Pyrolysis Bio-Oil as a Partial Substitute for Conventional Bitumen in More Sustainable Asphalt Mixtures

The use of bio-binders has sparked increasing interest in the production of bituminous mixtures for road pavements. For this reason, this article evaluates the effect of partially replacing two conventional 35/50 and 50/70 penetration-grade bitumens with bio-oil obtained from the pyrolysis of biomass. In the first stage, the bio-oil was subjected to thermal pre-treatment combined with agitation and conditioned at different temperatures and stirring speeds for different durations to progressively reduce the mass loss measured under thermogravimetric test conditions and achieve a homogeneous mixture with the base binder. Based on this pre-treatment, thirteen bio-binder formulations were initially evaluated using 35/50 bitumen and varying the bio-oil content to assess the properties of the bio-binders before and after short-term ageing. Subsequently, a gap-graded bituminous mixture, type BBTM 11B, was produced using the bio-binders, and the volumetric and mechanical properties were analysed to identify the bio-binder exhibiting the most suitable performance. Finally, the selected 10% bio-oil replacement level was evaluated using 50/70 bitumen. The results confirmed that the selected formulation satisfied the specific laboratory acceptance criteria evaluated for BBTM 11B mixtures.