Research Article Investigations of Physical and Rheological...

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2013 Article ID 239036 7 pageshttpdxdoiorg1011552013239036

Research ArticleInvestigations of Physical and Rheological Properties ofAged Rubberised Bitumen

Asim Hassan Ali Nuha S Mashaan and Mohamed Rehan Karim

Center for Transportation Research Faculty of Engineering University of Malaya 50603 Kuala Lumpur Malaysia

Correspondence should be addressed to Asim Hassan Ali asimsiswaumedumy

Received 27 August 2012 Accepted 15 January 2013

Academic Editor Dachamir Hotza

Copyright copy 2013 Asim Hassan Ali 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

Several road pavement distresses are related to rheological bitumen properties Rutting and fatigue cracking are themajor distressesthat lead to permanent failures in pavement construction Influence of crumb rubber modifier (CRM) on rheological propertiesof bitumen binder such as improvement of high and intermediate temperatures is investigated in the binderrsquos fatigue and ruttingresistance through physical-rheological changes in this researchThe bitumen binders were aged by rolling thin film oven (RTFOT)to simulate short-term aging and pressure aging vessel (PAV) to simulate long-term agingThe effects of aging on the rheological andphysical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR) Brookfield viscometer testsoftening point test and penetration test The results showed that the use of rubberised bitumen binder reduces the aging effect onphysical and rheological properties of the bitumen binder as illustrated through lower aging index of viscosity lower aging index of119866lowastsin 120575 and an increase in Tan 120575with crumb rubbermodifier content increasing indicating that the crumb rubbermight improve

the aging resistance of rubberised bitumen binder In addition the results showed that the softening point increment (Δ119878) and pene-tration aging ratio (PAR) of the rubberised bitumen binder decreased significantly due to crumb rubbermodification Furthermorethe higher crumb rubber content the lower 119866lowastsin 120575 after PAV aging which led to higher resistance to fatigue cracking bitumen

1 Introduction

Several road pavement distresses are related to bitumen prop-erties Rutting and fatigue cracking are the major distressesthat lead to permanent failures in pavement constructionBitumen is a viscoelastic material its rheological propertiesare very sensitive to temperature and rate of loading Ingeneral road pavement performance properties are mainlyaffected by the bitumen binder properties it is well knownthat the rheological properties and durability of conventionalbitumen are not sufficient to resist pavement distresses Aconventional bitumen 80100 penetration grade is commonlyused in Malaysia and moreover it is subjected to the hightraffic load and hot climate The use of crumb rubber (wastetyre) in bitumen modification is considered as a sustainabletechnology which transforms unwanted residue into a newbituminous mixture Aging is known as a factor influencingthe performance and characteristics of bitumen binderMany

factors might contribute to this hardening of the bitu-men such as oxidation volatilisation polymerization andthixotropy [1] Field studies have shown that crumb rubbercan improve the bitumen pavement performance [2ndash5]

Mohamed et al [6] illustrated the influence of lowCRM content on rheological properties of aged bitumenreporting that the rheological changes in bitumen binderled to improving the mechanical properties of rubberisedbitumen binder In a joint experiment Abdelaziz and Karim[7] conducted a study on rheological evaluation of agedrubberised bitumen The results showed that CRM has anobvious significant effect on bitumen rheology by increasingcomplex shear modulus 119866lowast and decreasing phase angle 120575Also the RTFOT aging results of this study indicated that119866lowastwas increased by 1 to 15 times for unmodified bitumen and25 times for rubberised bitumen The PAV test indicated anincrease in complex shear modulus which was about 2 and 3times for unmodified and rubberised bitumen respectively

2 Advances in Materials Science and Engineering

The applications of rubberised bitumen binders havereported many advantages for instance improved bitumenresistance to rutting due to high viscosity high softeningpoint and better resilience reduction in road pavementmaintenance cost lower fatiguereflection cracking and lesstemperature susceptibility [8] In general the applicationof crumb rubber modified in bitumen binder can improvebinder properties by lowering the inherent temperature sus-ceptibility of binders [9 10] The use of crumb rubber mod-ifier with bitumen binder led to enhancing the fatigue resis-tance [11 12] The improved performance of bitumen rubberpavements compared with conventional bitumen pavementsis primarily a result of improved rheological properties of therubberised bitumen binder

