Differential Scanning Calorimetry Study of Asphalt Crystallinity

Daly, William H.; Qiu, Zhaoyao

doi:10.3141/1535-08

Cited by 10 publications

(10 citation statements)

References 7 publications

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“…The dissolution of the crystalline fraction formed upon rapid cooling causes an endotherm on the reversing curve of the unannealed (0 h) bitumen (Figure a). The large width and smooth profile shape of the endotherm prove that, upon crystallization of the wax molecules, mixed structures differing in size and perfection were formed. , However, the endothermic profile is simpler than one that might be expected from the compound complexity of bitumens . The metastability of the formed structures is confirmed by an almost fully reversible dissolution (any endothermic signal is absent on the nonreversing curve of the unannealed (0 h) sample in Figure b), because the forming crystals are so small and defective that they have time to dissolve and recrystallize during the temperature modulation cycle. ,, As the annealing time increases, the endothermic background on the reversing curves decreases, almost disappearing on the 16-h curve.…”

Section: Resultsmentioning

confidence: 90%

“…The distinct crystal populations in bitumen suggest distinct patterns of the DSC curves which depend on their chemical structure, and their interaction with the amorphous phase and with each other. , The CF of bitumen is represented by the waxes which a polydisperse mixture of polymethylene chain compounds (alkanes) divided into macro- and microcrystalline waxes. − Unlike macrocrystalline waxes, which consist primarily of n -alkanes, microcrystalline waxes are dominated by iso- and cycloalkanes. Differences between the bitumen waxes are also reflected in their thermal analyses. ,, In general, waxes with a predominance of n -alkanes melt and crystallize within a narrower and higher temperature range.…”

Section: Resultsmentioning

confidence: 99%

“…Due to this, the wax crystals would be small and well-dispersed in the oil medium of bitumen . The wax crystals in bitumen result from the cocrystallization of the wax methylene chains . Although the wax of bitumen contains numerous components, the primary crystallizing component is the higher molecular weight n -alkanes ,, because they need no deep supercooling .…”

Section: Resultsmentioning

confidence: 99%

“…The further formation of wax crystals occurs in order of descending molecular weight. Since aliphatic hydrocarbons are able to fit into a similar crystal lattice, the same process could occur in the wax of bitumen . With a faster growth rate, the shorter chains are trapped by the fast crystallization of the longer chains, which results in a solid solution formation. , The presence of another hydrocarbon facilitates the formation of the solid solution. , Thus, fast cooling in the bitumen results in the metastable dispersion of small, imperfect wax crystals suspended in the liquid oil phase. , …”

Section: Resultsmentioning

confidence: 99%

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Interpretation of Double-Peak Endotherm on DSC Heating Curves of Bitumen

et al. 2020

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Since the late 1960s, differential scanning calorimetry (DSC) has been used to characterize petroleum bitumen, in particular, for the determination of the crystallized fraction (CF) content. This procedure is based on the construction of a baseline after identifying the CF dissolution endotherm on the heating curve. However, many bitumens commonly exhibit double-peak endotherms during a DSC heating scan. In this case, the task of constructing the corresponding baseline does not have a unique solution because the interpretation of the heat flow profile is ambiguous. Several interpretations have been proposed earlier to explain the origins of the double-peak endotherm. However, the double-peak endotherm is currently still not fully understood, and a comprehensive consensus has not been achieved. If the determination of the baseline location is incorrect, the CF content can be over- or underestimated by 20–30%. In the current work, double-peak endotherm behavior was investigated by temperature modulation DSC. All of the earlier explanations were critically considered. The origin of the double-peak endotherm was discussed in detail, and a probable descriptive model for the formation of the double-peak endotherm was suggested. The endotherm pattern is assumed to be governed by three overlapping thermal events: a broad endothermic background and a twin “recrystallization exotherm–dissolution endotherm” pair. The onset of the recrystallization exotherm and the intensity of both events depend on the annealing temperature and time. The study promotes a better understanding of the relationship between the thermal effects on the DSC curves and the structural changes of bitumen. A correct interpretation of the double-peak endotherm can provide a more exact determination of the CF content in bitumen.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Interpretation of Double-Peak Endotherm on DSC Heating Curves of Bitumen

et al. 2020

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“…The glass transition of bitumen region is very wide, covering a range broader than 50°C due to the occurrence of several transitions that can partially overlap taking place at different temperatures in the different bitumen fractions (Daly et al 1996). A glass transition temperature (Tg) can thus be defined, located within the overall transition range.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Combined Effects of Physical Hardening and Chemical Ageing on Low Temperature Properties of Bituminous Binders

et al. 2015

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Physical hardening is a phenomenon that takes place at low temperatures, producing time-dependent isothermal changes in the rheological properties of bituminous binders. Stiffening effects caused by physical hardening combine with those consequent to chemical ageing, thus promoting the build-up of thermally-induced stresses which may lead to premature pavement failure. The main goal of this paper was to investigate the influence of physical hardening on low temperature properties of bituminous binders tested in different ageing conditions. Moreover, reversibility of hardening phenomena was directly assessed by means of a dedicated testing protocol. The study, carried out by making use of the Bending Beam Rheometer (BBR), considered four binders of different type and origin (two neat bitumens and two commercial SBS polymer-modified binders) and three ageing conditions (original, short-term ageing and long-term ageing). Obtained results, expressed in terms of a Physical Hardening Rate (PHR), showed a significant effect of chemical ageing on low temperature hardening of binders. In particular, rate of hardening was found to vary with temperature and to decrease with degree of ageing. Reversibility of the hardening process was also verified.

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Investigation of flow properties of asphalt binders containing polymer modifiers

et al. 2008

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Modified asphalts using polymeric additives, including isotactic polypropylene (iPP) and different degrees of chlorinated polypropylene (CPP), have been prepared and examined using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), rotational viscometer, and dynamic shear rheometer (DSR) in this study. The results of DSC studies show that different levels of the crystallization occur in asphalt/iPP blends because most of the crystallinity of iPP remain intact in the blend, while those asphalt samples having CPP tend to affect the thermal behavior in the DSC thermograms because of increasing the amorphous region of CPP. From the images of SEM, the distinctions of the phase distributions between the asphalt/iPP and asphalt/CPP blends illustrate that the chlorine content in CPP is a significant factor in controlling its compatibility with asphalt. The rheological studies show that the asphalt blends containing CPP (26 wt% of Cl) exhibit higher viscosity in terms of higher temperature to get Newtonian behavior and display superior rutting resistance to avoid permanent deformation at high temperature. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

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Differential Scanning Calorimetry Study of Asphalt Crystallinity

Cited by 10 publications

References 7 publications

Interpretation of Double-Peak Endotherm on DSC Heating Curves of Bitumen

Interpretation of Double-Peak Endotherm on DSC Heating Curves of Bitumen

Experimental Investigation on the Combined Effects of Physical Hardening and Chemical Ageing on Low Temperature Properties of Bituminous Binders

Investigation of flow properties of asphalt binders containing polymer modifiers

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