The purpose of this study was to characterize the micromechanical properties of
various structural components in asphalt using Atomic Force Microscopy (AFM). The
focus of the study was based on nano-indentation experiments performed within a
micro-grid of asphalt phases in order to determine micromechanical properties such as
stiffness, adhesion and elastic/plastic behavior. The change in microstructure and
micromechanical behavior due to oxidative aging of the asphalt was also a primary focus
of the study. The experiment was performed with careful consideration of AFM
artifacts, which can occur due to factors such as geometry of the cantilever tip,
hysteresis, filtering methods and acoustic vibrations. The materials used in this study
included asphalts AAB, AAD and ABD from the Materials Reference Library (MRL) of
the Strategic Highway Research Program (SHRP), chosen due to variations in crude
source, chemical composition and elemental analysis for each asphalt type.
The analysis of nano-indentation creep measurements corresponding to phase-separated
regions ultimately revealed heterogeneous domains in asphalt with different
mechanical properties, and oxidative aging was found to induce substantial microstructural change within these domains, including variations in phase structure,
phase properties and phase distribution. The form and extent of these changes, however,
were different for each asphalt studied. Data analysis and information collected during
this study were used for comparisons to existing models and asphalt data, which
validated results and established correlations to earlier, related studies. From these
comparisons, it was found that data parallels followed expected trends; furthermore,
analogous interpretations and distinctions were made between results from this study and
the micellar and microstructural models of asphalt. This study of micromechanical
properties that govern asphalt behavior has yielded information essential to the
advancement of hot mix asphalt (HMA) performance, including a new asphalt “weak
zone” hypothesis and a foundation of data for implementation into new and existing
asphalt models.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-12-8749 |
| Date | 2010 December 1900 |
| Creators | Allen, Robert Grover |
| Contributors | Little, Dallas N. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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