A study by Aflaki and Memarzadeh [13] investigated theeffect of rheological properties of crumb rubber on fatiguecracking at low and intermediate temperatures using differentshear methodsThe results of this study showed that the highshear blending indicated more influence on improvement oflow-temperature properties of rubberised binder than thelow shear blending The mechanism by which binder prop-erties may change at low temperature was presented Thismechanism is referred to as physical hardening occurringat temperatures next to or lower than the glass transitiontemperature and causes significant hardening of the bitu-men binder Aging influenced the bitumen chemistry andrheology significantly additionally the use of the two agingconditions that is thin film oven test (TFOT) and rollingthin file oven test (RTFOT) showed a strong correlation andsimilar severity [14] The ideal use of bitumen binders aspavingmaterials is dependent on its resistance to the physicalchange across the range of temperatures encountered in aconventional pavement Aging significantly changed both thechemical and physical properties of asphalts Physical prop-erties such as penetration ductility viscosity and stiffness areall affected to some extent by aging [15]

Aging indexmeasurement is one of themost popular pro-cedures used to determine aging susceptibility and providesranking of different bitumen binders Aging index is definedas the ratio of a given binder property after aging to thatproperty before aging as shown in (1)

Aging index =Bitumen property after agingsame property before aging

(1)

11 Research Objective and Scope The primary objective ofthis research is to evaluate and investigate the influence ofcrumb rubber content on the rubberised binderrsquos rheologicaland physical changes subsequent to aging The secondaryobjective is to identify the degree of aging in rheological andphysical properties of rubberised bitumen and its effect onhigh-temperature properties (rutting) as well as intermediatetemperature (fatigue cracking) through short-term aging test(rolling thin film oven test (RTFOT)) and long-term agingtest (pressure aging vessel (PAV))

Table 1 Physical and rheological properties of 80100 PG bitumen

Test properties ResultsViscosity at 135∘C (Pa sdot s) 065119866lowastsin 120575 at 64∘C (kPa) 135

Ductility at 25∘C (cm) gt100Softening point (∘C ) 47Penetration at 25∘C (d-mm) 88Ductility after RTFOT at 25∘C (cm) gt100RTFOT aged 119866lowastsin 120575 at 64∘C (kPa) 6022PAV aged 119866lowastsin 120575 at 25∘C (kPa) 31225

Table 2 The chemical components of the original bitumen beforeand after ageing

Unaged After RTFOT After PAVSaturates () 151 1388 1247Aromatics () 4855 4419 3855Resins () 2622 2894 3121Asphaltenes () 1013 1299 1777

Table 3 (CRM gradation)

Sieve 119899 (size mm) Particle size distributionNo 10 (200) 100No 16 (1180) 100No 20 (0850) 100No 30 (0600) 977No 40 (0425) 611No 50 (0300) 339No 80 (0180) 125No 100 (0150) 75No 200 (0075) 00

2 Experimental Program and Materials

The base 80100 penetration grade bitumen was used in thisstudy Tables 1 and 2 show the properties of base bitumenand the chemical components of original bitumen (beforeand after aging) respectively Rubberised bitumen binder wasprepared by mixing bitumen 80100 penetration grade withCRM (8 and 16 by binder weight) passing the 30 meshsieve as shown in Table 3 the propeller mixer used to mixthe base bitumen and the crumb rubber at constant blendingconditions of 180∘C temperature time of 60 minutes andvelocity of 200 rpm

The samples were aged using the standard rolling thinfile oven test (RTFOT) (ASTM D-2872) at a temperatureof 163∘C for 85min as short-term aging and pressure agingvessel (PAV) (AASHTO PP1) at 100∘C and an air pressureof 21Mpa for 20 hours to simulate the long-term aging Toinvestigate the influence of oxidative aging on rheologicalchanges of rubberised bitumen the age hardening is evalu-ated bymeasuring Brookfield viscosity (135∘C)ASTMD4402penetration test (25∘C) ASTMD5 softening point test (25∘C)ASTM D36 and dynamic shear (DSR) ASTM D-4 Proposal

