review article influence of antioxidant-enhanced polymers...

Review ArticleInfluence of Antioxidant-Enhanced Polymers inBitumen Rheology and Bituminous Concrete MixturesMechanical Performance

Samer Dessouky1 Mohammad Ilias2 Dae-Wook Park3 and In Tai Kim4

1Department of Civil and Environmental Engineering University of Texas at San Antonio One UTSA CircleSan Antonio TX 78249-0668 USA2Fugro Roadware Inc 8613 Cross Park Drive Austin TX 78754 USA3Department of Civil Engineering Kunsan National University 558 Daehak-ro Kunsan Chellabuk-do 573-701 Republic of Korea4Department of Transportation Engineering Myongji University San 38-2 Namdong Yongin-siGyeonggi-do 449-728 Republic of Korea

Correspondence should be addressed to In Tai Kim kit1998mjuackr

Received 21 August 2015 Accepted 3 November 2015

Academic Editor Jun Liu

Copyright copy 2015 Samer Dessouky et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

This paper evaluates the effect of polymer enhancement with antioxidant in the rheological properties of bitumen and mechanicalproperties of bituminous concrete mixture (BCM) In this study two antioxidant-enhanced polymers were utilized in mitigatingbitumen hardening due to agingThe rheological testing consists of temperature sweep using Dynamic Shear Rheometer at variousaging conditions Critical stiffness temperature data from the sweep test suggested that enhanced polymer exhibits less long-termhardening and brittleness compared to standard polymer The mechanical testing consists of dynamic modulus indirect tensileflow number and beam fatigue tests on BCM exposed to short-term aging Hamburg wheel tracking test was also performedto assess moisture-damage susceptibility It is found that the enhanced-polymer BCM exhibited higher modulus higher tensilestrength ratio improved rutting resistance lower moisture-damage susceptibility and slightly increased fatigue life as compared tostandard-polymer BCM

1 Introduction

Polymers are amongst the most common bitumen modifiersThey are used to improve bitumen thermoplastic character-istics flexibility under loading and thermal stability underenvironmental changes Their role in bitumen modificationdepends primarily on their physical properties contentsources and chemical compositions [1] The deterioration ofthe polymer-modified bitumen (PMB) over time is depen-dent on the combined effect of bitumen oxidation (aging) andpolymer degradation [2] This occurs during the in-servicephases of construction and traffic due to exposure to temper-atures shear forces and air The aging changes the molecularstructure and degrades the chemical composition of thepolymers and bitumen Aging in bitumen causes hardening

due to loss of volatile oil components and rearrangement ofbitumen molecules

Different types of polymers can alter the bitumenproperties differently Styrene-butadiene-styrene (SBS)styrene ethylene-butylene-styrene (SEBS) EVA (ethylenevinyl acetate) and EBA (ethyl butyl acetate) are commonpolymers used in bitumen modifications EVA and EBAimproved the binder performance at high temperature whileSBS and SEBS are effective over a wide range of temperatures[3] Airey [4] remarked that SBS polymer improves therheological properties at high temperature and increaseselastic properties at low frequency but has insignificant effectat low temperature Kok and Colak [5] noted that mixtureswith crumb rubber-modified bitumen outperformed the SBSmodification Sengoz and Isikyakar [3] analyzed standard SBS

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 214585 9 pageshttpdxdoiorg1011552015214585

2 Advances in Materials Science and Engineering

polymer at different percentages in bitumen physical prop-erties and mixtures mechanical properties They found thatpenetration was decreased softening point was increasedand temperature susceptibility was decreased with increasingpolymer content Based on the mechanical properties ofBMC they stated that stability and indirect tensile strengthwill increase when the polymer content does not exceed 5

The effectiveness of the polymer modification tendsto diminish as bitumen undergoes aging When polymersdegrade they experience a change in their physical andchemical properties resulting in loss of their thermoplas-tic characteristics This in turn results in decreased PMBresistance to cracking reduced durability and shortenedservice life Several studies investigated the aging effect onPMB Wu et al [6] studied the influence of aging on theevolution of structuremorphology and rheology of bitumenLu and Isacsson [7] studied the effect of aging on bitumenchemistry and rheology Durrieu et al [8] looked into theinfluence of ultraviolet radiation on bitumen aging Li et al[9] remarked that the aging process of polymers involved fourstages namely initiation growth transfer and terminationof free radicals During aging free radicals are formed frombreakage of polymer chain bonds caused by their exposureto heat or light These free radicals are ready to oxidize assoon as they come in contact with oxygen forming peroxyradicals (ie peroxides) These peroxy radicals further reactwith polymers to formnew free radicals and this cycle repeatsitself

One of the methods used to mitigate aging is the antioxi-dants (AO) additivesTheAO act in two different ways eitherby inhibiting the formation of peroxides or by scavenging thefree radical Li et al [9] observed that AO work as scavengersof free radicals facilitating the decomposition of hydroperox-ides which improve the aging resistance The AO also slowdown the age hardening of bitumen resulting in softer behav-ior at lower and higher temperatures Hydrated lime [10]Vitamin E and DLTDP [11] and zinc dialkyldithiophosphate[12] are examples of stand-alone antioxidants that are usedto mitigate aging for bitumen Hindered amine stabilizersand hindered phenolic and sulfur compounds are examplesof antioxidants that terminate the chain through reactionwith peroxyl radicals Plancher et al [10] study the effect ofhydrated lime on the hardening of BCM suggesting that theaging index of lime treatedmixtureswas lower than untreatedones The aging index was also dependent on the aggregatesand bitumen sources used in the experiment Apeagyei et al[13] evaluated the effects of AO on rheological properties ofPMB at different aging levels They reported that PMB withAOexhibited higher stiffness at higher temperature and lowerstiffness at lower temperature as compared to unmodifiedPMBThe study remarked that mixtures with AO control thereduction in creep compliance due to aging and enhancedthe tensile strength as compared to unmodified mixturesApeagyei [11] evaluated the age hardening of bitumenblendedwith numerous AO Depending on the rheological propertyhe noted that a combination of DLTDP (dilauryl thiodipropi-onate) and furfural represented the lowest aging index amongall AO-enhanced bitumenmaterialsThe study observed that

