Embed Size (px)
Citation preview
This article was downloaded by: [McGill University Library]On: 12 March 2013, At: 22:01Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Road Materials and Pavement DesignPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/trmp20
Physicochemical properties ofbitumens modified with biofluxMarkus Simonen a , Timo Blomberg b , Terhi Pellinen c & JarkkoValtonen ca A-Insinöörit Suunnittelu Oy, Espoo, Finlandb Nynas Oy, Vantaa, Finlandc Department of Civil and Environmental Engineering, AaltoUniversity, Aalto, FinlandVersion of record first published: 05 Nov 2012.
To cite this article: Markus Simonen , Timo Blomberg , Terhi Pellinen & Jarkko Valtonen (2013):Physicochemical properties of bitumens modified with bioflux, Road Materials and PavementDesign, 14:1, 36-48
To link to this article: http://dx.doi.org/10.1080/14680629.2012.735798
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representationthat the contents will be complete or accurate or up to date. The accuracy of anyinstructions, formulae, and drug doses should be independently verified with primarysources. The publisher shall not be liable for any loss, actions, claims, proceedings,demand, or costs or damages whatsoever or howsoever caused arising directly orindirectly in connection with or arising out of the use of this material.
Road Materials and Pavement Design, 2013Vol. 14, No. 1, 36–48, http://dx.doi.org/10.1080/14680629.2012.735798
Physicochemical properties of bitumens modified with bioflux
Markus Simonena, Timo Blombergb, Terhi Pellinenc* and Jarkko Valtonenc
aA-Insinöörit Suunnittelu Oy, Espoo, Finland; bNynas Oy, Vantaa, Finland; cDepartment of Civil andEnvironmental Engineering, Aalto University, Aalto, Finland
Five laboratory-produced cut-back bitumens with same target viscosity of 600 mm2/s at 60◦Cwere investigated to determine the effect of chemical composition on the rheological proper-ties. Studied cut-back bitumens comprised four bioflux-modified bitumens and one traditionalslow-curing cut-back bitumen as a reference. The generic fractions (saturates, aromatics, resinsand asphaltenes) of base bitumens (viscosities of about 1500, 3000, 6000 and 37,000 mm2/sat 60◦C) were quantified by thin-layer chromatographic method with flame-ionisation detec-tion (IATROSCAN MK-6s) and the rheological properties of the base bitumens and cut-backbitumens were studied with a Physica 301 rheometer. The soft base bitumens (viscosity≤6000 mm2/s at 60◦C) and their biofluxed solutions proved to be rheologically complex,which was witnessed by wax crystallisation and melting phenomena observed at temperaturesbetween 10 and 30◦C. The harder base bitumens with higher asphaltene content did not exhibitnoticeable crystallisation. The low polarity and low molecular weight of the bioflux solventreduced the stiffnesses of cut-back bitumens remarkably under 30◦C. Thus, the compositionof cut-back bitumens had a significant effect on the rheology of blends, although the targetviscosities at 60◦C were the same.
Keywords: bioflux; fluxed bitumen; cut-back bitumen; crystallisation; saturates; aromatics;resins; asphaltenes; rheology
1. Introduction1.1. BackgroundBitumen is modified to fulfil the requirements in diverse applications ranging from road pavementsand roofing industry to various waterproofing materials. Bitumen modified with petroleum-basedvolatile solvents known as cut-back bitumen or with relatively non-volatile fluxing agent referredas fluxed bitumen are widely used in pavement industry for stockpiled cold patching mixtures.The purpose of bitumen modification is to lower their viscosity, and thus secure the workability ofthe mixture after manufacturing and storing. Mixture stability will be gained through evaporationof solvents at service. Volatile organic compounds are considered to be harmful for the environ-ment (IPCC, 2001); therefore bio-based fluxing agents and binders have recently been studied asreplacements for the traditional binders containing volatile solvents.
The composition and structure of bitumen is complex. Currently bitumen is characterised asdispersed polar fluid (Petersen et al., 1994; Redelius, 2004), though some researchers still supportthe colloidal model originally established by Nellensteyn in the 1920s (Lesueur, 2009). However,an agreement exists on characterising chemical and physical properties of bitumen includingchemical composition and rheological behaviour. The complexity is evident, when bituminousbinders with equal grading are studied extensively in a wide range of temperatures (Griffin,
*Corresponding author. Email: [email protected]
© 2013 Taylor & Francis
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 37
Simpson, & Miles, 1959; Loeber, Muller, Morel, & Sutton, 1998; Lu & Isacsson, 2002). Equallygraded bitumens may vary in temperature susceptibility, elasticity, viscosity, age-hardening, andhealing. In the early 90s, the first Strategic Highway Research Program (SHRP) introduced theSuperpave performance grading that better covers bitumen properties in the whole temperaturerange.
