Midrange Temperature Rheological Properties of Warm Asphalt Binders

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Midrange Temperature Rheological Propertiesof Warm Asphalt Binders

Szabolcs Biro1; Tejash Gandhi2; and Serji Amirkhanian, M.ASCE3

Abstract: With increasing concerns of global warming and increasing emissions, the asphalt industry is making a constant effort to lowerits emissions by reducing the mixing and compaction temperatures of the asphalt mixture without affecting the properties of the mix.Several proprietary chemicals are available in the industry that can help reduce the mixing and compaction temperatures. A significantreduction of required heat can be achieved in most cases. Several studies have been conducted evaluating the properties of the warm mixasphalt; however, properties of the binders containing these chemicals have not been studied in great detail. Warm asphalts were producedusing two of the available processes utilizing five different asphalt binder sources, and some rheological tests were conducted �dynamicshear rheometer and viscosity�. The results indicated that binders containing the inorganic additive Aspha-Min �Eurovia, France� under-went minor or no changes compared to the base binders in terms of flow properties, stiffness, and response to creep. However, the flowof binders with the additive Sasobit �Sasol Wax, Germany�, which consists of aliphatic hydrocarbons, changed from Newtonian to shearthinning at 60°C, and the viscosity of the binder at 60°C increased. Sasobit also improved the stiffness and penetration resistance of thebase binders, and binders with Sasobit had significantly lower permanent deformations after repeated creep-recovery tests compared to thebase binders.

DOI: 10.1061/�ASCE�0899-1561�2009�21:7�316�

CE Database subject headings: Rheology; Asphalts; Binders, materials; Temperature effects.

Introduction

Warm asphalt has been gaining increasing popularity in recentyears. The asphalt industry has been experimenting with warmand cold asphalt for decades now in order to reduce energy re-quirements and for environmental benefits. However, in manycases, most of the cold products have been inferior to hot-mixasphalt �HMA�. Emulsion binders usually result in higher airvoids, require longer curing times, and tend to work only withopen- and coarse-graded mixtures. Cutback bitumen also has en-vironmental concerns due to the volatile chemicals and requireslonger curing times. Foamed bitumen does not require long cur-ing times, but only coats fine aggregate well �Rajagopal 2004�,and is more suitable for recycling applications. Another problemwith these methods is that the extra costs are not offset by thesavings in energy.

The Bitumen Forum of Germany, in 1997, started investigatingmethods of lowering emissions, and “warm mix technology” wasone of the avenues they pursued. Typically, the warm asphaltmixtures are produced and compacted at temperatures ranging

1Postdoctoral Fellow, Dept. of Civil Engineering, Clemson Univ.,Clemson, SC 29631. E-mail: [email protected]

2Graduate Research Assistant, Dept. of Civil Engineering, ClemsonUniv., Clemson, SC 29631 �corresponding author�. E-mail: [email protected]

3Professor, Dept. of Civil Engineering, Clemson Univ., Clemson, SC29631. E-mail: [email protected]

Note. This manuscript was submitted on July 11, 2007; approved onJanuary 15, 2009; published online on June 15, 2009. Discussion periodopen until December 1, 2009; separate discussions must be submitted forindividual papers. This paper is part of the Journal of Materials in CivilEngineering, Vol. 21, No. 7, July 1, 2009. ©ASCE, ISSN 0899-1561/
2009/7-316–323/$25.00.
316 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY 2

J. Mater. Civ. Eng. 200

from 90 to 130°C �Gandhi 2008�. The European interest in re-ducing the emission of greenhouse gases was mainly as a result ofthe Kyoto agreement. Warm mix asphalt �WMA� was introducedto the United States when the National Asphalt Pavement Asso-ciation �NAPA� sponsored an industry-scanning tour to Europefor the asphalt paving contractors in 2002. In 2003, NAPA, theFederal Highway Administration �FHwA�, and the National Cen-ter for Asphalt Technology �NCAT� convened a meeting to ex-plore the potential of the technologies in the United States, andthe three technologies were presented at the NAPA convention inSan Diego. The “World of Asphalt,” 2004, featured a demonstra-tion project on WMA, and since then, the major warm asphaltadditive companies have carried out several demonstrationprojects in the United States.

