Thermally Activated Healing of Fatigue Damage in Asphalt Binders
Thermally Activated Healing of Fatigue Damage in Asphalt Binders

Author: Quantao Liu

Publisher:

Published: 2016

Total Pages: 8

ISBN-13:

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Asphalt binder is a self-healing material and it has a potential to heal faster with increased temperatures. This paper investigates the thermally activated healing of fatigue damage in three asphalt binders, trying to answer the question: At what temperatures do asphalt binders heal? After fatiguing the sample, a heating treatment was applied and the sample was fatigued for the second time. The recovered fatigue life and the recovered accumulated dissipated energy are used to quantify the thermally activated healing rates of asphalt binders. It is found that these two healing indexes coincide well with each other in different healing conditions. Base asphalt binders can heal the fatigue damage completely after heating for 20 min at the softening-point temperatures. Styrene-butadiene-styrene (SBS)-modified asphalt binder can achieve full healing at a temperature 20°C below its softening point, where the elastic recovery of the SBS chain segment may play an important role in healing. It is also found that healing of fatigue damage in asphalt binder is highly strain dependent: the healing ratio is higher at high strain amplitude. It proved that thermally activated healing can be repeated when damage returns in asphalt binder. It is concluded that thermally activated healing of fatigue damage is definitely useful to increase the fatigue life of asphalt binders and different asphalt binders should be heated to certain temperatures related to their specific softening points.

Evaluation of Asphalt Binder and Asphalt Mixture Healing Based on Visco-Elastic Continuum Damage Theory
Evaluation of Asphalt Binder and Asphalt Mixture Healing Based on Visco-Elastic Continuum Damage Theory

Author: Amirmohammad Bahadori

Publisher:

Published: 2020

Total Pages: 137

ISBN-13:

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Fatigue cracking of asphalt pavements is one of the main distresses that reduces the serviceability of roads. The prediction of fatigue cracking in pavements is carried out using laboratory tests and mechanistic models. However, such predictions usually underestimate observed field performance. Their inability to suitably account for the self-healing capability of asphalt pavements is one of the key sources of the variation. This study presents a novel test method and a healing index based on Visco-Elastic Continuum Damage (VECD) theory to quantify the self-healing capacity of asphalt binders and mixes. The proposed asphalt binder healing test is a modification of the conventional Linear Amplitude Sweep (LAS) test, which not only considers the effect of rest periods but also minimizes the number of specimens required for the comprehensive analysis.A healing index based on released pseudo strain energy was developed to quantify the healing of asphalt binder and mixes. The analyses of healing indices for asphalt binders show that softer binders have better healing capacity at low damage levels. On the other hand, binders with higher performance grade have better healing capacity at higher damage levels. An increase in rest period duration was found to increase the healing index of asphalt binder. But the sensitivity of the healing index to the duration of rest periods decreased with damage accumulation. Studies conducted on the surface energy and intrinsic healing parameters of asphalt binder showed that the non-polar Lifshitz0́3van der Waals component of the surface energy correlated well with the healing of asphalt binder.In addition, stress-controlled fatigue tests with rest periods were used to study the healing of asphalt mixtures. The results showed that an increase in temperature and rest period duration enhanced the healing of asphalt mixes. Finally, the rest period, temperature, material integrity level, and surface energy of the asphalt binder were used to develop a phenomenological-based healing prediction model. It was verified on the healing results of a sample mix. The results of the statistical analysis of the variables demonstrated that the temperature had the highest effect on the healing of asphalt mixes.

Laboratory Investigation of a Novel Method to Accelerate Healing in Asphalt Mixtures Using Thermal Treatment
Laboratory Investigation of a Novel Method to Accelerate Healing in Asphalt Mixtures Using Thermal Treatment

Author: Amit Bhasin

Publisher:

Published: 2009

Total Pages: 22

ISBN-13:

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Asphalt binders have an inherent ability to reverse damage in the form of micro-cracks that is caused due to the repeated action of external loads. This reversal occurs during rest periods between load cycles. The phenomenon of crack reversal is referred to as autogenous or self-healing. The main objective of this project was to apply established principles of healing to investigate a novel technique to accelerate reversal of accumulated micro-crack in asphalt mixtures. This technique was developed and evaluated using a laboratory scale set up. Laboratory tests were used to evaluate the impact of thermal treatment on the fatigue cracking life of asphalt mixtures. Results from this study indicate that for two out of the three different types of asphalt mixtures, intermittent application of the thermal treatment resulted in approximately 50% increase in the fatigue cracking life of the mixture.

Understanding Mechanisms Leading to Asphalt Binder Fatigue
Understanding Mechanisms Leading to Asphalt Binder Fatigue

Author:

Publisher:

Published: 2012

Total Pages: 0

ISBN-13:

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Fatigue cracking is one of the primary modes of failure in asphalt pavements. Cracking typically occurs within the asphalt binder phase of asphalt mixtures. Thus, asphalt binder fatigue resistance is critical in determining overall pavement fatigue performance. One procedure commonly used to characterize asphalt binder fatigue resistance is the time sweep test, which consists of repeated torsional loading of a cylindrical specimen in the Dynamic Shear Rheometer (DSR). Generally, apparent changes in material properties with respect to number of cycles of loading are used to define fatigue failure of the asphalt binder. Results of this test have been shown to correlate well with asphalt mixture fatigue performance. However, the mechanisms responsible for changes in material properties during fatigue testing in the DSR were previously not well understood. Results in this study demonstrate that fracture can account for changes in loading resistance of asphalt binders during time sweep testing. Under cyclic torsional loading of cylindrical specimens, macro fracture is shown to manifest in the form of edge fracture. Edge fracture is a circumferential crack starting at the periphery of a cylindrical sample that propagates inward as loading is applied, reducing the effective sample size. Digital visualization of the fractured specimens allowed for determination of the fractured and intact sample area. Predictions of fracture propagation based on measurements of loading resistance and fracture mechanics concepts agreed favorably with actual measurements based on visualization. Furthermore, the fracture morphology and progression of crack growth of asphalt binders matched those observed for other materials under similar loading conditions. Based on these results, fatigue damage characterization of asphalt binders can be improved by incorporating fracture mechanics into an analysis framework for DSR fatigue test results. An analysis framework based on fracture principles is presented. The proposed model allows predicting fatigue life at any loading amplitude using the results of a single fatigue test. Additionally, it is demonstrated that time-temperature superposition is applicable to fatigue crack propagation of asphalt binders, allowing for efficient prediction of fatigue performance at multiple temperatures. The model is validated using a comparison between asphalt mixture and binder fatigue test results.

Fracture and Viscoelastic Properties of Asphalt Binders During Fatigue and Rest Periods
Fracture and Viscoelastic Properties of Asphalt Binders During Fatigue and Rest Periods

Author: Shihui Shen

Publisher:

Published: 2014

Total Pages: 10

ISBN-13:

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Viscoelastic asphalt binder plays an important role in bonding individual aggregate particles and contributes to the durability and stability of asphalt pavement. When asphalt binder is subjected to cyclic loading, deformation and fracture may develop simultaneously within it, leading to the deterioration of material properties and eventually fatigue failure. Research has found that some degree of recovery may develop if rest periods are applied after fatigue deterioration. However, it is not clear whether such recovery is caused by fracture healing, viscoelastic recovery, or both. This paper presents an analysis to differentiate the contributions of fracture healing and viscoelastic recovery to the asphalt binder during rest periods. It also evaluates the damage caused by deformation and fracture during a fatigue process. It is found that viscoelastic recovery plays an important role in the instant increase in the dynamic shear modulus at the beginning of the rest period. The effect of fracture healing on dynamic shear modulus recovery is more dominant in the long term. A healing index is developed based only on the fracture healing of asphalt binder, excluding the effect of viscoelastic recovery. It can be used to evaluate the true healing properties of different asphalt binders.

Fracture Properties and Fatigue Cracking Resistance of Asphalt Binders
Fracture Properties and Fatigue Cracking Resistance of Asphalt Binders

Author: Arash Motamed

Publisher:

Published: 2012

Total Pages: 72

ISBN-13:

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Several different types of modifiers are increasingly being used to improve the performance of asphalt binders or to achieve desired mixture production characteristics (e.g., Warm Mix Asphalt). However, current Superpave performance specifications do not accurately reflect the performance characteristics of these modified binders. The main objective of this study was to evaluate the inherent fatigue cracking resistance of asphalt binders in the form of a matrix with rigid particle inclusions. The underlying rationale for this approach was to subject the binders to a state of stress that is similar to the one in a full asphalt mixture. This was achieved by fabricating and testing composite specimens of the asphalt binders and glass beads with a specified gradation. Four asphalt binders with similar true temperature grades but different modifiers were used in this study. The viscoelastic and fatigue cracking characteristics of the binders were measured using the glass bead-binder composite specimens in a dynamic shear rheometer at an intermediate temperature. The results demonstrate that the four asphalt binders modified using different methods had different damage characteristics despite the fact that these four binders were rated to have a similar performance grade based on the Superpave specifications. Fatigue cracking characteristics of the glass bead-binder test specimens used in this study were qualitatively very similar to the fatigue cracking characteristics of full asphalt mixtures using the same binders. The rank order of fatigue cracking resistance for the four glass bead-binder mixtures compared reasonably well to the rank order of fatigue cracking resistance for the full asphalt mixtures that incorporated these asphalt binders.

Self-Healing Construction Materials
Self-Healing Construction Materials

Author: Antonios Kanellopoulos

Publisher: Springer Nature

Published: 2021-12-08

Total Pages: 228

ISBN-13: 303086880X

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This book provides a thorough overview of all techniques for producing self-healing construction materials. Construction materials (cement-based, bituminous, metals, and alloys) are prone to cracking, which with the progress of time can lead to compromising of the structural integrity of critical infrastructure. Self-healing materials form a new class of materials that have inbuilt engineered properties to counteract damage and repair it before it becomes critical. The methods for monitoring, modeling, and assessing self-healing are also reviewed. The final section of the book discusses the future outlook and potential extension of self-healing concepts to other materials (e.g., heritage structures and soils).

Self-Healing Polymers
Self-Healing Polymers

Author: Wolfgang H. Binder

Publisher: John Wiley & Sons

Published: 2013-03-29

Total Pages: 638

ISBN-13: 3527670203

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Self-healing is a well-known phenomenon in nature: a broken bone merges after some time and if skin is damaged, the wound will stop bleeding and heals again. This concept can be mimicked in order to create polymeric materials with the ability to regenerate after they have suffered degradation or wear. Already realized applications are used in aerospace engineering, and current research in this fascinating field shows how different self-healing mechanisms proven successful by nature can be adapted to produce even more versatile materials. The book combines the knowledge of an international panel of experts in the field and provides the reader with chemical and physical concepts for self-healing polymers, including aspects of biomimetic processes of healing in nature. It shows how to design self-healing polymers and explains the dynamics in these systems. Different self-healing concepts such as encapsulated systems and supramolecular systems are detailed. Chapters on analysis and friction detection in self-healing polymers and on applications round off the book.