Rheological measuring systems widely utilised in polymer science have increasingly attractedresearchers of bituminous binders over the last two decades. Initially, small-strain dynamic studiesof polymers and polymer solutions were first published as early as 1930s according to Doraiswamy(2002). Complex shear moduli and phase angles of bituminous binders are typically measured inlinear viscoelastic (LVE) region in order to keep the analysis simple and straightforward (Andersonet al., 1994). The limits for linear viscoelasticity are determined by strain sweep at differenttemperatures and frequencies (Airey & Rahimzadeh, 2004; Anderson et al., 1994). The strainrange for LVE region suggested in EN-standard 14770 (Suomen Standardisoimisliitto, 2005) forunmodified bitumens is 0.005–0.100.
Viscoelastic properties of polymers (e.g. storage modulus, loss modulus, phase angle) mea-sured at various temperatures can be shifted to form a unified master curve as a function ofa reduced variable (loading frequency or time) at a reference temperature (Ferry, 1970). Theabove-mentioned shifting procedure is based on time–temperature superposition (TTSP) and thematerials which it can be applied to are referred as rheologically simple. Ferry (1970) lists threecriteria for the applicability of TTSP: (I) exact matching of shapes of adjacent curves, (II) shiftfactor (at) for all viscoelastic functions are the same and (III) the temperature dependence of atmust have a reasonable form. Anderson et al. (1994) concluded on the basis of dynamic shearrheometer measurements that TTSP is valid for asphalt cements. However, failures in TTSP havebeen observed within waxy bitumens (Lesueur et al., 1996; Soenen, De Visscher, Vanelstraete,& Redelius, 2006), bitumen with high asphaltene content (Lesueur et al., 1996; da Silva, deCamargo Forte, de Alencastro Vignol, & Cardozo, 2004) and bitumens modified with polymers(Airey, 2002).
Reasons for differences among bitumens being the same grade have been explained by thevarying composition. The composition of bitumen is usually presented with four generic frac-tions: saturates, aromatics, resins and asphaltenes (SARA fractions) (Jewell, Albaugh, Davis, &Ruberto, 1974). Although SARA analysis discriminates only with respect to polarity and solu-bility, each fraction shares quite similar molecular size, constitution and polarity; saturates arethe least complex and least polar molecules, whereas asphaltenes are the most complex and mostpolar ones (Lesueur, 2009). Changes in the bitumen structure and its fractions as function oftemperature are traced with differential scanning calorimetry (DSC) or modulated DSC (MDSC)technique. Claudy, Letoffe, King, Planche, and Brule (1991) were among the first ones to studyglass-transition temperature of the hydrocarbon matrix and the crystallised fractions of pavingasphalts. They concluded that class transition is attributed partly to the aromatic fraction andpartly to the saturated fraction. They also observed on warming an endothermal effect corre-sponding to the dissolution of crystallised molecules present in the saturate fraction. Masson andPolomark (2001) stated that each SARA fraction has at least two glass-transition temperaturesand bitumen four according to their MDSC studies. Glass-transition temperatures are related tomobility of molecules and therefore changes in physical structure of bitumen as temperaturevaries.
Because physical properties, such as viscosity and modulus, are dependent on chemical andphysical structure of bitumen, the SARA fractions and their properties are used in interpreting thedifferences between bitumens. On the basis of the study by Domke, Davison, and Glover (1999)and Michalica, Kazatchkov, Stastna, and Zanzotto (2008) it can be concluded that the contentand chemical characteristics of low-polar fractions (saturates, aromatics and waxes) dominate
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
38 M. Simonen et al.
the low-temperature properties whereas high-polar fraction (asphaltenes) dominate the high-temperature properties. Michalica et al. compared two bitumens of different origin and foundthat low molecular weight and high heteroatom content of low-polar fractions (saturates and aro-matics) together with higher asphaltene content led to more desirable low-temperature (bettercracking resistance) as well as high-temperature behaviour (better rutting resistance). Althoughresearch on this subject has been intensive, an ultimate model for predicting the performanceof bitumens based on chemical compositions is still unpublished. However, as a part of SHRPreport A-367 (Petersen et al., 1994) chemical composition was statistically related to the bitumenperformance through several parameters employed in rheological models for bitumen.
Blending bitumen with low viscosity fluid (e.g. volatile solvent or fluxing agent) leads toa viscosity lower than that of the base bitumen. Numerous mixing rules for calculating blendviscosities have been suggested by several authors (Centeno, Sánchez-Reyna, Ancheyta, Muñoz,& Cardona, 2011). The viscosity of biofluxed bitumens has been found to obey approximatelyEquation (1) (Davison et al., 1994; Epps, Little, Holmgreen, & Terrel, 1980).
log10(log10(η12)) = x × log10(log10(η1)) + (1 − x) × log10(log10(η2)), (1)
where x is the content of component 1, η1 is the viscosity of the component 1, η2 is the viscosityof the component 2 and η12 is the viscosity of the blend.
