Preparation And Properties Of Montmorillonite/SBS Modified Bitumen Composites

SBS modified asphalt has been used more and more widely for the excellent performance. Unfortunately, SBS tends to degrade by exposure to heat, oxygen and UV light since SBS contains an unsaturated bond, which may make a contribution to the deterioration of bitumen pavement. Therefore, it is very important for the service life to improve the ageing resistance of SBS modified bitumen.Montmorillonite/styrene-butadiene-styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of Sodium montmorillonite (Na-MMT) and organophilic montmorillonite (OMMT). Effect of montmorillonite (MMT) on physical properties, rheological properties and ageing properties of SBS modified bitumen was investigated. The structures of MMT/SBS modified bitumen composites were characterized by XRD and fluorescence microscopy.The XRD results show that Na-MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. The addition of MMT increases the softening point and decreases the penetration of SBS modified bitumen. The high-temperature storage stability can also be improved by MMT with a proper amount added. Compared to SBS modified bitumen, MMT/SBS modified bitumen composites exhibit higher complex modulus, lower phase angle at the same temperature and show better rutting resistance at the same temperature.The ageing properties of MMT/SBS modified bitumens composites are ecaluated by the Rolling Thin Film Oven Test (RTFOT), the pressure ageing vessel (PAV) and long-term thermal oxidative ageing. The results show that the addition of MMT decreases both the viscosity aging index and the changes in softening point and increases the retained ductility. MMT/SBS modified bitumen composites show better resistance to ageing than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen and the degradation of SBS.Compared with Na-MMT, OMMT had greater effects in improving properties of SBS modified bitumen, which indicated that exfoliated structure was more effective than intercalated structure in enhancing properties of SBS modified bitumen.