Advances in Materials Science and Engineering 3

Table 4 DSR condition test used in the current study

Rheologicalparameter

Plate Dia(mm)

Gap(mm) Sample 119879 (∘C)

119866lowastsin 120575 25 1 RTFOT 76119866lowastsin 120575 8 2 PAV 31

0500

100015002000250030003500400045005000

Visc

osity

at 1

35∘C

(MPa

middots)

0 4 8 12 16 20Crumb rubber content ()

UnagedRTFOTPAV

1198772

= 0999

1198772

= 0999

1198772

= 0992

Figure 1 Brookfield viscosity results versus crumb rubber content

P246 In this study the condition test of DSR test of parallelplate (diameter and gaps) frequency sweep and the testingtemperature for samples during RTFOT and PAV aging arelisted in Table 4

3 Results and Discussion

31 Performance Properties at High Temperature

311 Brookfield Viscosity at 135∘C The viscosity of bitumenbinders at high temperatures is an important property asit is a good indicator of the binderrsquos ability of pumpingthrough bitumen plant [16] Figures 1 and 2 show the viscosityresults of the rubberised bitumen tested in this study forvarious rubber contents and aging phasesconditions Asexpected the increase in crumb rubber content led to highviscosity of the rubberised binder Additionally the increasein viscosity of aged rubberised bitumen was about 36and 44 for rubber contents of 8 and 16 respectivelyunder RTFOT aging conditions while the increase in theviscosity under PAV aging values was about 78 and 82for rubber content of 8 and 16 respectively Thus theincrease in crumb rubber content has an obvious effecton aged rubberised bitumen viscosity compared to agedunmodified bitumen with correlation coefficient 1198772 = 0997The reason is the conversion to asphaltenes (the highestmolecular component fraction) of the other lower molecularweight asphalt components through oxidationThis is clearlyevidenced bymolecular weight analysis of asphalts before andafter aging as shown in Table 2

Figure 3 shows VAI of the original bitumen and therubberised binder after RTFOT and PAV aging VAI is the

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Visc

osity

at 1

35∘C

(MPa

middots)

Unaged RTFOT PAVAging phases

CR 0CR 8CR 16

Figure 2 Brookfield viscosity results of CRM binders versus agingconditions

0

05

1

15

2

25

3Vi

scos

ity ag

ing

inde

x

After RTFOT After PAV

CR 0CR 8CR 16

Figure 3 VAI of original and rubberised modified bitumen afterRTFOT and PAV

ratio of aged viscosity of the binder to the unaged viscosity ofsame binder as illustrated in (2) [17]

VAI =119881aged

119881unaged (2)

where VAI is the viscosity aging index119881unaged and 119881aged arethe viscosities of unaged and aged values of the binderrespectivelyThis exhibits that viscosity aging index of rubbermodified binder is significantly lower than that of unmodifiedbitumen thus indicating that the rubberised bitumen wouldimprove the thermooxidative aging properties of bitumenThis result can be explained by the chemical componentschange of the binder during the aging that led to the increase


0

10

20

30

40

50

60

70

80

90

PAR

()

0 8 10CRM content ()

RTFOTPAV

Figure 4 Effect of aging on penetration of bitumen binder

of the asphaltene content which was responsible for increas-ing the viscosity flow of the bitumen binder The viscosityaging index reflected better resistance of crumb rubber mod-ified bitumen to aging as it showed lower value after short-term aging RTFOT and long-term aging PAV respectivelyThus the use of viscosity aging index determines the effect ofaging of the original bitumen and modified bitumen whichprovides a much clearer effect of the hardening (aging) rate[17]

312 Penetration Aging Ratio Results The penetration agingratio is an alternative option to show the effects of aging on thephysical properties of the bitumen binder Penetration agingratio (PAR) can be defined as the ratio of aged penetrationvalue to unaged penetration as illustrated in (3)

PAR = (penetrationagedpenetrationunaged

) times 100 (3)