1.2. Objective“Bioflux” (not registered trademark) is one of the recently introduced bio-based fluxing agents.It is a product of a chemical process called NExBTL, which is patented by Neste Oil. The feed ofNExBTL process consists of vegetable oils, animal fats and hydrogen. Bioflux, i.e. flux from bio-based raw materials, consists of 100% linear and branched C10–C20 alkanes and its distillationregion (boiling point) ranges from 180 to 320◦C. Density at 15◦C is 770–790 kg/m3 and viscosityat 60◦ is c. 2 mm2/s. In 2008, Valtonen, Pellinen, and Blomberg (2010) reported field study onbitumens modified with bioflux. Only one composition of biofluxed bitumen was included andthere were no extensive studies on binder properties. In general, there is only few or no publishedresearch on the rheology of soft and fluxed bitumens.
The main objective of this study was to evaluate and compare the rheological properties ofbiofluxed bitumens having approximately the same viscosity at 60◦C temperature. The propertiesof common soft bitumens, used as base bitumens for biofluxed products, were also studied because,on the basis of literature review, there seemed to be lack of research. Additionally, the genericfractions of base bitumens were quantified in order to assess the possible differences in physicalproperties.
2. Experimental section2.1. MaterialsStudied materials comprised base bitumens and cut-back bitumens, which were blends of basebitumen and fluxing agent. Base bitumens included three viscosity-graded (EN 12591) straight-run soft bitumens (denoted as V) and one penetration-graded (EN 12591) bitumen (denoted asB). Base bitumens are presented in Table 1. Cut-back bitumens were prepared by blending afore-mentioned four bitumens with bioflux (viscosity of c. 2 mm2/s at 60◦C), so that the blends wouldhave viscosity of 600 mm2/s at 60◦C calculated using Equation (1). Cut-back bitumens wereblended at 90–95◦C. Additionally, a traditional slow-curing cut-back bitumen used in Finland(designated as BL2K) was selected as a reference. BL2K was modified with fossil-fuel-derived
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 39
Table 1. Properties for base bitumens.
Capillary viscosity (mm2/s)
Temperature V15A V30A V60A B20A
60◦C 1420 2920 5660 36,700135◦C 37.3 52.5 71.6 171
Table 2. Compositions and properties of cut-back bitumens.
Composition Blend/ Blend/ Blend/
Base bitumen/ Solvent/ (base bit./ viscosity, viscosity, density,Cut-back viscosity, 60◦Ca viscosity, 60◦Ca solvent) 60◦Ca 135◦Ca 50◦Cblend (mm2/s) (mm2/s) (%/%) (mm2/s) (mm2/s) (kg/m3)
V15BF V15A 1420 Bioflux 2 94.5/5.5 590b/674 25.2 945.8V30BF V30A 2920 Bioflux 2 90.8/9.2 590b/587 24.1 945.2V60BF V60A 5660 Bioflux 2 88.5/11.5 640b/622 25.2 948.0B20BF B20A 36700 Bioflux 2 82.0/18.0 630b/646 24.7 945.6BL2K –c Kerosene + 86.0/7.0+7.0 551 25.0 942.2d
gas oil
aCapillary method.bCalculated.cClose to V60A (exact information was not available).d60◦C.
hydrocarbon flux (kerosene and gas oil, C6–C16 carbon atoms). Mixture of these crude oil dis-tillation fractions consists of both linear and branched alkanes, as well as naphthalene and itsderivatives (low-molecular-weight crystalline solids). None of the base bitumens or cut-backbitumens were polymer modified or had added wax. The compositions of the cut-back bitumenblends are presented in Table 2.
2.2. Generic fractionsThe generic fractions of the base bitumens were determined by thin-layer chromatographic methodwith flame-ionisation detector (IATROSCAN MK-6s). Bitumen samples were dissolved in chlo-roform and applied on chromarods. Saturates were eluted with n-heptane, aromatics with solutionof toluene (80%) and n-heptane (20%) and resins with solution of dichloromethane (95%) andmethanol (5%).
