Multi-scale studies of aging, rejuvenation, and extrinsic self-healing in bituminous materials

Lu, Yujia

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https://hdl.handle.net/2142/124690 Copy

Description

Title

Multi-scale studies of aging, rejuvenation, and extrinsic self-healing in bituminous materials

Author(s)

Lu, Yujia

Issue Date

2024-04-23

Director of Research (if dissertation) or Advisor (if thesis)

Hajj, Ramez

Doctoral Committee Chair(s)

Hajj, Ramez

Committee Member(s)

• Al-Qadi, Imad
• Tutumluer, Erol
• Garg, Nishant
• Wang, Hao

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Asphalt materials
• flexible pavements
• multi-scale studies
• aging
• rejuvenation
• self-healing
• pavement damage
• recycled materials

Abstract

Oxidative aging is a crucial factor that influences the performance of asphalt mixes in flexible pavements. The aged asphalt mix is more susceptible to fatigue and thermal cracking, the most critical distress at intermediate and low temperatures, respectively. An emerging technology to mitigate the cracking of asphalt pavements is the use of self-healing capsules embedded in asphalt mixtures. However, the development of self-healing capsules is at the early technology stage in which it must be well-defined at the lab scale. There is a need to design self-healing capsules with the understanding of the aging and rejuvenation mechanisms from chemical, mechanical, and morphological structural changes within asphalt. To understand extended asphalt aging, asphalt binders were characterized at multiple aging levels and length scales. The time-sensitive asphalt binder microstructures were found and correlated across scales with a recently validated asphalt binder cracking test, the poker chip test. The correlation coefficient between ductility and micro-morphological features was 0.98, which indicated that the beam damage phenomenon of the surface morphology using a Scanning Electron Microscope directly related to nonlinear cracking in a realistic stress state. These methods related directly to polymer degradation at extended aging levels, which could not be represented by linear or nonlinear rheology. Based on the high quantities of dosing combination for obtaining the trend of dosing rejuvenators, this dissertation proposed a dosage determination approach considering multiple criteria in both cracking and rutting potential, including true low PG, ∆Tc, ductility, and strength. Because the dominant effect of virgin asphalt binder with less than 30% ABR in asphalt blends was realized in this dissertation, the optimal dosage efficiency was also suggested to consider the response on long-term aging effect of rejuvenated asphalt. For optimizing the encapsulated rejuvenators for pavement self-healing, this research evaluated a range of design factors-healing agent type, concentration, capsule shell thickness, and capsule percentages. Applicable scenarios for using each capsule were proposed and expanded from the fine aggregate matrix (FAM) scale to the asphalt concrete (AC) scale. Even though addition of Sodium alginate and Calcium chloride increased the strength of capsules, up to 5% of sodium alginate and 4% Calcium chloride could make a difference in healing different damage levels. Oil to water ratios higher than 0.5 were helpful for high damage areas while more than 2% of capsule content in asphalt mixes could increase integrated healing efficiency by increasing capsule distribution. This work showed the value of applying different capsules for distinct stress states in combination with each other. Finally, this work verified benefits of capsules by comparing their use to solely rejuvenating at the asphalt concrete level. 16% rejuvenator by weight of binder did not increase healing, but damaged the mix as a result of low stiffness. However, capsules could take advantage of high amounts of rejuvenators, up to 16%, and gradually release healing agents with loading. In this dissertation, asphalt material characterization tools were explored and provided micro morphology damage indicators, chemical analysis, and cracking tolerance analysis methods based on the understanding of extended aging. This dissertation also revealed that both optimum dosages and fundamental mechanisms of rejuvenation were affected by rejuvenator type, base binder selection, recycled material content, and the aging level of the binder. The prospect of extrinsic self-healing asphalt was advanced greatly in this dissertation. Although rutting potential existed in the mixtures with high oil contents or bio-oil rejuvenator, the appropriate capsule design and application of various types of capsules in asphalt pavement can result in self-healing within asphalt pavements at various damage degrees and locations. The derived healing index based on viscoelastic continuum damage (VECD) facilitated the selection of capsule designs. Results were also consistent across micro-scale spectroscopy experiments and the mixture-level testing. This research therefore established a framework for engineering a combination of capsules for use at pavement scale based on an understanding of chemical interactions, mechanical properties, and multi-scale experimental verification. It is possible in the future to utilize the proposed dosing protocol to optimize rejuvenator use for efficiently solving aging problems. Moreover, the multiscale study framework could assist researchers and practitioners to develop the self-healing capsules that meet their own requirements. This framework will, in the long term, result in increased use of recycled materials, longer lasting pavements, and mitigation of oxidative aging.

Graduation Semester

2024-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2024 Yujia Lu

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