Study of the inter-diffusion characteristics and cracking resistance of virgin-aged asphalt binders using molecular dynamics simulation
BY Cui and H Wang and XY Gu and DL Hu, CONSTRUCTION AND BUILDING MATERIALS, 351, 128968 (2022).
To investigate the inter-diffusion characteristics and cracking resistance of blended asphalt binders, the virgin -aged asphalt models were developed through the molecular dynamics (MD) simulation. Based on the mass density profiles of virgin and aged asphalt binders, the effect of temperature on the inter-diffusion coefficients was analyzed. According to the spatial distribution of atoms, different blending states including partial blending and total blending were distinguished. The cracking resistance of blended asphalt binders was characterized by the fracture energy obtained from the stress-displacement responses. Relationship between degree of blending and cracking resistance was explored. Results show that high temperatures can increase the inter- diffusion co-efficients of virgin and aged asphalt binders by enhancing the intramolecular potential energy and Van der Waals (VdW) interaction energy. Compared to aged asphalt binder, the virgin asphalt binder may be more susceptible to temperature. Under tensile loading, the crack always initiates in the blending zone of partially blended asphalt binders. However, for the totally blended asphalt binder, the crack is more likely to occur at localized defect locations which is randomly distributed. The ability of blended asphalt binder to withstand deformations be-comes better, but the maximum tensile strength decreases a lot as the temperature increases. There is a positive correlation between the degree of blending and fracture energy of blended asphalt binders, indicating that the asphalt binder with a higher degree of blending has better cracking resistance. The results of MD simulations can help determine how much aged binder can be mobilized to blend with virgin binder and help select appropriate virgin binders or other additives that can improve the blending between virgin and aged asphalt.
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