vegetable oils, lignin, agricultural residues, lignocellulosic biomass, algae, and animal fats. The experimental work is structured around three formulation strategies aimed at replicating the mechanical and functional behaviour of conventional bitumen using low-impact bio-based materials. These include: (1) a colloidal approach, focused on reconstructing the viscoelastic structure of bitumen through bio-derived components capable of mimicking the balance of S.A.R.A. fractions; (2) a chemical approach, based on cross-linking reactions involving bio-based oils and natural resins to form cohesive polymeric networks; and (3) a thermochemical approach, employing bio-crudes obtained from biomass conversion processes such as pyrolysis and HTL to develop binders with a reduced or null fossil content. The developed bio-binders were subjected to an extensive characterisation programme, including advanced rheological testing using a DSR, spectroscopic (FT-IR), thermal (TGA, DSC, and cone calorimetry), morphological, and adhesion/cohesion analyses. These investigations enabled a comprehensive evaluation of the thermo-mechanical behaviour, stability, and compatibility of the bio-based formulations. Overall, the results demonstrate that the proposed bio-binders can achieve rheological performance comparable to, and in some cases superior to, conventional petroleum-derived bitumen. The study confirms the potential of bio-binders as effective and sustainable alternatives, contributing to the decarbonization and increased circularity of road infrastructure materials.