Apart from the obvious advantages such as reduced fuel con-sumption and reduced emissions in the plant, there are severalother advantages of using warm asphalt such as longer paving“seasons,” longer hauling distances, reduced wear and tear of theplants, reduced aging of binders, reduced oxidative hardening ofbinders and thus reduced cracking in the pavements, ability ofopening the site to traffic sooner, etc. �Hurley and Prowell2006a,b�. With the availability of several proprietary chemicalsand processes to produce warm asphalt, it is now possible toproduce warm asphalt without affecting the properties of the mix.Some of the most common processes/chemicals available todayare described below.

Aspha-Min �Eurovia, France�, is a sodium–aluminum–silicate,which is hydrothermally crystallized as a very fine powder. Itcontains about 21% crystalline water by weight. Aspha-Min isadded to the mixture at a rate of 0.3% by weight of the mixture.By adding it to the mixture at the same time as the binder, a veryfine water spray is created as all the crystalline water is released,which causes volume expansion in the binder, thereby increasing
the workability and compactibility of the mixture at lower tem-
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peratures. It has been reported, by the manufacturer, that a reduc-tion of about 40–50°F has been observed �Eurovia Services2007�.

Evotherm �MeadWestvaco, USA� uses a chemical additivetechnology and a “dispersed asphalt technology,” delivery system.The producer states that by using this technology a unique chem-istry customized for aggregate compatibility is delivered into adispersed asphalt phase �emulsion�. During production, the as-phalt emulsion with the Evotherm chemical package is used inplace of the traditional asphalt binder. The emulsion is then mixedwith the aggregate in the HMA plant. The manufacturer reportsthat this chemistry provides better aggregate coating, workability,adhesion, and improved compaction with no change in materialsor job mix formula required. In addition, they report that fieldtesting has demonstrated a 100°F reduction in production tem-peratures �MeadWestvaco 2007�.

Sasobit �Sasol Wax, Germany� is a long chain aliphatic hydro-carbon �chain lengths of 40–115 carbon atoms� obtained fromcoal gasification using the Fischer–Tropsch process. The meltingpoint of Sasobit is around 185–240°F. Sasobit forms a homoge-neous solution with the base binder on stirring, and produces amarked reduction in the binder’s viscosity. Reductions of about50–90°F in the mixing and handling temperatures of the mixturehave been reported by the producer. After crystallization, Sasobitforms a lattice structure in the binder, which is the basis of thestructural stability of the binder containing Sasobit �Sasol Wax2007�.

WAM-Foam �Shell, Norway� is formed using two separatebinder components in the mixing stage. A soft binder is mixedwith the aggregate in the first stage at approximately 230°F toachieve full aggregate coverage. The hard binder component ismixed in a second stage into the precoated aggregates in the formof foam. The hard binder foam combines with the soft binder toachieve the final required composition and properties of thebinder. The success of WAM-Foam depends on careful selectionof the soft and hard components. The initial coating of the aggre-gate in the first mixing stage is vital to prevent water from reach-ing the binder and aggregate interface �Federal HighwayAdministration 2006�.

With increasing awareness of the warm asphalt technology inthe asphalt industry, several properties of warm asphalt should beinvestigated. While several studies have been conducted to studythe performance of warm asphalt mixtures �Hurley and Prowell

Table 1. Properties of Virgin Binders

Property Binder 1 B

Original binderViscosity Pa s �135°C� 0.626 0

G* /sin �, kPa �64°C� 1.801 1

Rolling thin-film oven residueMass loss, % �163°C� −0.24 −

G* /sin �, kPa �64°C� 4.608 2

Pressure-aging vessel residue

G* sin �, kPa �25°C� 2420

Stiffness �60�, MPa �−12°C� 129

m-value �60� �−12°C� 0.345

Performance grade 64–22 6

Missing temperaturea, °C 163–170 15

Compaction temperaturea, °C 150–155 13aInformation provided by supplier.

2006a,b; Barthel et al. 2007; Hurley and Prowell 2005a,b�, the

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properties of the binder containing the warm asphalt additiveshave not been studied in great detail. This paper presents theresults of some rheological tests conducted on warm asphalt bind-ers.

Materials and Experimental Procedures

Five different binders were selected for this study. The first binderwas from a Venezuelan source, the second was from differentsources blended together, the third was from Texas, the fourth wasfrom Canada, and the fifth was from the Rocky Mountains. Allthe binders were of PG 64-22 grade, and their properties areshown in Table 1. Warm asphalt was prepared using two of theavailable commercial products. Process 1 involved the addition ofAspha-Min, a chemical powder at a specified concentration �0.3%by weight of mixture—a binder content of 6% was assumed, andthe entire additive was added to the binder� followed by mixingwith a stirrer to disperse the powder throughout the binder. Pro-cess 2 involved addition of Sasobit, pellets at specified concen-tration �1.5% by weight of the binder� followed by mixing for5 min in a shear mixer to achieve consistent mixing. The addi-tives were added to the binders at 120°C, which is approximatelythe mixing temperature for warm asphalt mixtures containingthese binders.