Table 1 Technical data of the two polymers

Polymer properties Conventional SBS SP CPToluene viscosity cP 2300 4000 1900Volatile matter max 040 075 050Total styrene 315 25 32

AO soften the bitumen at lower temperature and stiffen it athigher temperature

There are numerous studies that address the AO effect inaging retardation for base bitumen polymers and PMB [1ndash3 6 8 12 18] The current literature suggests limited studiesthat investigate the AO embedded in polymers to enhancePMBperformanceTherefore this study aims to fill in this gapand investigate the effectiveness of AO-enhanced polymersin mitigating age hardening for PMB and BCM The agehardening in the PMB will be quantified using the complexmodulus index by comparing the enhanced and controlbitumen The age hardening will be indirectly quantifiedin the BCM through comparing the performance-relatedmechanical properties attributed to aging (eg dynamicmodulus flow number moisture damage and fatigue) forenhanced and control mixes The uniqueness of these AO-enhanced polymers is that they are pretreated with hinderedphenols at 3 byweight of polymers during their productionWith the rising cost of crude oil there is a pressing need tomaximize the PMB durability and service life

2 Materials

Two AO-enhanced polymers were used in this study namelyS-polymer (SP) and C-polymer (CP) The SP is a SBSBlock polymer consisting of 25 styrene content and 175polystyrene block The SP is a widely used polymer forimproving bitumen stiffness and thermal stability The CP isa 6832 SEBS polymer that helps improve ductilityThe prop-erties of the polymers are shown in Table 1 A conventionaluntreated SBS polymer was used as a base

Unmodified neat bitumen (PG 64-22) was blended withall polymers A 3 polymer content by weight of bitumenwas used to enhance stiffness and ductility at high and lowtemperature respectively [14 15]The polymers were blendedusing a high-shear heavy-duty mixer at speed of 1500ndash2000 rpm for 4-5 hours at 149∘C The mixing temperaturewas identified by the polymer supplier After the mixingfull dispersion was achieved and no phase separation wasnoticed [14] The result of the bitumen-polymer blendingwas a performance grade (PG) 70-22 Three types of PMBare evaluated in this study conventional nonenhanced SBSmodified bitumen referred to here as PG70 and two AO-enhanced PMB referred to as CP and SP All PMB containthe same polymer content at 3 by weight of bitumenBituminous concrete mixtures (BCM) were molded usingthe three PMB to evaluate the effectiveness of AO-enhancedpolymers in the mechanical properties The mixture consistsof locally sourced fine-grained limestone and 5 PMBcontent by weight of aggregates meeting Texas Departmentof Transportation specifications for dense graded design All

Advances in Materials Science and Engineering 3

Table 2 Aggregate gradation and mixture volumetric properties

Sieve size (mm) 19 125 95 475 236 06 03 0075Passing percent() 100 100 992 638 382 168 117 33

Voids in mineralaggregate (VMA) 154

Bulk specificgravity at119873des

2366

Maximum specificgravity 119866mm

2456

Effective specificgravity 119866mb

2658

mixtures were short-term oxidized for four hours in an air-circulating oven at 165∘C as recommended by the bitumensupplierThe agedmixtures were compacted to achieve targetair voids of 7ndash9 using Superpave gyratory compactor withvolumetric properties as shown in Table 2

3 Laboratory Testing

Aging of bitumen causes distinctive characteristics for BCMsuch as reduction in fatigue life decreasing tensile strengthand ductility increasing moisture-damage susceptibility andincreasing rutting and shear resistance Therefore the exper-imental program was chosen to assess these characteristicsby testing the aging-related rheological properties of PMB aswell as the mechanical properties of BCM The rheologicaltesting of PMB included temperature sweep using DynamicShear Rheometer (DSR) at various aging conditions Themechanical performance testing included dynamic modulusindirect tensile flow number and four-point beam fatiguetests Testing was performed using the Universal TestingMachine a hydraulic-driven load frame system with thermalcontrol capability Moreover the Hamburg wheel trackingtesting was performed to evaluate the moisture susceptibilityusing the Asphalt Pavement Analyzer system

4 Rheological Analysis of PMB

Aging affects the rheological properties and temperature sus-ceptibility of bitumen Mastrofini and Scarsella [2] remarkedthat aging substantially changes the bitumen properties athigh temperature The reason is that the properties of bitu-men are affected by the existence of asphaltenes andmalteneswhich tend to degrade under aging In this study rheologicalproperties were assessed using the temperature sweep testingusing DSR on 25mm diameter and 1mm thick bitumenspecimen at temperature range of 20ndash100∘C and frequency of10 radsec at different aging conditions [16] The test assessesthe PMB viscoelastic behavior at a wide range of in-servicetemperatures at different aging states Each specimen wastested at two aging states rolling thin film oven (RTFO)aged and pressure aging vessel (PAV) aged conditions Thetest provides the viscoelastic properties (eg complex shearmodulus |119866lowast| and phase angle 120575) evolution with respect to

