Evaluation of the long-term performance of naphthenic recycling agent in restoring the properties of aged bitumen

Investigating the performance of bitumen restored by recycling agents in maintaining or destroying the properties and characteristics of bitumen in the next period of pavement service is completely limited. The aim of this research was to evaluate the immediate and long-term effect of a naphthenic recycling agent in restoring the properties of aged bitumen. In this research, bitumen separation and infrared spectroscopy experiments to investigate the chemical properties of bitumen samples, Penetration, Softening Point, Rotational Viscometer, Multiple Stress Creep Recovery and Linear Amplitude Sweep were used to evaluate the physical and rheological properties of bitumen samples. To evaluate the long-term performance of the recycling agent, the restored bitumen was to long-term aged by aging simulation test. The results show that the use of naphthenic recycling agent in the optimal amount has restored the chemical, physical and rheological properties of aged bitumen to the base bitumen level. The naphthenic recycling agent results in a 38% reduction in the CI of aged bitumen, which indicates that the aged bitumen is softer and its colloidal structure is stable. It also reduces the rutting resistance of aged bitumen to the level of base bitumen. The limited increase in CI due to aging in restored bitumen indicates that the naphthenic recycling agent has performed well in maintaining the stability of the colloidal structure of bitumen in the long term. The results also show that the use of naphthenic recycling agent improves the fatigue performance of restored bitumen in the long term compared to base bitumen.