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AFM Materials Journal Club

Nanoscale Viscoelastic Characterization of Asphalt Binders Using the AFM-nDMA Test

by M. F. Aljarrah and E. Masad

Mater Struct, 53, 110 (2020)

DOI: 10.1617/s11527-020-01543-3

The viscoelastic behavior of bitumen (asphalt binder) is the subject of one of the world’s longest running experiments: the famous University of Queensland pitch drop experiment started in 1927. This experiment is sensitive to the bulk properties of the material, but provides no information regarding the nanostructure of the material or viscoelastic properties at the nanoscale. Other more recent experiments with Dynamic Shear Rheometer (DSR) are similarly limited.

Aljarrah et al. have now applied PeakForce QNM and AFM-nDMA to investigate the mechanical properties of bitumen at the nanoscale, with the PeakForce QNM maps allowing identification of three phases (bee structure, interstitial, and matrix) and AFM-nDMA providing co-located viscoelastic spectra. By collecting these spectra at different temperatures the team was able to construct nanoscale master curves that could then be compared to bulk DSR measurements. They found that the DSR and AFM-nDMA curves were qualitatively similar, but that the nanoscale moduli were significantly stiffer and less viscous than the bulk. The authors attribute this difference to the molecular structure of the material probed by the AFM tip as compared to the bulk and to weaknesses at the interfaces between phases in the bulk.



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SUBJECT(S):

  • The nanoscale viscoelastic properties of asphalt binders
  • Atomic Force Microscopy-Nanoscale Dynamic Mechanical Analysis (AFM-nDMA) testing mode for nanoscale viscoelastic characterization of asphalt binders, esp. in contrast with traditional asphalt rheology
  • Testing guidelines and procedures for future experimental investigations


FEATURED BRUKER TECHNOLOGY:


KEY FINDINGS:

  • The shapes of the master modulus and phase angle curves obtained from the nano and bulk measurements are notably different
  • The nanoscale moduli were significantly stiffer and less viscous than the bulk


KEY TERMS:

AFM-nDMA, Asphalt Binder, Asphalt Rheology, Building Materials, Binder Properties, Construction Engineering, Viscoelastic Properties