2.3. ViscosityViscosity of base bitumens and cut-back bitumens were determined with capillary method (EN12595 or 12596). Viscosity of cut-back bitumens were additionally measured in rotation witha Physica 301 rheometer equipped with peltier element on base plate and hood for accuratetemperature control. Shear speeds ranged from 0.001 1/s to 100 1/s (6 points per decade) with 10 smeasuring time and temperatures ranged from 20 to 100◦C starting from the lowest temperaturewith 10◦C increments. Measurement geometry for viscosity was cone-plate (50 mm in diameter).Samples were applied on measuring instrument at room temperature and trimmed at 40◦C. Sampleswere conditioned for 10 min before each test temperature.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
40 M. Simonen et al.
2.4. Complex shear modulus and phase angleComplex shear moduli and phase angles of all base bitumens and cut-back bitumens were exam-ined with the same rheometer (Physica 301) in oscillatory mode. Measuring geometry was parallelplates (25 mm in diameter). Frequencies for oscillation were 0.01–10 Hz (4 points per decade)and strains 0.1 (0.01 Hz) to 0.001 (10 Hz). Test temperatures ranged from −20 to 90◦C, and mea-surements were initiated from the lowest temperature with 10◦C increments. Conditioning timebefore each temperature was 10 min.
3. Results3.1. Generic fractionsThe generic fractions of the base bitumens are given in Table 3. The proportion of saturates andaromatics increases as the viscosity of bitumen decreases. Resin and asphaltene content increasesas the viscosity of bitumen increases. The composition of the soft bitumens deviates significantlyfrom the average composition of penetration-graded SHRP core asphalts (Jones, 1993). Lowcontent of asphaltenes and resins with high content of aromatics appears to be typical for the softbitumens V15A, V30A and V60A.
3.2. Viscosity of cut-back bitumensAll cut-backs were fairly Newtonian at shear stress levels above 0.1 Pa. Below 0.1 Pa testdata showed quite scattered points most likely due to limitations of test equipment. Figure 1demonstrates the shear susceptibility of B20BF cut-back.
The shear stress dependence of V15BF and V30BF at 20◦C was found to differ from that ofthe other cut-back bitumens. V60BF, B20BF and BL2K were rather Newtonian, whereas V15BFand V30BF showed strong non-Newtonian behaviour (see Figure 2). In addition to turning pointsin flow curves of V15BF and V30BF at 10 Pa, there was a minor decrease in viscosity of V60BFtoo. The flow curve of V15BF presented in Figure 2 implies to a network structure that graduallycollapses as the shear stress increases. Respectively, the shape of the flow curve for V30BF mayoriginate from the similar structure. V30BF showed distinctive shear thickening behaviour at20◦C. Polacco, Stastna, Vlachovicova, Biondi, and Zanzotto (2004) observed shear thinning andthickening from various polymer-modified bitumens.
Rotational viscosities of cut-back bitumens calculated as an average viscosity at shear ratesfrom 10 to 100 1/s are presented in Table 4. Rotational viscosities at 60◦C are slightly lowerthan that of capillary viscosities apart from BL2K (see Tables 2 and 4). The viscosities of cut-back bitumens differed greatly from each other at temperatures below 60◦C suggesting structuraldifferences in cut-back bitumens.
Table 3. Generic fractions of base bitumens and SHRP core asphalts.
Bitumen % saturates % aromatics % resins % asphaltenes
V15A 13.7 60.3 19.5 6.3V30A 10.8 56.8 23.7 8.5V60A 9.8 54.0 25.4 10.7B20A 5.4 52.5 26.9 15.2SHRP core asphalts (avg)a 2–13 (9.5) 25–45 (36.0) 26–51 (38.2) 4–23 (15.4)
aPenetrations between 51 and 160 1/10 mm.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 41
Figure 1. Flow curve of B20BF cut-back (20–100◦C).
Figure 2. Flow curves of biofluxed bitumens and cut-back bitumen at 20◦C.
Table 4. Rotational viscosities of cut-back bitumens.
Temperature (◦C) V15BF V30BF V60BF B20BF BL2K Unit
20 48,000 36,000 35,400 29,200 21,600 mPa s30 10,800 9000 9850 9000 689040 3430 3000 3340 3190 269050 1370 1200 1350 1300 123060 637 577 640 615 60970 330 311 340 329 32780 187 179 196 191 19290 116 112 123.0 120 125100 76.3 74.6 81.3 80.1 82.760 599 542 603 577 573 mm2/sa
aKinematic viscosities are calculated from dynamic viscosities using measured densities andconversion table in ASTM D 4311.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
42 M. Simonen et al.
Figure 3. Isochronal plots of phase angle for base bitumens at 1 Hz.
Figure 4. Isochronal plots of complex shear modulus for base bitumens at 1 Hz.
