Effect of expanded vermiculite on microstructures and aging properties of styrene–butadiene–styrene copolymer modified bitumen

Organic expanded vermiculites (OEVMTs) were prepared using cetyltrimethyl ammonium bromide (CTAB) and octadecyl dimethyl benzyl ammonium chloride (ODBA) as intercalation agents. Effect of EVMT organic modification on physical and aging properties of styrene–butadiene–styrene (SBS) modified bitumen was investigated. The microstructures of the binders were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. EVMT/SBS modified bitumen forms a phase-separated structure, while OEVMT/SBS modified bitumens form the exfoliated nanostructures according to XRD analysis. OEVMTs show the more obvious influence on physical properties of SBS modified bitumen in comparison with EVMT. The compatibility between the EVMT and SBS modified bitumen is also improved after organic modification of EVMT. AFM analysis indicates that the contrast between the dispersed phase and the matrix phase in SBS modified bitumen increases with the addition of ODBA-EVMT. As a result of thin film oven test (TFOT), the viscosity aging index of SBS modified bitumen decreases, while the retained ductility and penetration increase obviously with the introduction of EVMT and OEVMTs. ODBA-EVMT/SBS modified bitumen has more pronounced improvements in aging resistance of SBS modified bitumen in comparison with CTAB-EVMT/SBS modified bitumen by preventing the phase-separated trend of the SBS modified bitumen during TFOT.

► EVMT/SBS modified bitumen forms the phase-separated structures.
► OEVMT/SBS modified bitumens form the exfoliated nanostructures.
► OEVMTs improve the high temperature stability and physical properties of the binders.
► OEVMT/SBS modified bitumens show the more pronounced aging resistance compared with EVMT.