Figure 4 shows the penetration aging ratio of original andrubberised bitumen after rolling thin film oven test andpressure aging vessel test The results showed that the pen-etration of unmodified bitumen and rubberised bitumenbinders decreased after the two different aging In additionthe higher crumb rubber content the lower penetration agingratio which led to reducing the degree of aging of rubberisedbitumen binder Thus the crumb rubber addition led toimproving the binder resistance to oxidative aging

313 Softening Point Increment (Δ119878) The softening pointincrement can be used as a good indicator to measure thedegree of aging and it can be defined by Δ119878 and calculatedas shown in (4)

Δ119878 = SPaged minus SPunaged (4)

where Δ119878 is the softening point increment SPaged is agedsoftening point value and SPunaged is the unaged softeningpoint value Figure 5 shows the effect of crumb rubber

0

2

4

6

8

10

12

14

Δ119878

(∘C)

Crumb rubber content ()0 8 16

RTFOTPAV

Figure 5 Effect of aging on softening point increment of bitumenbinder

0500

10001500200025003000350040004500


1198772

= 0995

1198772

= 0891

1198772

= 0928

UnagedRTFOTPAV

119866lowast

sin

120575(P

amiddots)

Figure 6 119866lowast sin 120575 results versus crumb rubber content

modified binder bitumen on softening point changes afterRTFOT aging and PAV aging The softening point resultsof unmodified bitumen and rubberised bitumen showed anincrease after both aging conditions of RTFOT and PAVrespectively as the rubber content increased indicating thehardening level of the materials during aging In comparingthe softening point increment (Δ119878) of modified binder withbitumen without crumb rubber modifier the crumb rubbermodified bitumen showed lower (Δ119878) as rubber crumbcontent was increasedThis can be explained by the structuralchange of molecules in asphalt of fraction content duringaging which led to an increase in the softening point [17 18]Thus the results of using rubberised bitumen binder have asignificant effect on improving the aging resistance and showlower hardening aging which can reduce the oxidative agingresistance of the bitumen

314 Influence of Aging on Rheological Properties at 76∘CThe dynamic shear rheometer test was conducted to selectthe rutting resistance parameter119866lowast sin 120575 of the unmodifiedbinder and rubberised bitumenbinderweremastered at 76∘Cand the results are shown in Figure 6 Generally the higherrubber content led to high value of rutting factor 119866lowast sin 120575


0

05

1

15

2

25

3

35

4

Agi

ng in

dex

of119866

lowasts

in120575

RTFO PAV

CR 0CR 8CR 16

Figure 7 Aging index of 119866lowast sin 120575 of bitumen binder versus CRMcontent

for all combinations tested Additionally 119866lowastsin(120575) of agedrubberised bitumen was about 11 and 21 for rubbercontents of 8 and 16 compared to unaged base binderusing RTFOT aging conditionsThe increase in the119866lowastsin(120575)was about 38 and 60 for samples of 8 and 16 rubbercontent respectively compared to unaged base binder usingPAV aging conditions Thus the increase in crumb rubbercontent has an obvious effect on rutting factor 119866lowastsin(120575)with correlation coefficient 1198772 = 0995 In general the resultsof rubberised binder are in tandemwith the superpave binderspecification of a minimum 119866lowast sin 120575 requirement usingRTFOT (22 Pa) which showed that the binder with higher119866lowast

sin 120575 value is less susceptible to rutting deformation athigh pavement temperatures [10 19] Figure 7 shows theaging index of rutting factor119866lowast sin 120575 of original and crumbrubber modified bitumen binder at 76∘C as calculated by (5)as follows

AIRF =(119866lowast

sin 120575)aged(119866lowast sin 120575)unaged

(5)

In the case of AIRF as the aging index of rutting factor(119866lowast

sin 120575)aged and (119866lowast sin 120575)unaged is the 119866lowast sin 120575 valueof bitumen binder after and before aging respectively Theresults showed that119866lowast sin 120575 of bitumen binder with differentcontent of crumb rubber increased after different agingobviously after PAV aging Thus crumb rubber modifiedbitumen binder showed better resistance to oxidation agingAs displayed in Figure 7 the unmodified binder was of higherAIRFwhich led the binder to beingmore susceptible to agingwhile modified bitumen shows lower AIFR as crumb rubberincreased in the specimen leading to better aging resistanceof modified binder