3.3. Complex shear moduli and phase angles of base bitumensThe anomalies in viscosity measurements at 20◦C were observed also in oscillatory measurements.The deviations in phase angle and complex shear modulus of V15BF and V30BF were prominentbetween 0 and 40◦C (see Figures 3 and 4). Airey (2002) discovered similar behaviour of phaseangles within ethylene vinyl acetate (EVA) polymer-modified bitumens, which were polymerphase dominant based on the basis of the studies with fluorescent microscopy. EVA representssemi-crystalline plastomers, which form a rigid network inside modified bitumen. Similar to thephase angles, the lower slope value (below 30◦C) of the complex modulus of V15BF resemblethe EVA-modified bitumens. The plateau region of phase angle for V15A bitumen ranged from0 to 30◦C. Airey concluded that a polymer network (EVA polymer network in his case) explainssuch a behaviour.
In this work no polymer-modified bitumen was used. However, in Figure 7 we present referencematerial of BL2K blend, with artificially introduced crystalline solids. Behaviour observed is
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 43
similar to that observed by Airey in EVA polymer-modified bitumens, yet it is assigned in thiswork to the contribution from crystalline structure similar or equal to that of waxes.
The shift of melting ranges between V15A to V15BF and V30A to V30BF is not constant.However, both cut-back bitumens express the same melting range (−10◦C to 20◦C). Waxespresent in bitumen, as any other fraction of components, are represented by a wide range ofcompounds. Alahmad, Al-Fariss, Abashar, and Etiouney (1995) proved that solubility of paraffinwaxes is dependable both on their composition and molecular weight of solvent used. A viableexplanation of observed phenomena (Figure 7) may originate in the ability of bioflux to solvateparticular fraction of crystalline solids naturally present in base bitumens. Figure 5 illustratesmaster curves constructed for the complex shear moduli of V15A (test temperatures −10 to60◦C) and B20A (20–90◦C). The master curve of B20A is rather uniform, but the curve of V15Aincludes divergences. Black diagrams are more sensitive to failures in TTSP principle. In Figure 6,V15A shows behaviour similar to waxy bitumens (Lesueur et al., 1996; Soenen et al., 2006) orbitumens modified with EVA copolymer (Airey, 2002). Violations against Ferry’s criteria forTTSP principle are obvious for the softest bitumens studied.
Figure 5. Master curves of V15A and B20A (Tref = 20◦C).
Figure 6. Black diagrams of V15A and B20A.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
44 M. Simonen et al.
3.4. Complex shear moduli and phase angles of cut-back bitumensThe rheological properties of base bitumens were evident in the properties of cut-back bitumens.Figure 7 shows that the phase angle of V15BF remained unaffected at temperatures between −10and 10◦C. The behaviour of V30BF and BL2K was alike. The plateau region of the phase anglefor V15BF is narrower and situated at a lower temperature than the plateau region for unmodifiedV15A bitumen.
The viscosities of cut-back bitumens differed remarkably below 60◦C. The same phenomenonbecame apparent in oscillatory measurements. Figure 8 shows great divergences between cut-back bitumens. The stiffness of V15BF increased rapidly as the temperature decreased from 30 to10◦C. The complex shear modulus of BL2K decreased slightly above 5◦C. At −20◦C the complexmodulus of V15BF (5,890,000 Pa) was over 10 times larger than that of B20BF (494,000 Pa).
Figure 7. Isochronal plots of phase angle for biofluxed bitumens and cut-back bitumen at 1 Hz.
Figure 8. Isochronal plots of complex shear modulus for biofluxed bitumens and cut-back bitumen at1 Hz.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 45
4. DiscussionThe composition and rheological characteristics of both the base bitumens and cut-back bitumensdiffered significantly from each other. The behaviour of the base bitumens V15A and V30A andcut-back bitumens made from them resembled the rheological behaviour observed for waxy orEVA-modified bitumens. Waxes and EVA copolymers crystallise within bitumen forming rigidthree-dimensional network. On the basis of the observed similarities the findings of this studymay be explained by crystalline compounds naturally occurring in bitumen.
A closer examination on literature of waxes found in bitumens supports the presence of waxesin the studied materials. The work by Claudy, Letoffe, King, and Planche (1992) identified waxcrystallisation/precipitation and melting/dissolution phenomena in the paving grade bitumensat temperatures of 25 to 80◦C by studying the correlation between DSC and thermomicroscopy.They also noticed “unique rheological behaviour atypical of conventional viscoelastic fluids”caused by highly crystallisable fractions. Musser and Kilpatrick (1998) reported that peak melt-ing temperatures for waxes isolated from various crude oils lay between 30 and 57◦C. Lu andRedelius (2006) separated wax from six bitumens and found peak melting temperatures rang-ing from 41 to 64◦C (upon heating) and peak crystallisation temperatures between 36 and 57◦C(upon cooling). Lu, Langton, Olofsson, and Redelius (2005) research with DSC showed thatwaxes within penetration grade bitumens melt out at high temperatures (63–92◦C). The tem-peratures, where wax crystallisation starts in bitumen, are typically considerably lower than themelting temperatures. Lu et al. (2005) found starting temperatures for wax crystallisation between18 and 46◦C.
