Evolution of asphalt binder microstructure due to tensile loading determined using AFM and image analysis techniques

Abstract

In this study atomic force microscopy (AFM) creep indentations were performed to extract viscoelastic properties of the different domains (defined as microrheology) observed in bitumen samples from two different sources. The microrheology and geometry obtained using the AFM were used to perform finite element (FE) simulations to study the effect of bitumen microstructure on internal stress distribution. FE analyses suggest that microstructures with varying mechanical properties cause localised stress amplification that can lead to cracking/phase separation. A custom-made loading frame in conjunction with an AFM was used to examine the effects of tensile strain on bitumen microstructure. FE simulation and experimental results show that applying strain resulted in damage/phase separation concentrated in the interstitial zone between neighbouring bee structures, defined as load-induced phase separation. This study suggests that evaluating the bitumen microstructure and microrheology is critical to understanding the mechanisms of damage evolution in bitumen and engineering binders with higher inherent durability.

Keywords::

• asphalt
• AFM
• microrheology
• microstructure
• load induced phase separation
• image analysis
• micro scale response
• finite element analysis

Additional information

Funding

This work is part of the research being undertaken by the Asphalt Research Consortium (ARC) and is funded by the Federal Highway Administration (FHWA). The authors would also like to acknowledge NSF [grant number CMMI-1053925] for partially supporting this study.