Figure 8 shows the effect of aging on loss tangent ofbitumen binder after RTFOT aging and PVA aging Theresults displayed that the higher the crumb rubber contentthe higher aging index of loss tangent Tan 120575 indicating betteraging resistance The aging ratio of loss tangent is defined as

0

02

04

06

08

1

12

Agi

ng in

dex

ofta

n120575


CR 0CR 8CR 16

Figure 8 Effect of aging on Tan 120575 of bitumen binder

the ratio of aged Tan 120575 to unaged Tan 120575 of the bitumen binderas shown in (6)

Tan 120575 avg = [(Tan 120575)aged(Tan 120575)unaged

] times 100 (6)

where Tan 120575 avg is the average of Tan 120575 (Tan 120575)aged and(Tan 120575)unaged is the (Tan 120575) value of bitumen binder after andbefore aging respectively The higher value of aging indexTan 120575 is related to higher elastic behaviour (high in storagemodulus1198661015840) since Tan 120575 = 119866101584010158401198661015840 thus the high-loss tangentof rubberised bitumen led tomore elastic behaviour andmoresolid-like materialThis suggests that the rubberised bitumenbinder can improve the resistance to oxidative aging

32 Fatigue Cracking Properties at Intermediate TemperatureThe Strategic Highway Research Program (SHRP) had amaximum value of 5000 kPa for 119866lowast sin(120575) and low values ofthese parameters are considered good indicators of fatiguecracking resistance [16] In this study the fatigue resistanceparameter 119866lowast sin(120575) values of the unaged bitumen andrubberised binders after pressure aging vessel (PAV) weremeasured using the dynamic shear rheometer (DSR) at 31∘Cand the results are illustrated in Figure 9 In general the highcrumb rubber content led to lower 119866lowast sin(120575) values of therubberised bitumen binders The decrease in the 119866lowast sin(120575)was about 13 and 25 for rubber content of 8 and16 respectively after pressure aging vessel (PAV) agingconditions respectively Thus the increase in crumb rubbercontent has an obvious effect on aged rubberised bitumenfatigue parameter 119866lowast sin 120575 with correlation coefficient 1198772 =0816 after PAV aging Owing to the aging the results showedthat the lower the119866lowast sin 120575 value the less shearing energy lossand the better ability of the fatigue resistance Also119866lowast sin 120575 ofthe modified bitumen is lower than the unmodified bitumenat temperature of 31∘C indicating that rubberised bitumen


0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816


binder would improve the fatigue resistance of bitumen as aresult of introduction of crumb rubber modifier (CRM)

4 Conclusion

After the introduction to the problem a review of the liter-ature and analysis and discussion of the findings this sec-tion intends to summarise the overall conclusions achievedthrough this research Therefore the significant findings ofthe current study are as follows

(1) The results showed that the use of rubberised bitumenbinder reduced the aging effect on physical andrheological properties of the bitumen binder as illus-trated through lower aging index of viscosity loweraging index of 119866lowast sin 120575 at 76∘C and an increase inTan 120575 with increased crumb rubber modifier contentindicating that the antioxidant released in asphaltfrom the tire rubber particles is a significant factor inreducing the aging effect as correctly observed by thedata results

(2) In addition the results showed that the softeningpoint increment (Δ119878) and penetration aging ratio(PRA) of the rubberised bitumen binder decreasedsignificantly due to crumb rubber modification

(3) The aging index of viscosity reflected better resistanceof crumb rubber modified bitumen to aging as itshowed lower value after short-term aging RTFOTand long-term aging (PAV) respectively Thus theuse of viscosity index eliminated the variability causedby difference in viscosity of the original bitumen andmodified bitumen which provided a more reliablepicture of the hardening (aging) rate

(4) Furthermore the higher crumb rubber content thelower 119866lowast sin 120575 at 31∘C after PAV aging which led tohigher resistance to fatigue cracking

(5) Crumb rubber modifier increased the stiffness of thebitumen binder improving its resistance to rutting

References

[1] J C Petersen ldquoChemical composition of asphalt as related toasphalt durabilitymdashstate of the artrdquo Transportation ResearchRecord vol 999 pp 13ndash30 1984