The above-mentioned temperature ranges were equal to the temperatures at which divergenceswere observed in viscosities, complex shear moduli and phase angles of the studied materials. Afterthe viscosities of the base bitumens were lowered with bioflux, melting of crystalline structuresoccurred in lower temperatures. Presumably less viscous medium of biofluxed bitumens allowedcrystals to melt more readily than the base bitumens. Lu et al. (2005) concluded that crystallisationdepends strongly on time and temperature. At low temperatures (highly viscous medium), Lu et al.discovered no wax crystals in two bitumens even after 24 h.
Wax contents of the studied bitumens were not examined during this research; Lu and Redelius(2007) suggest that, from low-temperature performance point of view, it is more important to definemelt characteristics rather than ultimate wax content. Remember that the paraffin wax contentdepends on characterisation technique employed, and that neither DSC nor the two methodsproposed in EN 12606-1 (distillation and extraction) provide ultimate value (Lu & Redelius,2007), the paraffin wax content of 2.5% in V15A and 1.9% in B20A as typically reported (EN12606-1) were incorporated into further interpretation of our results. The higher wax content ofV15A may partly explain the differences between V15A and B20A.
The effect of the composition on wax crystallisation in crude oils has been widely examined.Especially asphaltenes and the ratio of asphaltenes to wax have gained interest. The effect ofasphaltenes has proven to be two-fold in crude oils (Tinsley, Jahnke, Dettman, et al., 2009)meaning that asphaltenes may either inhibit crystallisation and networking (Chanda et al., 1998;Tinsley, Jahnke, Adamson, et al., 2009; Tinsley, Jahnke, Dettman, et al., 2009) or act as nucleationsites and thus increasing flocculation (del Carmen García, 2000; del Carmen García & Carbognani,2001). One of the major differences between V15A and B20A is the amount of asphaltenes. Lowasphaltene content and higher wax content of V15A probably explains the differences of V15Aand V15BF from B20A and B20BF. The other base bitumens and cut-back bitumens are situatedbetween these extreme materials. As the asphaltene content in the other base bitumens increased,the rheological characteristics were approaching B20A having the highest asphaltene content.
Because low-polar fractions (saturates and aromatics) dominate the low-temperature behaviourof bitumens, addition of the low-polar and low-molecular-weight alkanes (bioflux) affected
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
46 M. Simonen et al.
particularly the low-temperature consistencies. Thus the overall rheological behaviour of cut-backbitumens may be attributed to differences in wax to asphaltene ratio and the bioflux content.
The temperature history has a significant effect on the structure and rheological properties ofbituminous binders (Claudy et al., 1992; Masson, Polomark, & Collins, 2002; Planche, Claudy,Létoffé, & Martin, 1998; Soenen et al., 2006). In this study, the rheological measurements wereinitiated from the lowest test temperature after 10 min of conditioning. Because crystallisationand melting occur at different temperatures and are time dependent, the temperature history ofthe samples affected the measured properties.
This research exposed some major differences between the various biofluxed bitumens. How-ever, additional research on the aging behaviour of biofluxed bitumens and on the performanceof the asphalt concrete mixtures made of biofluxed bitumens is needed before utilising them indifferent applications.
5. ConclusionsThe composition of both base bitumens and cut-back bitumens affected remarkably theirrheological characteristics. The results of this study may be concluded as follows:
The softest bitumens (V15A and V30A) proved to be rheologically complex materials exhibit-ing crystallisation in the temperature range of actual use. The crystalline network increased boththe elasticity and overall stiffness of V15A and V30A bitumens. The behaviour of B20A, thehardest bitumen studied resembled most the traditional neat bitumens referred in literature. Thecrystallisation observed in rheological measurements was addressed to the wax naturally presentin bitumen. Further research warrants verification of crystallisation by DSC testing, as well asfurther investigation on wax fraction solubility in fluxes used.
The asphaltene content presumably affected crystallisation. B20A with relatively high asphal-tene content exhibited no wax crystallisation. Respectively, V15A with low asphaltene contentexhibited strong crystallisation phenomenon.
The addition of bioflux shifted the melting of crystals to the lower temperatures and narrowed themelting range. Thus, the wax crystallisation and melting temperatures depended on the viscosityof the bitumen blends, which was also supported by the literature.
Neither physical nor chemical properties of bioflux were the subject of this study, as allincorporated bitumen characterisation techniques were not suitable for ultimate analysis of low-molecular-weight hydrocarbons. However, we are aware of potential contribution of biofluxproperties to the results obtained on the cut-back bitumens and we wish to pursuit further researchof this environmentally favourable solvent by means of SARA analysis, DSC and viscometry, aswell as its wax-solving properties.
