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@PHDTHESIS{Fan:834563,
author = {Fan, Zepeng},
othercontributors = {Oeser, Markus and Wang, Linbing and Wang, Dawei},
title = {{M}ultiscale study of the bitumen-aggregate interfacial
behavior based on molecular dynamics simulation and
micromechanics},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2021-09995},
pages = {1 Online-Ressource : Illustrationen},
year = {2021},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2021},
abstract = {The bitumen-aggregate interfacial phenomena are an area
where chemistry, physics, and engineering intersect. While
continuous research efforts have been devoted to this issue
in the past decades, much less is known about the
fundamental mechanisms controlling the origins and the
evolution of interfacial failure. The complexity lies in the
multifactorial and multiscale nature of bitumen-aggregate
interfacial behavior. The interaction between bitumen and
aggregate relies directly on an intricate interplay of
bitumen chemistry, aggregate mineralogy, and surface
topography; and the interfacial performances in service are
also closely related to the random heterogeneous
microstructure of asphalt mixture, the periodical climate
conditions, and the repeated vehicle loads. Moreover, the
heterogeneity of the interacting components ranges across
nine orders of magnitude in length scales. The current
thesis is dedicated to developing a “bottom-up” approach
which handles the enormous number of factors across the
micro-to-macro length and time scales. A mechanistic study
using molecular dynamics simulation was carried out to
uncover the adsorption configuration of bitumen-aggregate
interface at the molecular scale and how the aggregate
mineralogy affects it. The microstructural of the adsorbed
bitumen layer was found to be a superposition of two
configurations: the layered configuration in the
near-surface region arising from aggregation and parallel
orientation of the bitumen molecules, and the gradient
descent configuration in the region further away from the
surface. The degree of concentration and radius of influence
are significantly impacted by the mineral surface. The
hypothesis of selective adsorption was tested by probing the
distribution characteristics of different fractions in
bitumen, and the results suggest a rejection of the
hypothesis.For purpose of investigating the water-induced
damage between bitumen and aggregate, the rolling bottle
tests were conducted for six kinds of aggregates, and the
ternary bitumen-water-aggregate interface models were
established to perform molecular dynamics simulations. The
results indicate the existence of competitive adsorption
between bitumen and water molecules at the mineral surface,
and the penetration capacity of bitumen molecule is greatly
affected by the mineral property. Aggregates with higher
content of nepheline, chlorite, pyroxene and olivine
minerals are more likely to exhibit better moisture damage
resistance while aggregates with higher content of quartz,
plagioclase, and calcite minerals do the opposite. The
influence of surface topography on the adhesion and
water-induced debonding behaviors of bitumen on aggregate
surface was studied through wetting theory. The contact
angle tests were performed to measure the surface energies
of bitumen and aggregate surfaces varying in both mineralogy
and roughness, based on which the interaction energies
between bitumen and aggregate in both air and water
environments were quantified, respectively. The negative
interfacial adhesive energy for the air/bitumen/aggregate
interface and interfacial debonding energy for the
water/bitumen/aggregate interface imply that both bitumen
wetting and water-induced bitumen dewetting on flat surface
are thermodynamically favorable. The Wenzel model was found
to describe the rough interface systems well. The
interfacial adhesive energy and interfacial debonding energy
are enhanced geometrically by the roughness factor r, which
indicates that the textured aggregate surface is in favor of
force-induced interfacial cracking resistance but leading to
an adverse effect on moisture damage resistance. The
interfacial cracking behavior of asphalt mixture was
exploited at the mesoscale through micromechanics method. A
micromechanical damage model was established by
incorporating the bilinear Cohesive Zone Model (CZM) into
the Mori-Tanaka model. It is found that the interfacial
debonding between bitumen and asphalt mortar exhibits a
significant dependency on the aggregate size. A critical
aggregate size has been identified, above which the damage
behavior of asphalt mixtures changes from hardening to
softening. The critical aggregate size increases as the
mortar modulus increases but decreases with the increase of
the interfacial stiffness, Poisson’s ratio of mortar, and
aggregate volume fraction. The interface strength and
fracture energy also show significant influences on the
fracture behavior of asphalt mixtures. The strength of
asphalt mixtures increases as the interface strength
increases, but it is independent of the fracture energy.
Increased fracture energy can improve the fracture
resistance of the asphalt mixture, while increased interface
strength has the opposite effect.In general, this thesis has
exploited a mechanistic investigation on the interfacial
interaction between bitumen and aggregate. The fundamental
knowledge regarding the influence factors as well as the way
how they works were created at multiple length/time scales.
The findings from this thesis open up an avenue for
predicting the bitumen-aggregate interfacial behavior based
on the material genomes.},
cin = {313410},
ddc = {624},
cid = {$I:(DE-82)313410_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2021-09995},
url = {https://publications.rwth-aachen.de/record/834563},
}
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