Micromechanical investigation of phase separation in bitumen by combining atomic force microscopy with differential scanning calorimetry results

Das, Prabir Kumar; Kringos, Nicole; Wallqvist, Viveca; Birgisson, Björn

doi:10.1080/14680629.2013.774744

Cited by 122 publications

(70 citation statements)

References 22 publications

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“…In addition, and Pauli et al (2011) both discussed that the formation of bee structures cannot be attributed to just one factor, but rather a combination of factors and quite possibly may be the result of incompatibility of different molecular species interacting with one another. Das et al (2013) referred to this process as phase separation and described that the mobility of the different phases found within the bitumen correlated well with the results from differential calorimetry. They concluded that the phase separation mostly occurred within the crystallisation temperature range for each bitumen sample tested.…”

Section: Introductionmentioning

confidence: 76%

“…Based on this assumption, Allen used fracture mechanics to describe crack growth resulting from high tensile strains induced in the material. Das et al (2013) examined damage evolution by applying thermal cycles to various bitumen samples with different chemical compositions. They proposed that an increase in wax content increased crack formation during thermal cycling of bitumen samples.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of asphalt binder microstructure due to tensile loading determined using AFM and image analysis techniques

Jahangir

Little

Bhasin

2014

International Journal of Pavement Engineering

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In this study atomic force microscopy (AFM) creep indentations were performed to extract viscoelastic properties of the different domains (defined as microrheology) observed in bitumen samples from two different sources. The microrheology and geometry obtained using the AFM were used to perform finite element (FE) simulations to study the effect of bitumen microstructure on internal stress distribution. FE analyses suggest that microstructures with varying mechanical properties cause localised stress amplification that can lead to cracking/phase separation. A custom-made loading frame in conjunction with an AFM was used to examine the effects of tensile strain on bitumen microstructure. FE simulation and experimental results show that applying strain resulted in damage/phase separation concentrated in the interstitial zone between neighbouring bee structures, defined as load-induced phase separation. This study suggests that evaluating the bitumen microstructure and microrheology is critical to understanding the mechanisms of damage evolution in bitumen and engineering binders with higher inherent durability.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Evolution of asphalt binder microstructure due to tensile loading determined using AFM and image analysis techniques

Jahangir

Little

Bhasin

2014

International Journal of Pavement Engineering

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“…In contrast, almost every combination (high and low percentages) of the nonsaturate fractions resulted in similar bee structuring. Therefore, wax-induced or saturate-induced structure formation is perhaps the best conclusion, even though Das et al [195] underlined that the percentage of bee phases does not exactly correlate to the wax content of asphalt; therefore, the possibility of a complex structuring involving other asphalt components remains open. We can thus conclude that a cautious approach is necessary to avoid bee stings so that the expression "wax-induced phase separation" remains the most recommended one when referring to such structures.…”

Section: Surface Morphology: Afm (The Bees) and Semmentioning

confidence: 94%

“…Therefore, they concluded that i) the interaction between crystallizing paraffin waxes and the remaining nonwax asphalt components is responsible for much of the micro-structuring, including the bumble bee structures; ii) the structuring occurs in the nonpolar oil fraction, which contains most of the waxtype materials; and iii) the surface structuring depends on the wax type, wax concentration, and crystallizing conditions, as well as on the asphalt source. As it was well summarized by Das et al [195], "even though different research groups concluded significantly different reasons for the structures to appear and disappear, the extensive AFM studies have proved that asphalt has the tendency to phase separate under certain kinetic conditions and is highly dependent on the temperature history." This is why they coupled AFM and DSC studies and observed a direct correlation between the change of microstructures and the DSC results: the bees always appear during wax crystallization and disappear as the wax melt.…”

Section: Surface Morphology: Afm (The Bees) and Semmentioning

confidence: 95%

A review of the fundamentals of polymer-modified asphalts: Asphalt/polymer interactions and principles of compatibility