temperature in the form of isochronal plots The isochronalplots are used to evaluate the effect of temperature on |119866lowast|and 120575 due to aging [4] as shown in Figure 1 As expected theshear modulus decreases from an elastic-like behavior at theintermediate temperature (20∘C) to a viscous-like behavior athigh temperaturesThe flattened response at the intermediaterange (20ndash40∘C) of the PAV sample suggests that |119866lowast| is rela-tively constant over these temperaturesThis flattened range isexpanded as the bitumen undergoes aging It is expected thatthe polymer network after PAV has been completely aged inwhich the PMB stiffness becomes less sensitive to tempera-ture changes This can also be attributed to the formation ofa rigid network block created by the action of the polymers[17] at aged condition Moreover the extent of hardening isobserved as |119866lowast| increases due to PAV aging compared toRTFO only particularly at higher temperature range Theinfluence of the AO-enhanced polymers is apparent in twoaspects of the bitumen behavior The first consists of thehigher modulus observed for the SP and CP particularly athigh temperatures This suggests improving stiffness whichis a desirable characteristic for rutting resistance early inthe pavementrsquos life The second consists of slightly softerbehavior for the CP at the intermediate temperature rangeThis suggests improving ductility a desirable characteristicfor enhancing fatigue resistance of pavement

The phase angle represents the ratio of dissipated energyto stored energy ranging from 0∘ for elastic to 90∘ forviscous materials Measurements suggested that PMB exhib-ited increased elastic behavior as temperature decreasedand aging level increased The enhanced PMB SP and CPincreased the elastic behavior at high temperatures after agingas suggested by the decrease in phase angle The SP exhibitedhigher viscous-like behavior at intermediate temperaturesafter PAV suggesting improved bitumen long-term flexibilityand durability

Figure 2 is referred to as the black diagram defined asthe relationship between |119866lowast| and phase angle excludingthe effect of temperature [4] The figure suggests that as|119866lowast

| increases the phase angle decreases However a sharpdrop in the phase angle is remarked as the modulus exceeds200 kPa at which PMB behaves as an elastic-like materialUnder unaged condition the enhanced polymers reduce |119866lowast|and phase angle as compared to the standard polymers Thisbehavior continues as the PMB undergo RTFO and PAVaging However as |119866lowast| exceeds 200 kPa the black diagramdepicts crossover in which the modulus of the enhancedPMB exceeds the control one Moreover long-term aginghas tendency to eliminate the effect of enhanced polymer inthe rheological testing as shown in Figure 2(c) The blackdiagram presented insignificant difference between CP andSP The diagram suggests that the AO-enhanced polymersincrease the modulus of the PMB as compared to standardpolymer under low shear conditions and inversely reduce thestiffness under high-shear conditions

5 Aging of PMB

Aging of bitumen is a combination of two processesirreversible due to chemical reaction and reversible due


PG70SPCP

RTFO PAV

100

1000

10000

100000

1000000

|Glowast|

(Pa)

40 60 80 10020Temperature (∘C)

0

30

60

90

Phas

e ang

le (d

eg)

PG70SPCP

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)

Figure 1 Isochronal plots for RTFO and PAV aged PMB

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(a) Unaged

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90Ph

ase a

ngle

(deg

)

(b) RTFO

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(c) PAV

Figure 2 Black diagram for (a) unaged (b) RTFO and (c) PAV aged PMB


CP703

227

860

200

400

600

800

CMI (

)

RTFOPAV


PG70567

202

730

200

400

600

800CM

I (

)


SP538

234

860

200

400

600

800

CMI (

)


Figure 3 CMI showing the critical stiffness temperatures of bitumen

to physical changes resulting in hardening Ouyang et al[12] studied the aging resistance of PMB enhanced withAO additives (eg zinc dialkyldithiophosphate and dibutyldithiocarbamate) using Fourier Transform Infrared (FTIR)spectroscopy They remarked that AO worked as agingresistant agents by producing carbonyl in the modified bitu-men Cortizo et al [18] performed rheological and infraredspectroscopy testing on PMB in different aging states andnoted that the hardening of PMB depends on structuralcharacteristics of the added polymers In addition duringthermal degradation of PMB higher molecular size wasformed due to free radical reaction and due to the existenceof the polar compounds They found that the aging index ofPAV for PMB is more than that of RTFO Lu and Isacsson[1] remarked that the property of PMB depends not onlyon the properties of polymers but also on the source andproperties of base bitumen In their study they used differentpolymers (SBS SEBS EVA and EBA) and three types of basebitumen Based on the rheological properties of base bitumenand PMB they found that SBS and SEBS showed betterperformance than EVA and EBA EVA and EBA improvedPMB performance at high temperature while SBS and SEBSimproved performance over a wide range of temperaturesFor instance the PMB creep stiffness was reduced more inthe case of SBS and SEBS than that for EVA and EBA atminus35∘C Li et al [9] attempted to improve the thermal agingresistance of SBS polymer by using AO They found that AOimproved resistance to thermal hardening based on dynamicmechanical analysis and FTIR spectroscopy testing

In this study the hardening effect of the AO-enhancedPMB was evaluated by determining the critical stiffnesstemperature using unaged and aged measurements [14]Critical stiffness temperature is referred to as the tempera-ture corresponding to the peak stiffness of bitumen due toaging It also represents the highest resistance to permanentdeformation under oxidative conditions To determine thepeak stiffness the complex modulus indices (CMI) weredetermined based on |119866lowast| at oxidative conditions expressedas follows

CMI(RTFO) = 100 times [

[

10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(1)