Following the preparation of the warm asphalt binders, rheo-logical tests such as viscous flow measurements, frequencysweep, creep, creep recovery, and multiple creep-recovery tests,at 60°C were conducted using a Bohlin dynamic shear rheometer�DSR� with a 25 mm diameter plate–plate geometry, and 1 mmgap. Additionally, a temperature sweep test was performed be-tween temperatures of 25 and 80°C at a frequency of 1.59 Hz.The testing plan is shown in Fig. 1.

Gel permeation chromatography �GPC� analysis was also con-ducted to identify any changes in the molecular size distributionsin the five binders after the addition of the warm asphalt addi-tives. GPC is a well-known technique for characterizing the mo-lecular size distribution of asphalt binders �Kim et al. 2006�.Waters GPC equipment with a computerized software was usedfor the chromatographic analysis of the binders. A differentialrefractive meter �Waters 410� was used as a detector. A series oftwo columns �Waters HR 4E and Waters HR 3� was used to

Binder 3 Binder 4 Binder 5

0.457 0.453 0.420

1.315 1.321 1.284

−0.01 −0.06 −0.14

3.780 2.93 3.27

1704 1400 2565

117 108 132

0.320 0.326 0.335

64–22 64–22 64–22

— — —

— — —

inder 2

.405

.207

0.02

.815

2970

183

0.311

4–22

0–155

9–144

separate the constituents of the binder by molecular size. The

OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY 2009 / 317

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columns were maintained at 35°C in order to be able to test thesamples at a constant temperature. Tetrahydrofurane �THF� wasused as the mobile phase, flowing at a rate of 1 ml /min and adilution of 400:1 �solvent:binder�. Each test specimen was pre-pared by weighing 0.006 to 0.008 g of binder into a 4 ml emptyvial. The appropriate amount of THF was added to the vial, andthe vial was sealed and agitated so that the binder was completelydissolved in the solvent. The binder solvent mixture was thentransferred to a 5 ml syringe, and filtered through a 0.45 �m filterinto a clean vial. Seventy-five microliters of the filtered bindersolvent mixture was injected into the GPC. One vial was preparedfor each binder, and three chromatograms were obtained fromeach vial.

Binder 2(64 -22)

Wa

Control As

Rheo

Viscosity / FlowCurves

Creep@ 10 Pa Creep Recovery

Creep Recovery @ 3 Pa Creep Recovery @ 10 Pa

BBinder 1(64 -22)

Fig. 1. Ex

0

20

40

60

80

Binder 1 Binder 2 Binder 3 Binder 4 Binder 5

%LMS

Virgin Binder Asphamin Sasobit

0

20

40

60

80

Binder 1 Binder 2

SMS%

Virgin Bind

(a)

Fig. 2. GPC analysis of the binders



Results

Gel Permeation Chromatogram

The percentages of large molecular sizes �LMS�, medium mo-lecular size �MMS� and the small molecular size �SMS� of thefive binders with and without the additives are shown in Fig. 2.Many studies indicate that the LMS of the binder has a goodcorrelation with the asphalt mixture properties than other sizes�Al-Adulwahhab et al. 1999; Jennings 1980; Kim and Burati1993; Kim et al. 1993; Price 1988�. From the GPC analysis it wasobserved that the addition of Aspha-Min did not have any signifi-cant effect on the LMS of the base binders. When Sasobit was

Binder 4(64 -22)

alt

® Sasobit®(S)

ests

Frequency Sweeped Creep Recovery

ep Recovery @ 50 Pa

Temperature Sweep

Binder 5(64 -22)

ental plan

0

20

40

60

80

Binder 1 Binder 2 Binder 3 Binder 4 Binder 5Virgin Binder Asphamin Sasobit

er 3 Binder 4 Binder 5

sphamin Sasobit

(b)

)

LMS; �b� % MMS; and �c� % SMS

Binder

rm Asph

pha-Min(A)

logical T

Repeat

Cre

inder 3(64 -22)

perim

%MMS

Bind

er A

(c

�a� %

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added to the binders, there was no significant effect on the LMSof binders with the exception of Binder 1, where the LMS de-creased significantly. Noureldin �Noureldin 1982� reported thatlow percentages of LMS could increase the temperature suscep-tibility of the mixtures, making them more prone to rutting.

