Impact of laboratory simulated aging on asphalt concrete flexibility

Zhu, Zehui

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https://hdl.handle.net/2142/102939 Copy

Description

Title

Impact of laboratory simulated aging on asphalt concrete flexibility

Author(s)

Zhu, Zehui

Issue Date

2018-12-05

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

• Al-Qadi, Imad L.
• Ozer, Hasan

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Asphalt concrete
• Flexibility index
• Long-term aging
• Aging rate
• Mixture design

Abstract

The aging of asphalt materials is considered an important factor contributing to the deterioration of asphalt concrete (AC) pavements. Asphalt binder aging is a combination of various complex mechanisms that affect its rheological properties causing AC to become stiffer and more brittle. As a result of aging, the resistance of AC pavements to various forms of cracking including fatigue, thermal, and/or block is reduced. Hence, AC aging presents challenges for preserving an adequate level of pavement serviceability. Therefore, it is critical to understand the effect of aging on AC pavement cracking development and identify the effect of AC mix design parameters on the aging rate. A wide range of AC mixes were investigated in this study using the Illinois Flexibility Index Test (I-FIT) after the specimens were subjected to various lab-simulated long-term aging conditions. The flexibility index (FI), an outcome of the I-FIT and a measure of the AC flexibility. decreases consistently after long-term aging. This effect is primarily due to changes in the post-peak slope, an indication of crack propagation speed. The impact of aging on various AC mixtures varies and results in different FI deductions because of the mix type and aging condition. Simple and multiple linear regression were used to analyze the impact of mix design parameters on AC aging rate. The effect of voids in mineral aggregate (VMA), low-temperature performance-grade (PG), asphalt binder replacement (ABR), AC mix type, water absorption of the aggregate blend, and effective asphalt binder content was found to be significant. Several aging levels were examined using a conventional oven and utilizing both compacted and loose AC mixes. The various aging levels were compared to the standard five-day aging at 85oC (5D/85C). The study found that aging compacted I-FIT specimens at 3D/95C is practical and is equivalent to that at 5D/85. Additionally, because the parameters impacting aging at 1D/95C and 3D/95C are the same and have the same trend, 1D/95C may be used as an initial indicator for long-term aging.

Graduation Semester

2018-12

Type of Resource

text

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http://hdl.handle.net/2142/102939

Copyright and License Information

Copyright 2018 Zehui Zhu

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