CMI(PAV) = 100 times [

[

(10038161003816100381610038161003816119866lowast

(PAV)10038161003816100381610038161003816minus10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816)

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(2)

Equations (1) and (2) represent the bitumen hardeningdue to aging by RTFO and PAV independently For instancethe hardening effect of RTFO is subtracted in (2) to isolate theaging effect of PAVThe CMI provides a quantifiable measureof bitumen thermal stabilityThis index associates the changein aged with unaged properties as temperature changes [15]Bitumen with high thermal sensitivity is indicated by highCMI (ie greater than 100) and vice versa Representationof the CMI as a function of temperature is shown in Figure 3The figure depicts that the critical temperature coincides withthe RTFO and PAV aging The figure also depicts that the


PG70SPCP

10E minus 05 10E minus 02 10E + 01 10E + 04 10E + 0710E minus 08

Reduced frequency (Hz)

10

100

1000

10000

100000

Elowast

(MPa

)

Figure 4 119864lowast master curve at reference temperature of 21∘C

critical temperature increases significantlywhen an enhancedpolymer is used The critical temperature is 73 86 and 86∘Cfor PG70 SP and CP respectively After RTFO SP and CPmarginally increased CMI at all testing temperatures andparticularly by 158 and 123 at the critical temperaturerespectively It is suggested that the enhanced polymer tendsto exhibit more hardening at elevated temperature whichis preferable to improve rutting resistance in early life ofBCM Using the difference in CMI at the correspondingtemperatures for each PMB it was determined that CP andSP have increased short-term hardening at high temperaturerange (64ndash86∘C) by 11 and 17 respectively After PAV CPhas significantly reduced the long-term hardening (improvedfatigue cracking resistance) at intermediate temperaturerange (20ndash36∘C) SP has reduced the long-term hardeningat high temperature range (64ndash86∘C) by 15 At the criticaltemperatures in particular the CMI is 567 538 and 703for PG70 SP and CP respectively

6 Mechanical Testing Analysis of Mixture

Dynamic modulus testing was conducted according toAASHTOTP62-07 [19] at temperatures of 4 21 and 37∘Candfrequencies of 01 05 10 5 10 and 25Hz The significanceof this test is to determine |119864lowast| a viscoelastic materialproperty of BCM that reflects its stiffness at a wide rangeof temperatures andor frequencies in the form of a mastercurve Compacted BCM of 100mm in diameter and 150mminheight at air voids of 6ndash8were used to establish themastercurve at a reference temperature of 21∘C as shown in Figure 4Using the experimental data and the extrapolation techniqueby Christensen et al [20] one can extend the master curve toa larger frequency range Equation (3) was used to form themaster curve

log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)

where 119864lowast is the dynamic modulus 119905 is the loading time 119879 isthe temperature (∘K)Max is the limitingmaximummodulus

Table 3 Results of IDT testing

Properties PG70 SP CPDry tensile strength (kPa) 620 plusmn 40 590 plusmn 18 592 plusmn 80Wet tensile strength (kPa) 309 plusmn 19 354 plusmn 30 364 plusmn 21Tensile strength ratio () 500 600 615

and 120573 120575 120574 andΔ119864119886are fitting parameters from experimental

dataThe three mixes exhibit a similar glassy modulus plateau

of 21000MPa at high loading frequencies It is suggested thatthe effect of enhanced polymer in BCMmodulus is irrelevantat high frequency but has a distinct effect as frequencydecreases For instance at low frequency the enhancedSP mixture exhibited a 20 higher modulus compared toother mixtures In the intermediate frequency range (1ndash100Hz) a potential condition for permanent deformationthe enhanced SP and CP mixtures exhibit higher |119864lowast| com-pared to the control mixture For example at frequency of16Hz corresponding to 01 sec loading time [21] |119864lowast| forPG70 SP and CP are 274119864 + 03 375119864 + 03 and 383119864 + 03respectively

Indirect tensile (IDT) testing was performed to evaluatethe effect of enhanced polymer in the tensile strength ofBCMafter freezethaw conditioning Specimenswith 100mmdiameter and 635mm thickness following AASHTO T 283[22] were used Six replicates were molded for control andenhanced BCM with three tested after dry conditioning andthree after wet conditioning Freezethaw conditioning ofBCM specimens was performed at minus18∘C for 16 hours fol-lowed by water submerging at 60∘C for 24 hr and submergingat 25∘C for 2 hr The IDT testing was performed by applyinga monotonic vertical load along the diametral directionof the specimen until failure The IDT testing results aresummarized in terms of the average and standard deviationof dry and wet tensile strength data (Table 3) The coefficientof variation for each mixture is less than 15 which isan acceptable value considering the heterogeneity of themixtures coupled with the uncontrolled splitting initiationand evolution in the IDT It is also noticed that the tensilestrength ratio is greatly below the standard threshold of 80[22] The intention in this test is to compare the IDT resultsand not to compare the mixes against specification criteria

The IDT results suggest that the dry tensile strength ofthe control mixtures is higher by 5 than enhanced-polymermixtures On the contrary the enhanced-polymer mixturesexhibit higher wet tensile strength by an average of 16The tensile strength ratio of wet to dry specimens suggeststhat the freezethaw conditioning reduced the strength by50 for the standard-polymer mixtures and 40 for theenhanced-polymer mixtures These results suggest that theAO enhancement improved bitumen-aggregate bonding andreduced moisture-damage susceptibility This supports therationale that AO sustain polymer ductility and mitigatehardening and aging It is worth mentioning that none of themixtures satisfied the minimum tensile strength ratio valueof 80 as recommended by AASHTO T 283 [22]


