Bitumen improvement with bio-oil and natural or organomodified montmorillonite: Structure, rheology, and adhesion of composite asphalt binders

•Bio-oil partly dissolves in bitumen, improving adhesion without worsening fluidity.•Hydrophobic clay exfoliates to nanosized particles in bitumen, unlike hydrophilic one.•Hydrophilic clay weakly changes the melt rheology but worsens elasticity upon cooling.•Hydrophobic clay causes bitumen gelling with increasing stiffness and yield stress.•Hydrophobic clay more effectively increases the bitumen cohesion and adhesion.