Analytical investigation of the impact of a novel bio-based recycling agent on the colloidal stability of aged bitumen

While many additives have been used to modify the properties of aged bituminous materials to ensure long-term durability in highly recycled pavements, consensus on the definition of rejuvenation and the associated mechanisms does not exist. Thus, further clarification and assessment of impacts on ageing and of various approaches to rejuvenation are imperative. The present study utilises chemical fractionation, differential scanning calorimetry, and atomic force microscopy to evaluate the impact of a chemically modified vegetable oil-based recycling agent in terms of bitumen colloidal stability and phase compatibility. The Colloidal Instability Index (CII) is shown to be a useful parameter for monitoring the effect of ageing on rejuvenated bitumen. The rejuvenator tested in this study showed good ageing stability as indicated by the relatively limited increase in CII due to ageing. Differential scanning calorimeter thermal analysis of the bitumen showed an improvement in the glass transition of aged bitumen through the use of rejuvenators. Extended Bending Beam Rheometer testing at isothermal conditions around the glass transition temperature showed that the rejuvenator effect is not affected by physical hardening. The results are used to support a proposed categorisation of the impact mechanisms of recycling agents.