SIP

4 6 8 10 120 2Number of passes (thousands)

16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)

Figure 5 The rutting evolution for SP mixture using HWTT

The Hamburg Wheel Tracking Tester (HWTT) was uti-lized to evaluate mixture susceptibility to moisture damagedue to the lack of insufficient bitumen coating structuralweakness of aggregates and weak bonding at bitumen-aggregate interface This test was performed on two com-pacted specimens with 150mm diameter and 62mm thick-ness for each polymer type [23] The testing was operatedby applying a steel wheel carrying 703N load rolling overthe mixtures at speed of 035ms rate of 50 passes perminute and temperature of 50∘C As the wheels roll overthe submerged specimens a combined effect of verticalstresses andmoisture infiltration tends to break the bitumen-aggregate bonding and induce rutting Testing was ter-minated at a maximum rut depth of 125mm or 20000passes whichever occurs first Figure 5 shows an exampleof the rut depth evolution with number of passes for theSP mixture The rutting rate defined as the slope of therut depth versus number of passes increases rapidly as thespecimen approaches the failure criteria The increase in therate is because the mixtures undergo accumulated phasesof stripping and moisture damage The point (number ofpasses) where the rutting rate changes is referred to as astripping inflection point (SIP) Low SIP is associated withmixtures with high moisture-damage susceptibility and viceversa More information on SIP can be found elsewhere [24]

The HWTT results in Table 4 remarked that BCM withenhanced polymer are less moisture-damage susceptiblecompared to the one with control polymer SP and CPexhibited less rutting depth higher number of loading passesto failure higher SIP and overall less rutting rate SP in par-ticular expressed the best performance among all mixturessupporting the effectiveness of the AO role in mitigatingpolymer and bitumen aging

To evaluate the rutting resistance of the BCM the flownumber (FN) test was employedThe FN is determined as thenumber of load cycles corresponding to the minimum rateof axial strain deformation for mixture under uniaxial stressconditions [25] Mixtures with higher FN are associated withhigher rutting resistance and vice versa Cylindrical speci-mens similar to the dynamic modulus test were subjected to

Table 4 Hamburg wheel tracking testing results

Parameters PG70 SP CPMax rutdepth 136 plusmn 02 129 plusmn 08 132 plusmn 09

Number ofpasses 6719 plusmn 3208 10200 plusmn 31 9271 plusmn 1415

Rutting rate(mmpasses) 0002 plusmn 01 00012 plusmn 0001 00014 plusmn 001

SIP 3525 plusmn 1237 6225 plusmn 106 4800 plusmn 1980

PG70SPCP

Secondary (PG70)

Tertiary (SP)Secondary (SP)

Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)

Figure 6 Uniaxial strain measurements of FN test

repeated haversine axial cycles with 01 sec loading and 09 secrest period [26] The test was performed under unconfinedconditions for two replicates at 54∘C and deviatoric stressof 207 kPa Failure criteria were identified by axial strain of50000microstrains or number of cycles of 15000 whicheveroccurs first

During the FN test the mixture undergoes three stagesof creep strain deformation namely primary steady state(secondary) and tertiary deformation [25] The strain evo-lution of the BCM is represented in Figure 6 Results showedthat control BCM reached tertiary flow earlier compared tothe enhanced BCMThe tertiary flow approximately initiatedat 5000 10000 and gt15000 cycles for PG70 SP and CPrespectively On the other hand accumulated strain in CPmixture was the lowest among all mixtures without initiationof tertiary creep deformation

Table 5 suggests that enhanced-polymer BCM have sig-nificantly higher FN as compared to the control The FNincreases 3 and 4 times when SP and CP enhanced polymerswere utilized respectively Results suggest that AO enhance-ment sustains polymer physical characteristics resulting inimproving BCM rutting resistance as compared to standardpolymersThese results are in agreement with |119864lowast| propertiesin Figure 4 in which the control BCM induced the leastmodulus among all mixtures

To assess the BCM fatigue characteristics the four-pointbeam fatigue tester was utilized Repeated bending load was


Table 5 Flow number test data

Parameters PG70 SP CPFlownumber (FN) 1585 plusmn 527 4597 plusmn 763 6437 plusmn 122

Rate of strainat FN 20 plusmn 06 038 plusmn 018 038 plusmn 018

Microstrainat FN 13000 plusmn 1058 11700 plusmn 200 10461 plusmn 2480

Terminatingnumber ofcycles

5792 plusmn 2600 15000 15000

Maximumstrain(micron)

50000 43540 plusmn 9149 17617 plusmn 6490

Table 6 Beam fatigue test data

Parameters PG70 SP CPAverage119873

119891

(1000 cycles) 884 1000 898Std deviation (lowast1000) 102 0 177COV () 115 0 20

applied on BCM beams to determine flexural stiffness Thebeam stiffness is determined by the ratio of the maximumtensile stress and the maximum tensile strain As the beamundergoes repeated flexural loading the mixture stiffnessdrops Terminating flexural stiffness is half the initial beamstiffness The number of cycles corresponding to the termi-nating stiffness is referred to as the fatigue life (119873

119891) The

strain-controlled test was performed using four point loadingpins 119mm apart over 380mm length 50mm thicknessand 63mm width BCM beams As suggested by AASHTOT 321 [27] the strain level should be between 250 and750 microstrains therefore testing was conducted at 300microstrains frequency of 10Hz and temperature of 21∘CSix replicate beams were tested to establish the strain-fatiguelife relationship Mixtures were manually compacted in slabsusing an in-house steel mold to achieve 7ndash9 air voids

