Open AccessJournal Article
Testing Protocols to Ensure Performance of High Asphalt Binder Replacement Mixes Using RAP and RAS
Imad L. Al-Qadi,Hasan Ozer,John Lambros,Ahmad El Khatib,Punit Singhvi,Tamim Khan,Jose Rivera-Perez,Berangere Doll +7 more
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TLDR
In this paper, the authors developed and evaluated protocols, procedures, and specifications for testing engineering properties and performance of AC mixtures with high amounts (up to 60%) of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt concrete mixtures.Abstract:
The use of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt concrete (AC) mixtures can reduce demand for virgin aggregates and asphalt binder, bringing environmental and economic benefits. However, replacing virgin asphalt binder in AC mixtures poses challenges in terms of mixture volumetrics and low-temperature cracking, fatigue cracking, and other deterioration related to cracking. To counter these effects, softer virgin asphalt binder grades or modifying agents are used to improve production consistency. The purpose of this study was to develop and evaluate protocols, procedures, and specifications for testing engineering properties and performance of AC mixtures with high amounts (up to 60%) of RAP and RAS. The criteria for selection of the test method were (1) statistically significant spread in test outcome, representing a mix’s cracking resistance; (2) applicability and seamless implementation; (3) correlation to other independent test methods and engineering intuition; and (4) correlation to field performance. A practical test method, the Illinois modified semi-circular bending test (IL-SCB) was developed that can be readily implemented to quantify AC mixture’s cracking potential. In addition, a flexibility index (FI) was introduced to determine cracking resistance in a consistent way. The IL-SCB showed consistent and repeatable trends for changes in AC mix design properties. The developed FI was shown to provide greater separation between AC mixes to capture some of the changes that could not be captured by fracture energy alone. This approach does not enforce any limits on any AC mixture design characteristics, such as RAP and RAS content, or other alternative materials or technologies. Instead, it categorizes AC mixes based on their performance index. Hence, this approach encourages innovation and sustainability at the same time.read more
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Development of the fracture-based flexibility index for asphalt concrete cracking potential using modified semi-circle bending test parameters
TL;DR: In this paper, a fracture energy and flexibility index (FI) was proposed to screen asphalt concrete mixtures' cracking resistance using the semi-circular bending test geometry, and the results indicated positive correlation between SCB test results and other independent fatigue tests.
Journal ArticleDOI
Development of an IDEAL Cracking Test for Asphalt Mix Design and QC/QA
TL;DR: The focus in recent years has been to make asphalt mixes more affordable, and this has led to the increased use of recycled materials and binder modifications as discussed by the authors. Consequently, one often-heard complai...
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Evaluation of fracture resistance of asphalt mixes involving steel slag and RAP: Susceptibility to aging level and freeze and thaw cycles
Mansour Fakhri,Amin Ahmadi +1 more
TL;DR: In this paper, the effects of concurrent recycling of fine reclaimed asphalt pavement (RAP) and coarse steel slag aggregate (SSA) on fracture resistance of asphalt mixes were investigated.
Journal ArticleDOI
Comprehensive evaluation of low-temperature fracture indices for asphalt mixtures
TL;DR: For performance-based specifications and design processes, a number of cracking-related index parameters have been proposed for asphalt mixtures in recent years as mentioned in this paper, and several of these parameters have b...
Journal ArticleDOI
Characterising the long-term rejuvenating effectiveness of recycling agents on asphalt blends and mixtures with high RAP and RAS contents
TL;DR: In this article, the long-term rejuvenating effectiveness of recycling agents on asphalt blends and mixtures with high reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) contents was investigated.
References
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TL;DR: In this article, it was shown that at the base of the crack in the direction of its prolongation, the principal stresses are equal, thus tending toward a two-dimensional (two-dimensional) hydrostatic tension.
Book
Fracture and Size Effect in Concrete and Other Quasibrittle Materials
Zdeněk P. Bažant,Jaime Planas +1 more
TL;DR: In this paper, the authors used the Weibull-type approach to measure the effect of size effect on structural strength of a crack and its size effect in terms of the number of cracks and the size of the cracks.
Journal ArticleDOI
Applications of digital-image-correlation techniques to experimental mechanics
Journal ArticleDOI
Digital image correlation using Newton-Raphson method of partial differential correction
TL;DR: In this paper, the authors developed and limited experimental verification of a method which can determine displacements and gradients using the Newton-Raphson method of partial corrections, which was shown to be accurate in determining displacement and certain gradients, while using significantly less CPU time than the current coarse-fine search method.
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