Role of thermodynamic relaxation on effectiveness of recycling agents on properties of aged bitumen

Role of thermodynamic relaxation on effectiveness of recycling agents on properties of aged bitumen

Ren, S. (TU Delft Pavement Engineering)
Liu, X. (TU Delft Pavement Engineering)
Erkens, S. (TU Delft Pavement Engineering)

2024

The low-temperature relaxation and fatigue cracking performance are two essential aspects in estimating the rejuvenation efficiency of recycling agents (RAs). This study aims to fundamentally investigate the effects of recycling agent type/dosage and aging degree of bitumen on thermodynamic and rheological properties of rejuvenated bitumen at low and intermediate temperatures. Molecular dynamics (MD) simulations are utilized to predict thermodynamic indices of rejuvenated bitumen, further linked to critical low-temperature and fatigue indicators from experiments. The results reveal that all RAs show a regeneration effect on fractional free volume (FFV), self-diffusion coefficient (DS), glass transition temperature (Tg), and surface free energy (γ). Bio-oil and engine-oil exhibit higher rejuvenation efficiency on these thermodynamic properties than naphthenic-oil and aromatic-oil. The aging degree of bitumen and temperature show significant effects on rejuvenation efficiency. It is recommended to use the FFV parameter to predict the relaxation properties of rejuvenated bitumen. However, these thermodynamic indicators inadequately differentiate between rejuvenators and softeners. Based on crossover parameter results, most recycling agents (bio-oil, engine oil, and naphthenic oil) in this study display softening characteristics. Only aromatic oil effectively rejuvenates the crossover modulus (Gc) of aged binder. Notably, engine oil demonstrates the least rejuvenation in crossover parameters for the recovery of aged bitumen. Further, γ demonstrates a strong association with both Glover-Rowe (G-R) and fatigue crack width C500 indices across all cases involving rejuvenated bitumen. This work will build a multi-scale evaluation framework on the rejuvenation effectiveness of recycling agents on low-temperature and fatigue performance of aged bitumen.

Rejuvenated bitumen
Molecular dynamic simulation
Low-temperature performance
Thermodynamic indicator
Multi-scale connection

http://resolver.tudelft.nl/uuid:4ac82791-3ebc-42f0-9bf7-7d4ba888242d

https://doi.org/10.1016/j.fuel.2024.131658

0016-2361

Fuel: the science and technology of fuel and energy, 368

Institutional Repository

journal article

© 2024 S. Ren, X. Liu, S. Erkens