A model combining structure and properties of a 160/220 bituminous binder modified with polymer/clay nanocomposites. A rheological and morphological study

The present contribution focuses on the modification of a 160/220 bituminous binder with clay and polymer/clay nanocomposites. Bitumen/polymer/clay ternary blends were prepared using styrene–butadiene–styrene, ethylene vinyl acetate and ethylene methylacrylate copolymers mixed with an organomodified montmorillonite. Dynamic mechanical analyses were performed in the extended domain of stress, temperature and frequency to analyse the thermorheological behaviour of the blends. The time–temperature superposition principle was applied to shift the experimental data recorded at different temperatures and generate master curves of the linear viscoelastic functions. For all blends, the mechanical response of the system was found to be strongly and intimately influenced by the nanocomposite modification. In some cases, a solid-like behaviour appears and delays the Newtonian transition. Morphological analyses performed with fluorescence microscopy allowed to associate the binder properties with the presence of clay silicates, which alter the colloidal equilibrium of the bitumen and enhances the compatibility between bitumen and polymers. Based on the morphological and rheological results, a structural model of the prepared blends is proposed.