Valorization of C. Linum HTL By-Products as Renewable Modifiers for Sustainable Bituminous Binders

This study explores the direct application of hydrothermal liquefaction (HTL) by-products derived from the macroalga C. linum in a 35/50 penetration grade bitumen. The hydrophobic HTL bio-oil and the solid hydrochar fraction were incorporated individually and jointly to evaluate their influence on the rheological behavior of the binder. Dynamic shear rheometer (DSR) tests were conducted to assess complex modulus and phase angle variations across temperature and frequency ranges. The results indicate that HTL bio-oil acts as a plasticizing agent, reducing stiffness and increasing viscous response, whereas hydrochar contributes to elastic reinforcement. The combination of both fractions produced a balanced viscoelastic profile, maintaining good mechanical stability while improving flexibility. These findings demonstrate the potential of C. linum HTL products as renewable modifiers for bituminous binders, supporting the valorization of a problematic biomass waste into sustainable pavement materials.