<p>A preliminary study suggested the potential of ferric chloride as a Lewis acid in recycling aged paving asphalts through deagglomeration of asphaltenes and reaction with oxidation species. Considering its strong coordination tendency towards conjugated aromatic rings and heteroatom-containing groups (carbonyls and sulfoxides) in aged binders, the present study is limited to two unaged neat and SBS (styrene–butadiene–styrene) polymer-modified asphalts. A multiscale methodology was adopted to evaluate the rheological and physicochemical changes as induced by ferric chloride, and also their interrelationships as interpreted by colloidal and Lewis acid–base principles. Ferric chloride enhanced stiffness and elasticity and improved rutting resistance in both binders, but diminished their fatigue and low-temperature performance. In the SBS binder, the shift of phase angle mastercurve toward Newtonian behavior indicated polymer network breakdown. Physicochemical analyses suggested that ferric ions likely formed coordination complexes with asphaltenes leading to their deagglomeration, and potentially broke large molecules into smaller ones, corresponding to a simultaneous increase of light fractions. The increased surface roughness was consistent with formation of these complexes, while the swollen butadiene segments in the SBS binder may have mitigated this roughness elevation. Ferric chloride also fragmented SBS molecules, as evidenced by the sharp morphological transitions in fluorescence microscopy and by the reduced average molecular weight of the polymer fraction in chromatography analysis. Infrared analysis indicated that the double bonds in the polybutadiene (PB) blocks were negligibly affected, leading to the inference that chain scission may have occurred at the allylic positions. These findings are expected to serve a solid foundation for further investigation into the use of ferric chloride in recycling aged asphalts, both independently and in combination with traditional regenerators/softeners.</p>