Table 6 presented the average and standard deviation offatigue life for each mixture As shown in the table thebeam fatigue testing suggests that the mixes exhibit slightimprovement in the fatigue life with the AO additives Thetable suggested that the fatigue life improved by 13 and2 with SP and CP enhanced mixtures respectively Thevariability in the testing results was less than 20 which isacceptable for these kinds of tests that are normally knownfor their high variability

7 Conclusion

An experimental program was established to investigatethe influence of AO-enhanced polymers on mitigating agehardening of bitumen and improving BCMmechanical prop-erties The AO-enhanced polymer effect was evident in therheological testing of the PMB The enhancement increasedshear stiffness and improved the elasticity of short-term agedPMB at high in-service temperatures The CP enhancement

has shown improvement in the ductility of the long-termagedPMB at intermediate temperatures

Theperformance of theAO-enhancedpolymer appears toimprove BCM stiffness and increase fatigue life The stiffnessincrease of bitumen due to enhanced-polymer modificationwas reflected in increasing dynamic modulus and ruttingresistance The study also suggested that the AO-enhancedpolymers improved bitumen-aggregate bonding and reducedmoisture-damage susceptibility and stripping as evident inthe HWTT and IDT results The AO-enhanced polymershave also improved BCM ductility and slightly increasedfatigue life in the beam flexural testing

Further study with different bitumen and aggregatesources is highly recommended Expanding the testing pro-gram to includemore performance-basedmechanical testingis essential to better understand the mechanism of AOenhancement in mixture behavior

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to thank Valero Energy Corporationfor providing the bitumen and Dynasol for providing thepolymers

References

[1] X Lu and U Isacsson ldquoEffect of ageing on bitumen chemistryand rheologyrdquo Construction and Building Materials vol 16 no1 pp 15ndash22 2002

[2] D Mastrofini and M Scarsella ldquoThe application of rheology tothe evaluation of bitumen ageingrdquo Fuel vol 79 no 9 pp 1005ndash1015 2000

[3] B Sengoz and G Isikyakar ldquoAnalysis of styrene-butadiene-styrene polymer modified bitumen using fluorescent micros-copy and conventional test methodsrdquo Journal of HazardousMaterials vol 150 no 2 pp 424ndash432 2008

[4] G D Airey ldquoRheological properties of styrene butadiene sty-rene polymer modified road bitumensrdquo Fuel vol 82 no 14 pp1709ndash1719 2003

[5] B V Kok and H Colak ldquoLaboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphaltrdquo Con-struction and Building Materials vol 25 no 8 pp 3204ndash32122011

[6] S-P Wu L Pang L-T Mo Y-C Chen and G-J ZhuldquoInfluence of aging on the evolution of structure morphologyand rheology of base and SBS modified bitumenrdquo Constructionand Building Materials vol 23 no 2 pp 1005ndash1010 2009

[7] X Lu and U Isacsson ldquoModification of road bitumens withthermoplastic polymersrdquo Polymer Testing vol 20 no 1 pp 77ndash86 2000

[8] F Durrieu F Farcas and V Mouillet ldquoThe influence of UVaging of a StyreneButadieneStyrene modified bitumen com-parison between laboratory and on site agingrdquo Fuel vol 86 no10-11 pp 1446ndash1451 2007


[9] Y Li L Li Y Zhang S Zhao L Xie and S Yao ldquoThe influenceof UV aging of a StyreneButadieneStyrene modified bitumencomparison between laboratory and on site agingrdquo Journal ofApplied Polymer Science vol 116 no 2 pp 754ndash761 2010

[10] H Plancher E L Green and J C Petersen ldquoReduction ofoxidative hardening of asphalts by treatment with hydratedlimemdasha mechanistic studyrdquo Proceedings of the Association ofAsphalt Paving Technologists vol 45 pp 1ndash24 1976

[11] A K Apeagyei ldquoLaboratory evaluation of antioxidants forasphalt bindersrdquo Construction and Building Materials vol 25no 1 pp 47ndash53 2011

[12] C Ouyang S Wang Y Zhang and Y Zhang ldquoImproving theaging resistance of styrene-butadiene-styrene tri-block copoly-mer modified asphalt by addition of antioxidantsrdquo PolymerDegradation and Stability vol 91 no 4 pp 795ndash804 2006

[13] A K Apeagyei W Buttlar and B J Dempsey ldquoInvestigationof cracking behavior of antioxidant-modified asphalt mixturesrdquoJournal of the Association of Asphalt Paving Technologists vol 77pp 517ndash548 2008

[14] S Dessouky C Reyes M Ilias D Contreras and A T Papa-giannakis ldquoEffect of pre-heating duration and temperatureconditioning on the rheological properties of bitumenrdquo Con-struction and Building Materials vol 25 no 6 pp 2785ndash27922011

[15] S Dessouky D Contreras J Sanchez A T Papagiannakisand A Abbas ldquoInfluence of hindered phenol additives on therheology of aged polymer-modified bitumenrdquoConstruction andBuilding Materials vol 38 pp 214ndash223 2013

[16] AASHTO T 315 ldquoDetermining the Rheological Properties ofAsphalt Binder Using a Dynamic Shear Rheometer (DSR)rdquoWashington DC USA


[18] M S Cortizo D O Larsen H Bianchetto and J L Alessan-drini ldquoEffect of the thermal degradation of SBS copolymersduring the ageing of modified asphaltsrdquo Polymer Degradationand Stability vol 86 no 2 pp 275ndash282 2004

[19] AASHTO ldquoDetermining dynamic modulus of hot mix asphalt(HMA)rdquo AASHTO TP 62-07 AASHTO Washington DCUSA 2007