Nevertheless, bioflux affected particularly the low-temperature properties of cut-back bitumens.Low viscosity alkanes reduced the stiffness remarkably under 30◦C, which may be desirable forbituminous binders utilised in stockpile patching materials.
Cut-back bitumens obtained with bioflux expressed similar characteristics to conventionallyused (BL2K), while providing increased work safety (flash point of kerosene and bioflux arebelow and above 60◦C, respectively).
AcknowledgementsNynas Oy is acknowledged for financial support. The authors thank the personnel of Neste Oil’s TechnologyCenter in Porvoo, Finland for carrying out extensive binder testing. Also, technical assistance provided bygraduate research assistant M.Sc. Michalina Makowska from Aalto University is greatly appreciated. Shecontributed to the interpretation of test results in terms of chemistry.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
Road Materials and Pavement Design 47
ReferencesAirey, G.D. (2002). Rheological evaluation of ethylene vinyl acetate polymer modified bitumens.
Construction and Building Materials, 16, 473–487.Airey, G.D., & Rahimzadeh, B. (2004). Combined bituminous binder and mixture linear rheological
properties. Construction and Building Materials, 18, 535–548.Alahmad, M., Al-Fariss, T.F., Abashar, M.E., & Etiouney, H.M. (1995). An empirical correlation for the
solubility of paraffin waxes in base oils. Journal of King Abdulaziz University Engineering Sciences, 7,81–92.
Anderson, D.A., Christensen, D.W., Bahia, H.U., Dongre, R., Shrama, M.G., Antle, C.E., & Button, J.(1994). Binder characterization and evaluation – Volume 3 (SHRP-A-369).
del Carmen García, M. (2000). Crude oil wax crystallization. The effect of heavy n-paraffins and flocculatedasphaltenes. Energy Fuels, 14, 1043–1048.
del Carmen García, M., & Carbognani, L. (2001). Asphaltene–paraffin structural interactions. Effect on crudeoil stability. Energy Fuels, 15, 1021–1027.
Centeno, G., Sánchez-Reyna, G., Ancheyta, J., Muñoz, J.A.D., & Cardona, N. (2011). Testing various mixingrules for calculation of viscosity of petroleum blends. Fuel, 90(12), 3561–3570.
Chanda, D., Sarmah, A., Borthakur, A., Rao, K.V., Subrahmanyam, B., & Das, H.C. (1998). Combinedeffect of asphaltenes and flow improvers on the rheological behaviour of Indian waxy crude oil. Fuel,77, 1163–1167.
Claudy, P., Letoffe, J.M., King, G.N., & Planche, J.P. (1992). Characterization of asphalt cements by ther-momicroscopy and differential scanning calorimetry: Correlation to classic physical properties. FuelScience and Technology International, 10(4–6), 735–765.
Claudy, P., Letoffe, J.M., King, G.N., Planche, J.P., & Brule, B. (1991). Characterization of paving asphaltsby differential scanning calorimetry. Fuel Science and Technology International, 9(1), 71–92.
Davison, R.R., Bullin, J.A., Glover, C.J., Chaffin, J.M., Peterson, G.D., Lunsford, K.M., …Ferry, M.A.(1994). Verification of an asphalt aging test and development of superior recycling agents and asphalts(FHWA/TX-94/1314-1F).
Domke, C.H., Davison, R.R., & Glover, C.J. (1999). Effect of asphaltenes on SHRP Superpave specifications.Energy Fuels, 13, 340–345.
Doraiswamy, D. (2002). The origins of rheology: A short historical excursion. Rheological Bulletin, 71, 1–9.Epps, J.A., Little, D.N., Holmgreen, R.J., & Terrel, R.L. (1980). Guidelines for recycling pavement materials
(Report, 224).Ferry, J.D. (1970). Viscoelastic properties of polymers (2nd ed., pp. 292–351). New York, NY: John Wiley.Griffin, R.L., Simpson, W.C., & Miles, T.K. (1959). Influence of composition of paving asphalt on viscosity,
viscosity-temperature susceptibility, and durability. Journal of Chemical & Engineering Data, 4, 349–354.
IPCC. (2001). Atmospheric chemistry and greenhouse gases. In J.T. Houghton, Y. Ding, D.J. Griggs, M.Noguer, P.J. van der Linden, X. Dai, K. Maskell, & C.A. Johnson (Eds.), Climate Change 2001: The sci-entific basis. Contribution of Working Group I to the Third Assessment Report of the IntergovernmentalPanel on Climate Change (pp. 239–288). Cambridge: Cambridge University Press.
