Effect of reactive ethylene terpolymer modification on bitumen’s microstructure, rheology, and porous asphalt mix properties

ABSTRACT

The specific objective of this study was to investigate the effect of reactive ethylene terpolymer (RET) modification on bitumen properties at the nano and macro scales, as well as on porous asphalt (PA) mix properties. Measurements using the dynamic shear rheometer (DSR) and the bending beam rheometer (BBR) showed that RET modification of bitumen significantly improved the high-temperature properties, while intermediate- and low-temperature properties were similar to the base bitumen. The linear amplitude sweep (LAS) test conducted using the DSR showed that RET modification improved fatigue resistance. Consequently, chemical analysis and PeakForce^™ Quantitative Nano-Mechanical^™ (PF-QNM) atomic force microscopy (AFM) imaging were used to evaluate the microstructure and nanomechanical properties of the polymer modified bitumen (PMB) and the base bitumen before and after long-term ageing. The chemical analysis provided useful insights that complemented and helped to explain the AFM and rheology tests. The AFM results supported the LAS test findings in showing that RET modification improved the resistance of aged bitumens to cracking. The results of testing the PA mix showed significant improvements in moisture damage and ravelling resistance due to RET modification.

KEYWORDS:

• AFM
• PF-QNM
• PMB
• reactive ethylene polymer
• porous asphalt
• Elvaloy

Acknowledgements

The authors would like to thank Christian Gow (Coherent Scientific Pty Ltd Australia) for providing useful tips on AFM equipment operation and image analysis. A special thank you to Higgins New Zealand (especially Mr. Sean Bearsley) for providing the base bitumen and the facilities for bitumen characterisation as well as some test data on the base bitumen and PMB. Road Science New Zealand (especially Mr. Richard Carter) is much appreciated for providing facilities for asphalt mix preparation and testing. Thank you to C.J. DuBois (Dow Chemical) for providing samples of RET polymers, including ELVALOY™ 5160; guidance on the use of this polymer; and reaction sequences for EEGMA. Finally, the assistance of Dr. Y. Wubulikasimu in the AFM operation is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the author(s).