[20] D W Christensen T Pellinen and R F Bonaquist ldquoHirschmodel for estimating the modulus of asphalt concreterdquo Journalof the Association of Asphalt Paving Technologists vol 72 pp97ndash121 2003

[21] I L Al-Qadi M Elseifi P Yoo et al ldquoAccuracy of currentcomplex modulus selection procedure from vehicular loadpulse inNCHRP 1-37Amechanistic-empirical pavement designguiderdquo Transportation Research Board vol 2087 pp 81ndash902008

[22] AASHTO T 283 Resistance of Compacted Hot Mix Asphalt(HMA) to Moisture-Induced Damage American Associationof State Highway and Transportation Officials (AASHTO)Washington DC USA 2010

[23] AASHTO T 324 Hamburg Wheel-Track Testing of compactedHot Mix Asphalt (HMA) American Association of State High-way and TransportationOfficials (AASHTO)Washington DCUSA 2013

[24] T Aschenbrener and G Currier ldquoInfluence of testing variableson the results from the Hamburg wheel tracking devicerdquo Tech

Rep CDOT-DTD-R-93-22 Colorado Department of Trans-portation Denver Colo USA 1993

[25] R N Dongre J A DrsquoAngelo and A Copeland ldquoRefinementof flow number as determined by asphalt mixture performancetester use in routine control-quality assurance practicerdquo Bitu-minous Materials and Mixtures vol 2 pp 127ndash136 2009

[26] AASHTO ldquoStandard method of test for determining thedynamic modulus and flow number for Hot Mix Asphalt(HMA) using the Asphalt Mixture Performance Tester(AMPT)rdquo AASHTO TP 79-09 AASHTO Washington DCUSA 2009

[27] AASHTO ldquoDetermining the fatigue life of compacted hot mixasphalt subjected to repeated flexural bendingrdquo AASHTO T321 AmericanAssociation of StateHighway andTransportationOfficials Washington DC USA 2011

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


polymer at different percentages in bitumen physical prop-erties and mixtures mechanical properties They found thatpenetration was decreased softening point was increasedand temperature susceptibility was decreased with increasingpolymer content Based on the mechanical properties ofBMC they stated that stability and indirect tensile strengthwill increase when the polymer content does not exceed 5

The effectiveness of the polymer modification tendsto diminish as bitumen undergoes aging When polymersdegrade they experience a change in their physical andchemical properties resulting in loss of their thermoplas-tic characteristics This in turn results in decreased PMBresistance to cracking reduced durability and shortenedservice life Several studies investigated the aging effect onPMB Wu et al [6] studied the influence of aging on theevolution of structuremorphology and rheology of bitumenLu and Isacsson [7] studied the effect of aging on bitumenchemistry and rheology Durrieu et al [8] looked into theinfluence of ultraviolet radiation on bitumen aging Li et al[9] remarked that the aging process of polymers involved fourstages namely initiation growth transfer and terminationof free radicals During aging free radicals are formed frombreakage of polymer chain bonds caused by their exposureto heat or light These free radicals are ready to oxidize assoon as they come in contact with oxygen forming peroxyradicals (ie peroxides) These peroxy radicals further reactwith polymers to formnew free radicals and this cycle repeatsitself

One of the methods used to mitigate aging is the antioxi-dants (AO) additivesTheAO act in two different ways eitherby inhibiting the formation of peroxides or by scavenging thefree radical Li et al [9] observed that AO work as scavengersof free radicals facilitating the decomposition of hydroperox-ides which improve the aging resistance The AO also slowdown the age hardening of bitumen resulting in softer behav-ior at lower and higher temperatures Hydrated lime [10]Vitamin E and DLTDP [11] and zinc dialkyldithiophosphate[12] are examples of stand-alone antioxidants that are usedto mitigate aging for bitumen Hindered amine stabilizersand hindered phenolic and sulfur compounds are examplesof antioxidants that terminate the chain through reactionwith peroxyl radicals Plancher et al [10] study the effect ofhydrated lime on the hardening of BCM suggesting that theaging index of lime treatedmixtureswas lower than untreatedones The aging index was also dependent on the aggregatesand bitumen sources used in the experiment Apeagyei et al[13] evaluated the effects of AO on rheological properties ofPMB at different aging levels They reported that PMB withAOexhibited higher stiffness at higher temperature and lowerstiffness at lower temperature as compared to unmodifiedPMBThe study remarked that mixtures with AO control thereduction in creep compliance due to aging and enhancedthe tensile strength as compared to unmodified mixturesApeagyei [11] evaluated the age hardening of bitumenblendedwith numerous AO Depending on the rheological propertyhe noted that a combination of DLTDP (dilauryl thiodipropi-onate) and furfural represented the lowest aging index amongall AO-enhanced bitumenmaterialsThe study observed that

Table 1 Technical data of the two polymers

Polymer properties Conventional SBS SP CPToluene viscosity cP 2300 4000 1900Volatile matter max 040 075 050Total styrene 315 25 32

AO soften the bitumen at lower temperature and stiffen it athigher temperature

There are numerous studies that address the AO effect inaging retardation for base bitumen polymers and PMB [1ndash3 6 8 12 18] The current literature suggests limited studiesthat investigate the AO embedded in polymers to enhancePMBperformanceTherefore this study aims to fill in this gapand investigate the effectiveness of AO-enhanced polymersin mitigating age hardening for PMB and BCM The agehardening in the PMB will be quantified using the complexmodulus index by comparing the enhanced and controlbitumen The age hardening will be indirectly quantifiedin the BCM through comparing the performance-relatedmechanical properties attributed to aging (eg dynamicmodulus flow number moisture damage and fatigue) forenhanced and control mixes The uniqueness of these AO-enhanced polymers is that they are pretreated with hinderedphenols at 3 byweight of polymers during their productionWith the rising cost of crude oil there is a pressing need tomaximize the PMB durability and service life

