Fatigue cracking is one of the primary modes of distress in asphalt pavements that has an
important economic impact. Fatigue resistance characterization of an asphalt mixture is a
complex issue due to: (i) composite nature of the material, (ii) gradation of aggregate
particles, (iii) variation of asphalt film thickness, (iv) air voids distributions, (v) asphalt
binder nonlinear viscoelastic behavior, (vi) effects of binder oxidative aging as a
function of time, and (vii) micro crack healing during rest periods. Different methods to
assess fatigue cracking in asphalt materials are available in the literature. However, there
is no methodology to characterize fatigue cracking behavior of asphalt materials that is
independent of the mode of loading (controlled-strain or controlled-stress). The objective
of this research is to develop a new methodology to characterize fatigue cracking of the
fine aggregate matrix (FAM) portion of asphalt mixtures using dynamic mechanical
analyses (DMA). This is accomplished through different, but related, approaches. The
first approach relies on identifying the various mechanisms of energy dissipation during
fatigue cracking that are manifested in: (i) nonlinear viscoelastic deformation, (ii)
fracture, and (iii) permanent deformation. Energy indices were derived to quantify each
of these energy dissipation mechanisms and to quantify fatigue cracking irrespective of
the mode of loading. The first outcome of the approach is a fatigue damage parameter
(crack growth index) that provides comparable results for a given material even when
tested under different modes of loading and different load (strain or stress) amplitudes. The developed fatigue characterization method has a lower coefficient of variation when
compared to conventional parameters (number of load cycles to failure or cumulative
dissipated energy). The crack growth index parameter was also qualitatively and
quantitatively compared to three dissipated energy methods available in the literature.
The second outcome of this research is a constitutive model that can describe both
asphalt mixtures’ nonlinear viscoelastic response and fatigue damage in one formulation.
Nonlinear viscoelastic as well as damage parameters were obtained for both modes of
loading. This second approach has the advantage that the constitutive model can be
implemented in a numerical framework to describe the response of asphalt mixtures
under various boundary conditions.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-3136 |
| Date | 15 May 2009 |
| Creators | Castelo Branco, Veronica Teixeira Franco |
| Contributors | Little, Dallas N. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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