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Title:Quantitative evaluation of low-temperature performance of sustainable asphalt mixtures and binders containing recycled asphalt shingles (RAS) and rejuvenators
Author(s):Arnold, Jacob
Advisor(s):Reis, Henrique M.
Department / Program:Industrial&Enterprise Sys Eng
Discipline:Industrial Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Asphalt Concrete
Asphalt Binder
Recycled Asphalt Shingles
Acoustic Emission
Embrittlement Temperature
Disk-shaped Compact Tension (DC(T)) Tests
Mixing Temperature
Mixing Technique
Disk-shaped Compact Tension (DC(T))
Abstract:The utilization of recycled asphalt shingles (RAS) in HMA pavement applications was investigated via Disk-shaped Compact Tension (DC(T)) mixture testing and an acoustic emission (AE) based technique for estimating the embrittlement temperature of RAS-modified mixtures and asphalt binders prepared in the laboratory. During AE testing, the AE activities of mixture or binder specimens were monitored during cooling from room temperature to -50°C to estimate the onset of thermal cracking (i.e., the embrittlement temperature). The purpose of this research was to determine the influence of RAS on the low-temperature performance, and to investigate the effectiveness of rejuvenators on restoring any loss in said performance. The study was subdivided into three parts. Part 1 of the study examined HMA mixtures that contained varying amounts of RAS (0.0%, 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% by weight of the total mixture) which were prepared at three different mixing temperatures (120°C, 155°C, and 200°C). It was observed that mixtures containing RAS had lower DC(T) fracture energies, higher DC(T) peak loads, and warmer embrittlement temperatures. The results also showed that higher mixing temperatures appear to lower the embrittlement temperatures for mixtures containing RAS. Part 2 of the study evaluated the effect of varying amounts of rejuvenator (0.0%, 2.5%, 5.0%, 7.5%, 10.0%, 12.5%, and 25.0% by weight of the RAS binder) on HMA mixtures containing 7.5% RAS by weight of the total mixture. It was found that while DC(T) results were rather insensitive to rejuvenator content, the embrittlement temperature decreased (i.e., improved) with increasing rejuvenator content up to a saturation point at around 10.0% rejuvenator. Part 3 of the study tested thin, circular-shaped binder specimens containing finely graded (passing through sieve No. 50) RAS material (10.0% by weight of the binder) and varying amounts of a rejuvenator (0.0%, 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% by weight of the RAS binder), which was added to the RAS either before or after sieving. Issues with debonding between the granite substrate and the RAS-modified asphalt binder made AE testing rather challenging. These issues called for modifying the beam-shaped geometry that was used for the AE testing of unmodified binders in previous studies. The results did not show much change in the embrittlement temperature with increasing rejuvenator content, and it was conjectured that the thin geometry of the AE specimens governed the onset of thermal cracking more than the additives modifying the binder. Further modification of the AE testing of RAS-modified binders is required.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Jacob William Arnold
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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