2 Materials

Two AO-enhanced polymers were used in this study namelyS-polymer (SP) and C-polymer (CP) The SP is a SBSBlock polymer consisting of 25 styrene content and 175polystyrene block The SP is a widely used polymer forimproving bitumen stiffness and thermal stability The CP isa 6832 SEBS polymer that helps improve ductilityThe prop-erties of the polymers are shown in Table 1 A conventionaluntreated SBS polymer was used as a base

Unmodified neat bitumen (PG 64-22) was blended withall polymers A 3 polymer content by weight of bitumenwas used to enhance stiffness and ductility at high and lowtemperature respectively [14 15]The polymers were blendedusing a high-shear heavy-duty mixer at speed of 1500ndash2000 rpm for 4-5 hours at 149∘C The mixing temperaturewas identified by the polymer supplier After the mixingfull dispersion was achieved and no phase separation wasnoticed [14] The result of the bitumen-polymer blendingwas a performance grade (PG) 70-22 Three types of PMBare evaluated in this study conventional nonenhanced SBSmodified bitumen referred to here as PG70 and two AO-enhanced PMB referred to as CP and SP All PMB containthe same polymer content at 3 by weight of bitumenBituminous concrete mixtures (BCM) were molded usingthe three PMB to evaluate the effectiveness of AO-enhancedpolymers in the mechanical properties The mixture consistsof locally sourced fine-grained limestone and 5 PMBcontent by weight of aggregates meeting Texas Departmentof Transportation specifications for dense graded design All






2366


2456


2658










5 Aging of PMB



PG70SPCP

RTFO PAV

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)

PG70SPCP

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)


PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(a) Unaged

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90Ph

ase a

ngle

(deg

)

(b) RTFO

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(c) PAV



CP703

227

860

200

400

600

800

CMI (

)

RTFOPAV


PG70567

202

730

200

400

600

800CM

I (

)


SP538

234

860

200

400

600

800

CMI (

)






[

10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(1)


[

(10038161003816100381610038161003816119866lowast

(PAV)10038161003816100381610038161003816minus10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816)

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(2)



PG70SPCP



10

100

1000

10000

100000

Elowast

(MPa

)





log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)










SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








2366


2456


2658










5 Aging of PMB



PG70SPCP

RTFO PAV

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)

PG70SPCP

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)


PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(a) Unaged

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90Ph

ase a

ngle

(deg

)

(b) RTFO

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(c) PAV



CP703

227

860

200

400

600

800

CMI (

)

RTFOPAV


PG70567

202

730

200

400

600

800CM

I (

)


SP538

234

860

200

400

600

800

CMI (

)






[

10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(1)


[

(10038161003816100381610038161003816119866lowast

(PAV)10038161003816100381610038161003816minus10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816)

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(2)



PG70SPCP



10

100

1000

10000

100000

Elowast

(MPa

)





log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)










SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




PG70SPCP

RTFO PAV

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)

PG70SPCP

100

1000

10000

100000

1000000

|Glowast|

(Pa)


0

30

60

90

Phas

e ang

le (d

eg)


PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(a) Unaged

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90Ph

ase a

ngle

(deg

)

(b) RTFO

PG70SPCP

1000 10000 100000 1000000100|Glowast| (Pa)

0

30

60

90

Phas

e ang

le (d

eg)

(c) PAV



CP703

227

860

200

400

600

800

CMI (

)

RTFOPAV


PG70567

202

730

200

400

600

800CM

I (

)


SP538

234

860

200

400

600

800

CMI (

)






[

10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(1)


[

(10038161003816100381610038161003816119866lowast

(PAV)10038161003816100381610038161003816minus10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816)

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(2)



PG70SPCP



10

100

1000

10000

100000

Elowast

(MPa

)





log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)










SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




CP703

227

860

200

400

600

800

CMI (

)

RTFOPAV


PG70567

202

730

200

400

600

800CM

I (

)


SP538

234

860

200

400

600

800

CMI (

)






[

10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(1)


[

(10038161003816100381610038161003816119866lowast

(PAV)10038161003816100381610038161003816minus10038161003816100381610038161003816119866lowast

(RTFO)10038161003816100381610038161003816)

100381610038161003816100381610038161003816119866lowast

(Unaged)100381610038161003816100381610038161003816

]

]

(2)



PG70SPCP



10

100

1000

10000

100000

Elowast

(MPa

)





log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)










SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




PG70SPCP



10

100

1000

10000

100000

Elowast

(MPa

)





log (119864lowast)

= 120575 +(Max minus 120575)

1 + 119890120573+120574log(119905)minus(Δ1198641198861914714)[(1119879)minus(129525)]

(3)










SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




SIP


16

14

12

10

8

6

4

2

0

Rut d

epth

(mm

)










PG70SPCP

Secondary (PG70)


Secondary (CP)

Prim

ary

Tertiary (PG70)

2500 5000 7500 10000 12500 150000Number of cycles

times104

0

1

2

3

4

5

Stra

in (120583

)












5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









5792 plusmn 2600 15000 15000


50000 43540 plusmn 9149 17617 plusmn 6490



119891



119891) The



7 Conclusion







Acknowledgments


References





































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



review article influence of antioxidant-enhanced polymers...

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