Investigation of the aging phenomenon in asphalt binders and asphalt mixtures: linear viscoelastic behavior and performance properties
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Data
2023-01-17Primeiro membro da banca
Pereira, Deividi da Silva
Segundo membro da banca
Bueno, Lucas Dotto
Terceiro membro da banca
Nascimento, Luis Alberto Herrmann do
Quarto membro da banca
Capitão, Silvino Dias
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The analysis of the behavior of asphalt mixtures is extremely important in the paving scenario, whose
final objective is the best performance combined with resource savings. Accurate characterization and
prediction of mix properties is becoming more important as more accurate methods of predicting
pavement performance are being implemented. However, predicting the performance of asphalt
materials is still a challenging task, since numerous factors that affect asphalt materials still require
further investigation, including the aging phenomenon. Aging is generally defined as the change in
rheological properties from the change in chemical composition, and impacts on the performance of
pavements. In order to investigate these phenomena in the field and in the laboratory, eight monitored
segments were established in this research and had their materials (binders, aggregates and mixtures)
collected during the execution of the coating layer. The impact from laboratory aging protocols of
asphalt binders was investigated and indices to track oxidation levels were observed. Most rheological
indices found in the literature, and experimental data at intermediate and high temperatures, proved to
be good indicators of the aging phenomenon, and strongly correlate with chemical changes and fatigue
performance. Sample extraction and binder recovery at different depths were performed over time in the
field. The aging profile of the binders was observed from changes in the properties of the linear
viscoelastic domain (LVE), and the impact that these changes caused on the susceptibility to the main
defects of asphalt pavements: cracking due to fatigue and rutting. In general, stiffness gain and loss of
viscous portion were observed in response to deformations. Increased resistance to permanent
deformation, and fatigue behavior linked to imposed strain levels were also observed. Polymer
degradation during in-plant production severely impacted the SBS-modified binders. Equivalence time
of the RTFOT protocol with the production in the plant was observed. Verifications regarding the use
of reduced samples (38 mm x 110 mm) were carried out, and proved that this geometry generates reliable
results of complex modulus and fatigue behavior in asphalt mixtures. This investigation allowed the
study of mixtures aged in the field as built, from the horizontal extraction of samples, and also indicated
that air voids (linked to field compaction) is an important factor in the performance of the pavement and
in the costs throughout its service life. A multiscale analysis (binder/mixture/field) was carried out in
relation to resistance to permanent deformation and demonstrated that the behavior of the binder is
inherited by the pavement. Modified binders led to better performance of mixtures in the laboratory and
in the field. Verifications of the LVE behavior of the mixtures over field and laboratory aging were
carried out, and demonstrated that the mixtures gain stiffness in domains of high temperatures, and lose
a viscous portion for domains of low and intermediate temperatures. Correlation between time in field
and oven aging protocol were obtained. At the end, the fatigue performance analysis was evaluated
during the aging of the mixtures in the laboratory. Gain or loss of performance was observed depending
on the level of aging and level of imposed deformations. A strong relationship was obtained between
the fatigue resistance of the binders and the fatigue resistance of the mixtures.
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