Rheological and chemical evaluation on the ageing properties of SBS polymer modified bitumen: From the laboratory to the field

• Applied RCAT ageing produces more asphaltenes than the field ageing.
• Viscosity of SBS PMB decreases after the applied short-term ageing due to the degradation of SBS.
• Both rheological and chemical properties of bitumen are needed to link the lab to the practice.

This study investigated the ageing properties of the styrene–butadiene–styrene polymer modified bitumen (SBS PMB) from the laboratory to the field. The virgin SBS PMB had been kept for 23 years and its field-aged binder was extracted from the reclaimed stone matrix asphalt (SMA) after the 22-year service time. The rotating cylinder ageing test (RCAT) was performed to simulate the short term (STA) and the long term ageing (LTA) of the virgin binder in the laboratory; dynamic shear rheometer (DSR) was used to characterise viscosity and dynamic response of virgin and aged binders; Gel Permeation Chromatography (GPC) was adopted to analyse the molecular weight distribution of all binders. Results indicate that: (a) the 22-year field-aged binder had a higher viscosity than the 9-day lab-aged binder; (b) the field-aged binder had a similar dynamic response with the 5-day lab-aged binder; (c) the GPC result indicated applied lab ageing produced more asphaltenes than the field ageing. In general, the field ageing is very complicated and hardly mimicked by the lab ageing. Both rheological and chemical parameters of bitumen are needed to elaborate the relation between the ageing in the laboratory and in practice.