Impact of Waste-HydroChar on the Rheological Behavior, Physical Properties, and Aging Resistance of Bitumen

In line with circular principles and the reuse of waste products, this study investigates the use of a waste-derived additive sourced from civil waste to modify the rheological and physical properties, as well as the aging resistance, of bitumen. Different dosages of waste-hydrochar (HC), produced via hydrothermal carbonization of digested sewage sludge, specifically 2%, 4%, and 10% by weight, were introduced to the bitumen, and the materials were characterized in terms of their rheological, physical, and aging behavior. Two aging protocols, e.g., short-term thermal aging and UV irradiation aging, were followed to evaluate the aging resistance of the bitumen with and without waste-hydrochar. The results obtained suggest that bitumen containing waste-hydrochar exhibits similar rheological and physical properties to bitumen without an additive, indicating the potential for using this waste material as a suitable bitumen additive. Furthermore, the presence of waste-hydrochar does not reduce the short-term thermal or UV irradiation resistance of bitumen, again suggesting the potential for using this waste material as a suitable bitumen additive. Finally, the results obtained have been compared with those of bitumen containing high-cost biochar, highlighting the potential to replace high-cost biochar with low-cost, waste-hydrochar.