NMR Self-Diffusion and Transverse Relaxation Time in Bitumen: The Effect of Aging.

Area of Science:

• Materials Science and Engineering
• Physical Chemistry

Background:

• Bitumen aging alters its rheological and molecular properties.
• Understanding molecular dynamics is crucial for predicting bitumen performance.

Purpose of the Study:

• To investigate the molecular dynamics of two bitumen types under various aging conditions.
• To correlate aging effects with changes in self-diffusion and relaxation times.

Main Methods:

• Dynamic Shear Rheometry (DSR) for rheological properties.
• Nuclear Magnetic Resonance (NMR) techniques including Pulsed Field Gradient Stimulated-Echo (PFGSE) and relaxometry (CPMG).
• Artificial aging protocols (short- and long-term).

Main Results:

• Gel-sol transition temperature increases with aging time.
• Unexpected correlation between bitumen viscosity Arrhenius parameters and those of simple liquids.
• Broad distributions of self-diffusion coefficients (D) and continuous unimodal distributions of transverse relaxation times (T2) were observed and characterized.

Conclusions:

• Aging significantly impacts bitumen molecular dynamics.
• Bitumen systems share fundamental molecular processes with simple liquids.
• NMR provides valuable insights into the aging mechanisms of bitumen.