Polacco

Filippi

Merusi

et al. 2015

Advances in Colloid and Interface Science

526

184

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During the last decades, the number of vehicles per citizen as well as the traffic speed and load has dramatically increased. This sudden and somehow unplanned overloading has strongly shortened the life of pavements and increased its cost of maintenance and risks to users. In order to limit the deterioration of road networks, it is necessary to improve the quality and performance of pavements, which was achieved through the addition of a polymer to the bituminous binder. Since their introduction, polymer-modified asphalts have gained in importance during the second half of the twentieth century, and they now play a fundamental role in the field of road paving. With high-temperature and high-shear mixing with asphalt, the polymer incorporates asphalt molecules, thereby forming a swallowed network that involves the entire binder and results in a significant improvement of the viscoelastic properties in comparison with those of the unmodified binder. Such a process encounters the well-known difficulties related to the poor solubility of polymers, which limits the number of macromolecules able to not only form such a structure but also maintain it during high-temperature storage in static conditions, which may be necessary before laying the binder. Therefore, polymer-modified asphalts have been the subject of numerous studies aimed to understand and optimize their structure and storage stability, which gradually attracted polymer scientists into this field that was initially explored by civil engineers. The analytical techniques of polymer science have been applied to polymer-modified asphalts, which resulted in a good understanding of their internal structure. Nevertheless, the complexity and variability of asphalt composition rendered it nearly impossible to generalize the results and univocally predict the properties of a given polymer/asphalt pair. The aim of this paper is to review these aspects of polymer-modified asphalts. Together with a brief description of the specification and techniques proposed to quantify the storage stability, state-of-the-art knowledge about the internal structure and morphology of polymer-modified asphalts is presented. Moreover, the chemical, physical, and processing solutions suggested in the scientific and patent literature to improve storage stability are extensively discussed, with particular attention to an emerging class of asphalt binders in which the technologies of polymer-modified asphalts and polymer nanocomposites are combined. These polymer-modified asphalt nanocomposites have been introduced less than ten years ago and still do not meet the requirements of industrial practice, but they may constitute a solution for both the performance and storage requirements.

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“…Das, Kringos, Wallqvist, and Birgisson (2013) studied the influence of temperature on microstructures in bitumen by combining differential scanning calorimetry and AFM. It was found that the appearance of "bees" is always in the crystallisation temperature range of the same bitumen, while the dissolution of these microstructures could be related with the melting temperature range.…”

Section: Using Afm To Characterise Binder Homogenisationmentioning

confidence: 99%

Investigation on the microstructure of recycled asphalt shingle binder and its blending with virgin bitumen

Zhao

Nahar

Schmets

et al. 2015

Road Materials and Pavement Design

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Recycling waste roofing shingles into pavement construction has attracted more attention due to their high content of usable bitumen. Waste roofing shingles have gone through an airblowing process during production and are exposed to severe weather for many years during service life, which yields extremely aged asphalt binder. The difference in nature between virgin binder and binder from recycled asphalt shingle (RAS) has led to concerns over binder blending and compatibility of asphalt paving mixtures containing RAS. Therefore, usage of RAS has been commonly limited to a maximum of 3-5% incorporation. Currently, there is very little information in the literature that has addressed the RAS-virgin binder blending issues. This paper used atomic force microscopy (AFM) to characterise microstructural properties of the selected virgin, post-manufactured RAS and post-consumer RAS (tear-off) binders, as well as the temperature dependence of microstructure in one type of tear-off RAS binder. Meanwhile, the mode of interaction while bringing together virgin and RAS binders, that is, the extent of mixing or blending, was first observed in this study. According to the observations, AFM proved to be capable of differentiating virgin binder from RAS binder in terms of microstructure. The microstructure of tear-off RAS binder was found to be temperature dependent at moderate temperatures, but changed very little between 60°C and 180°C. Virgin binders selected in this study could not blend through an RAS-binder layer of 300 μm within 30 min at 180°C. Based on the observations, RAS binder was found to interact with virgin binder through "mixing" rather than "blending", in a mixing zone of 25-30 μm.

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Micromechanical investigation of phase separation in bitumen by combining atomic force microscopy with differential scanning calorimetry results

Cited by 122 publications

References 22 publications

Evolution of asphalt binder microstructure due to tensile loading determined using AFM and image analysis techniques

Evolution of asphalt binder microstructure due to tensile loading determined using AFM and image analysis techniques

A review of the fundamentals of polymer-modified asphalts: Asphalt/polymer interactions and principles of compatibility

Investigation on the microstructure of recycled asphalt shingle binder and its blending with virgin bitumen

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