Since the warm mix additives were developed to reduce themixing and compaction temperatures of asphalt mixtures, theywould most significantly affect the flow properties of the asphaltbinder. All the rheological measurements were undertaken at60°C, within the linear viscoelastic region of the binders, there-fore the stress and strain relationships were influenced by thefrequency of loading only and not by the magnitude of thestresses and strains �Ferry 1980�. The results of the rheological

Shear rate, sec-10.001 0.01 0.1 1 10

Viscosity( η),Pas

102

103

104

100

101

102

103

104Binder 1 (η)Binder 1 + A (η)Binder 1 + S (η)Binder 1 (σ)Binder 1 + A (σ)Binder 1 + S (σ)

Shear rate, sec-10.001 0.01 0.1 1 10

Viscosity( η),Pas

102

103

104

100

101

102

103


Shear

0.001 0.01

Viscosity,Pas

102

103

104 Binder 5Binder 5 + ABinder 5 + SBinder 5Binder 5 + ABinder 5 + S

(a)

(c)

(

Fig. 3. Flow and viscosity curves affected by Aspha-Min and Sasobi

tests are discussed below.

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Flow

Fig. 3 shows the relationship of shear stress and viscosity to theshear rate for the five binders, with and without the warm mixadditives. All five virgin binders seem to follow Newtonian flowat 60°C, as the viscosities are independent of the shear rates. Theaddition of Aspha-Min also does not seem to influence the flow ofthe binders. However, the addition of Sasobit to these five bindersinfluences the flow behavior of the binders. When Sasobit wasadded to the binders, the viscosity decreased with increase inshear rate, thereby exhibiting a shear thinning flow at 60°C.

It can also be seen from the graphs that the addition of thewarm mix additives increased the viscosities of the five binders at

Shear rate, sec-10.001 0.01 0.1 1 10

102

103

104

Shearstress( σ),Pa

100

101

102

103


Shear rate, sec-10.001 0.01 0.1 1 10

102

103

104

Shearstress( σ),Pa

100

101

102

103


c-11 10

Shearstress,Pa

100

101

102

103

104

(b)

(d)

Binder 1; �b� Binder 2; �c� Binder 3; �d� Binder 4; and �e� Binder 5

Shearstress( σ),Pa

Viscosity( η),Pas

Shearstress( σ),Pa

Viscosity( η),Pas

rate, se

0.1

e)

t—�a�

60°C. The addition of Sasobit especially increases the viscosity


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of the binders more than Aspha-Min. In another study �Gandhiand Amirkhanian 2007�, it was observed that adding Sasobit tothe binder reduced the viscosity of the binder at high temperatures�120 and 135°C�. This means that Sasobit decreases the viscosityof the binders at higher temperatures, but increases the viscosityat midrange temperatures, which makes it more workable at hightemperatures, and stiff and, therefore, more resistant to penetra-tion and rutting at midrange temperatures. While the increase inthe viscosity due to Aspha-Min could be because of the fillingeffect of the additive, Sasobit is a wax, which recrystallizes in thebinder on cooling, thereby increasing the viscosity of the binder atlower temperatures �Edwards et al. 2006�.

Frequency Sweep Tests

For the frequency sweep tests, four decades of frequencies �0.01–0.1, 0.1–1, 1–10, and 10–100� were run at the lowest possiblestrain. Fig. 4 shows the elastic and viscous moduli for binders 1and 2 as a function of frequency of loading. Other binders fol-lowed trends similar to Binder 1. Typically, a frequency of1.59 Hz simulates the shearing action corresponding to trafficspeed of about 55 mph �Roberts et al. 1996�.

From the graphs, it can be seen that as the frequency increases,the difference between the viscous and elastic moduli decreasesfor all the binders. In the case of Binder 2 with Sasobit, the elasticmodulus is more than or equal to the viscous modulus beyondfrequencies of 1 Hz. This suggests that the binder will undergoless permanent deformation at these frequencies, and therefore themixture will be less prone to rutting at higher traffic speeds com-pared to the other binders. Also, when Sasobit was added to thesebinders, it produced the highest elastic and viscous components at

Fig. 4. Frequency dependence of elastic a

Time, s0 50 100 150 200 250 300

Compliance,1/Pa

0.0

0.5

1.0

1.5

2.0Binder 1Binder 1 + ABinder 1 + S

(a)

Fig. 5. Creep curves affected by Aspha



any given frequency, suggesting that Sasobit improves the stiff-ness of the binder when compared to the base binders, and bind-ers containing Aspha-Min at any given frequency.

