Evaluation of long-term effects of isothermal conditioning of binders recovered and stabilised from bitumen emulsion

Cold recycling technology is gaining popularity as an economically and environmentally beneficial alternative to Hot Mix Asphalt (HMA). The cohesion of cold recycling mixtures (CRMs) containing bitumen emulsion (BE) is provided by residual bitumen due to the emulsion breaking process at ambient temperatures. The influence of CRM and HMA production operations on the ageing behaviour of bituminous binders needs further investigation. In this study, the basic, rheological, and chemical properties of binders recovered and stabilised (STAB) from unmodified and SBS-modified cationic BEs were investigated and compared to the properties of the unaged and short-term aged (RTFOT) base binders. Dynamic Shear Rheometer (DSR) tests were performed to examine the impact of the recovery, stabilisation, and RTFOT ageing in the initial testing phase and after long-term isothermal conditioning, simulating base course conditions. To quantify these effects, the Ageing (AI) and Conditioning (CI) indexes were introduced, respectively. The results showed that in the initial testing stage, the STAB binders exhibited intermediate basic and rheological properties between unaged and RTFOT-aged ones. Yet, statistical analysis has proven that the applied long-term conditioning significantly influenced the dynamics of change in the complex shear modulus (G*) of STAB and RTFOT binders. FTIR spectroscopy results confirmed this observation.