Jewell, D.M., Albaugh, E.W., Davis, B.E., & Ruberto, R.G. (1974). Integration of chromatographic andspectroscopic techniques for the characterization of residual oils. Industrial and Engineering ChemistryFundamentals, 13, 278–282.
Jones, D.R. (1993). SHRP materials reference library: Asphalt cements: A concise data compilation (SHRP-A-645).
Lesueur, D. (2009). The colloidal structure of bitumen: Consequences on the rheology and on the mechanismsof bitumen modification. Advances in Colloid and Interface Science, 145, 42–82.
Lesueur, D., Gerard, J.F., Claudy, P., Letoffe, J.M., Planche, J.P., & Martin, D. (1996). A structure-relatedmodel to describe asphalt linear viscoelasticity. Journal of Rheology, 40, 813–836.
Loeber, L., Muller, G., Morel, J., & Sutton, O. (1998). Bitumen in colloid science: A chemical, structuraland rheological approach. Fuel, 77, 1443–1450.
Lu, X., & Isacsson, U. (2002). Effect of ageing on bitumen chemistry and rheology. Construction andBuilding Materials, 16, 15–22.
Lu, X., Langton, M., Olofsson, P., & Redelius, P. (2005). Wax morphology in bitumen. Journal of MaterialsScience, 40, 1893–1900.
Lu, X., & Redelius, P. (2006). Compositional and structural characterization of waxes isolated from bitumens.Energy Fuels, 20(2), 653–660.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
48 M. Simonen et al.
Lu, X., & Redelius, P. (2007). Effect of bitumen wax on asphalt mixture performance. Construction andBuilding Materials, 21(11), 1961–1970.
Masson, J., & Polomark, G.M. (2001). Bitumen microstructure by modulated differential scanningcalorimetry. Thermochimica Acta, 374, 105–114.
Masson, J., Polomark, G.M., & Collins, P. (2002). Time-dependent microstructure of bitumen and its fractionsby modulated differential scanning calorimetry. Energy Fuels, 16, 470–476.
Michalica, P., Kazatchkov, I.B., Stastna, J., & Zanzotto, L. (2008). Relationship between chemical andrheological properties of two asphalts of different origins. Fuel, 87, 3247–3253.
Musser, B.J., & Kilpatrick, P.K. (1998). Molecular characterization of wax isolated from a variety of crudeoils. Energy Fuels, 12, 715–725.
Petersen, J.C., Robertson, R.E., Branthaver, J.F., Harnsberger, P.M., Duvall, J.J., Kim, S.S., … Bahia, H.U.(1994). Binder characterization and evaluation – volume 1 (SHRP-A-367).
Planche, J.P., Claudy, P., Létoffé, J.M., & Martin, D. (1998). Using thermal analysis methods to betterunderstand asphalt rheology. Thermochimica Acta, 324, 223–227.
Polacco, G., Stastna, J., Vlachovicova, Z., Biondi, D., & Zanzotto, L. (2004). Temporary networks inpolymer-modified asphalts. Polymer Engineering & Science, 44, 2185–2193.
Redelius, P. (2004). Bitumen solubility model using Hansen solubility parameter. Energy Fuels, 18, 1087–1092.
da Silva, L.S., de Camargo Forte, M.M., de Alencastro Vignol, L., & Cardozo, N.S.M. (2004). Study ofrheological properties of pure and polymer-modified Brazilian asphalt binders. Journal of MaterialsScience, 39, 539–546.
Soenen, H., De Visscher, J., Vanelstraete, A., & Redelius, P. (2006). Influence of thermal history onrheological properties of various bitumen. Rheologica Acta, 45, 729–739.
Suomen Standardisoimisliitto (SFS). (2005). Bitumen and bituminous binders. Determination of complexshear modulus and phase angle – dynamic shear rheometer (DSR) (SFS-EN 14770).
Tinsley, J.F., Jahnke, J.P., Adamson, D.H., Guo, X., Amin, D., Kriegel, R., …Prud’home, R.K. (2009). Waxygels with asphaltenes 2: Use of wax control polymers. Energy Fuels, 23, 2065–2074.
Tinsley, J.F., Jahnke, J.P., Dettman, H.D., & Prud’home, R.K. (2009). Waxy gels with asphaltenes 1:Characterization of precipitation, gelation, yield stress, and morphology. Energy Fuels, 23, 2056–2064.
Valtonen, J., Pellinen, T., & Blomberg, T. (2010, August). Development of environmentally friendlycold patching compound. International Society of Asphalt Pavements (ISAP), The 11th InternationalConference of Asphalt Pavements, Nagoya, Japan.
Dow
nloa
ded
by [
McG
ill U
nive
rsity
Lib
rary
] at
22:
01 1
2 M
arch
201
3