Creep

Creep is defined as the slow deformation of a material measuredunder a constant stress. In the creep test, a fixed shear stress isapplied to the sample, and the resultant strain is monitored for apredetermined amount of time. In this project, a shear stress of10 Pa was applied, and the strain was measured for a period of300 s.

Since the actual change of strain depends on the applied stress,Compliance �J� is used as a measure of creep rather than strain.The compliance is the ratio of strain to the applied stress. Thatway, samples tested at different stress levels can be compared. Ahigher value of compliance at any given stress level and instanceimplies higher deformation and stiffness of the binder. Fig. 5shows the compliances for binders 1 and 2 used in this projectwith and without the warm asphalt additives. The other bindersfollowed similar trends. It can be seen that binders with Sasobithave lower compliance values implying that Sasobit improves thestiffness of the binders at midrange temperatures.

When Aspha-Min was added to binders, the compliance valueswere lowered compared to the base binder; whereas the additionof Aspha-Min to Binder 3 had increased compliance values com-pared to the base binder. Since Aspha-Min acts only as mineralfiller after the initial foaming, the stiffening effect of the additiveseems to be binder dependent, and may not always act to stiffenthe binder.

cous moduli—�a� Binder 1; �b� Binder 2

Time, s0 50 100 150 200 250 300

Compliance,1/Pa

0.0

0.5

1.0

1.5


)

nd Sasobit—�a� Binder 1; �b� Binder 2

nd vis

(b

-Min a

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Creep Recovery

In a creep-recovery test, the recovery from a creep loading isdetermined. This gives an idea of the permanent deformation thatthe binder will undergo. In this test, a fixed shear stress is appliedto the sample, and the resultant strain is monitored as a functionof time. After a predetermined period of time, the stress is re-moved, and the strain is further monitored. Creep-recovery testswere run at three different stresses in this project, 3 Pa �loadingfor 100 and 600 s recovery�, 10 Pa �loading for 20 and 600 srecovery�, and 50 Pa �loading for 1 and 300 s recovery�. Thesestresses represent the low, medium, and high stress levels on apavement. Stresses lower than 3 Pa could not be applied due tothe limitations of the DSR used. Fig. 6 shows the creep-recoverycurves for Binder 1 with and without the warm asphalt additivesat different stress levels. Other binders followed similar trends.From the curves, it can be seen that for most of the cases, theaddition of Sasobit has the lowest maximum deformation. Also,after the stress is removed, binders with Sasobit show the leastpermanent deformation. However, in some cases, especially athigh stress values �50 Pa�, the binders had not yet attained thesteady state viscous flow, and thus different results may have beenobtained if the strain was measured for a longer duration after thestress was removed.

Repeated Creep Recovery

The repeated creep-recovery test was conducted on all the fivebinders with and without the warm asphalt additives. The re-

Time, s0 200 400 600

Compliance,1/Pa

0.0

0.1

0.2

0.3

0.4

0.5


0 50 10

Compliance,1/Pa

0.000

0.001

0.002

0.003

0.004

0.005

0.006

(a)

Fig. 6. Creep-recovery curves for Aspha-Min and S

peated creep-recovery test simulates field conditions better as it

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applies a stress for a short duration of time and then leaving thematerial to recover for a longer duration of time, and repeats thisseveral times. This in a way simulates vehicles passing on a pave-ment �Binard et al. 2004�. The test consisted of 52 cycles of load-ing with a stress of 10 Pa for 1 s, and recovery for 9 s. Thesetesting parameters were based on the suggestions from theNCHRP 9-10 study �NCHRP 9-10 Program 2007�. Fig. 7 showsthe accumulated compliance for binders 1 and 2 over the52 cycles. Other binders followed similar trends. From thegraphs, it is observed that the addition of Sasobit significantlylowers the deflections in the binder compared to the base binder.The addition of Aspha-Min, however, had different effects whenadded to the five binders. Since Aspha-Min is inorganic, the re-sponse to the repeated creep and recovery cycles may have to dowith the physical filling effect of the additive in the binders.

Temperature Sweep

A temperature-sweep test was conducted between 25 and 80°C todetermine the dependence of the complex modulus G* and thephase angle � of the five binders with and without the warmasphalt additives on temperature. The results of the temperature-sweep tests for binders 1 and 2 are shown in Fig. 8. Other bindersfollowed similar trends. From the graphs, it can be seen that thewarm asphalt additives do not have much effect on the complexmodulus G* of the binders over the entire range of temperatures.However, the addition of Sasobit to binders 2, 3, and 4 tends to

Time, s0 100 200 300 400 500 600

0.00

0.02

0.04

0.06

0.08

0.10


e, s0 200 250 300

Binder 1Binder 1 + ABinder 1 + S

(b)

c)

modified Binder 1 at—�a� 3; �b� 10: and �c� 50 Pa

Compliance,1/Pa

Tim0 15

(

asobit


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lower the phase angle � especially at lower temperatures, whichsuggests that the binders with Sasobit have improved elasticity atlower temperatures.

Conclusions

In this project, two different warm asphalt additives were studiedwith five different asphalt binders. The properties of the binderscontaining the warm asphalt additives are not studied in greatdetail, especially the rheological properties at midrange tempera-tures. Therefore, this limited study was carried out to determinesome of the effects of warm asphalt additives on the properties ofbinders. From the study, the following can be concluded.• From the GPC analysis, it was observed that Aspha-Min,

which is inorganic, had no significant effect on the binders.However, Sasobit lowered the LMS of Binder 1 significantly.Sasobit caused a reduction in the LMS, which suggests that themixtures with Binder 1 will be more prone to rutting. How-ever, from other tests, it was observed that Sasobit actuallyincreased the stiffness of the binders, which would make themix more resistant to rutting.

• All five virgin binders follow Newtonian flow at 60°C. Addi-tion of Aspha-Min does not affect the flow properties of thetested binders, whereas the addition of Sasobit causes shearthinning flow characteristics in the binders at 60°C.

• The addition of warm asphalt additives significantly increasesthe viscosities of the binders at 60°C. While the increase inthe viscosity due to Aspha-Min could be because of the filling

Time, s0 10 20 30 40 50470 480 490 500 510 5

Compliance,1/Pa

0.00

0.05

0.10

0.15

0.20

0.25

0.30


(a)

Fig. 7. Repeated creep-recovery curves affected

Temperature, oC

30 40 50 60 70 80

G*,Pa

102

103

104

105

106

107

0

10

20

30

40

50

60

70

80

90

Binder 1 (G*)Binder 1+A (G*)Binder 1+S (G*)Binder 1 (δ)Binder 1+A (δ)Binder 1+S (δ)

(a)

Fig. 8. Temperature dependence of complex m



effect of the additive, Sasobit is an aliphatic hydrocarbon,which recrystallizes in the binders at midrange temperatures,increasing the viscosity and stiffness.

• In the studied frequency ranges of 0.01–100 Hz, Sasobit in-creased the stiffness of the binders at any given frequency. Theaddition of Aspha-Min also increased the stiffness of the bind-ers, but not as much as Sasobit. Also, the increase in the stiff-ness by the addition of Aspha-Min could be only due to thefilling effect of the additive.

• Binders containing Sasobit showed lower compliance com-pared to the base binders, which means that they are stiffer andare more resistant to penetration at midrange temperatures.Also, after the stress was removed, the binders with Sasobitshowed lower permanent deformation when compared to thebase binders.

• Binders containing Aspha-Min also showed lower compliancevalues compared to the base binders in most cases, however,no trend was observed regarding the recovery of the binderswhen the stress was removed.

• When repeated creep-recovery tests were performed, binderscontaining Sasobit showed significantly lower permanent de-formation compared to the base binders. Binders containingAspha-Min also showed lower compliance values, but the re-duction in the permanent deformation was different with dif-ferent binders. Thus, it was concluded that since Aspha-Minacts only as mineral filler after the initial foaming, the stiffen-ing effect of the additive must be dependent on the binderproperties.

• From the temperature-sweep tests, it was observed that the

Time, s0 10 20 30 40 50470 480 490 500 510 520

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warm asphalt additives did not have any significant effect onthe complex modulus, G* of the binders between 25 and80°C. However, binders with Sasobit seemed to show lowerphase angle compared to the base binders, especially at lowertemperatures, which suggests improved elasticity of the bind-ers at lower temperatures.

References

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Documents

Midrange Temperature Rheological Properties of Warm Asphalt Binders