[2] D R Brown D Jared C Jones and D Watson ldquoGeorgiarsquosexperience with crumb rubber in hot-mix asphaltrdquo Journal ofTransportation Research Record vol 1583 pp 45ndash51 1997

[3] G W Maupin Jr ldquoHot mix asphalt rubber applications inVirginiardquo Journal of Transportation Research Record vol 1530pp 18ndash24 1996

[4] E Charania J O Cano and R H Schnormeier ldquoTwenty-year study of asphalt rubber pavement in Phoenix ArizonardquoTransportation Research Board vol 1307 pp 29ndash38 1991

[5] M Stroup-Gardiner B Chadbourn and D E Newcomb ldquoBab-bitt Minnesota case study of pretreated crumb rubber modi-fied asphalt concreterdquoTransportation Research Record vol 1530pp 34ndash42 1996

[6] A A Mohamed O Husaini M O Hamzah and H IsmailldquoRheological properties of crumb rubber modified bitumencontaining antioxidantrdquo The Arabian Journal For Science andEngineering vol 34 article 1B 2009

[7] M Abdelaziz and M R Karim ldquoRheological evaluation ofageing properties of rubber crumb modified bitumenrdquo Journalof the Eastern Asia Society for Transportation Studies vol 5 pp820ndash833 2003

[8] S Liu W Cao J Fang and S Shang ldquoVariance analysis andperformance evaluation of different crumb rubber modified(CRM) asphaltrdquo Construction and Building Materials vol 23no 7 pp 2701ndash2708 2009

[9] S J Lee C K Akisetty and S N Amirkhanian ldquoThe effect ofcrumb rubber modifier (CRM) on the performance propertiesof rubberized binders in HMA pavementsrdquo Construction andBuilding Materials vol 22 no 7 pp 1368ndash1376 2008

[10] K D Jeong S J Lee S N Amirkhanian and K W KimldquoInteraction effects of crumb rubber modified asphalt bindersrdquoConstruction and Building Materials vol 24 no 5 pp 824ndash8312010

[11] L Raad and S Saboundjian ldquoFatigue behavior of rubber-modi-fied pavementsrdquo Transportation Research Record vol 1639 pp73ndash82 1998

[12] H R Soleymani H Zhai and H Bahia ldquoRole of modified bin-ders in rheology and damage resistance behavior of asphaltmixturesrdquo Transportation Research Record vol 1875 pp 70ndash792004

[13] S Aflaki and M Memarzadeh ldquoUsing two-way ANOVAand hypothesis test in evaluating crumb rubber modification(CRM) agitation effects on rheological properties of bitumenrdquoConstruction and Building Materials vol 25 no 4 pp 2094ndash2106 2011

[14] H U Bahia and D A Anderson ldquoGlass transition behavior andphysical hardening of asphalt bindersrdquo Journal of theAssociationof Asphalt Paving Technologists vol 62 pp 93ndash129 1993

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

[16] The Asphalt Institute Performance Graded Asphalt BinderSpecification and Testing Superpave Series (SP-1) LexingtonLexington Ky USA 2003

[17] P Cong S Chen J Yu and S Wu ldquoEffects of aging on theproperties of modified asphalt binder with flame retardantsrdquo


Construction and Building Materials vol 24 no 12 pp 2554ndash2558 2010

[18] M N Siddiqui and M F Ali ldquoStudies on the aging behavior ofthe Arabian asphaltsrdquo Fuel vol 78 no 9 pp 1005ndash1015 1999

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

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The applications of rubberised bitumen binders havereported many advantages for instance improved bitumenresistance to rutting due to high viscosity high softeningpoint and better resilience reduction in road pavementmaintenance cost lower fatiguereflection cracking and lesstemperature susceptibility [8] In general the applicationof crumb rubber modified in bitumen binder can improvebinder properties by lowering the inherent temperature sus-ceptibility of binders [9 10] The use of crumb rubber mod-ifier with bitumen binder led to enhancing the fatigue resis-tance [11 12] The improved performance of bitumen rubberpavements compared with conventional bitumen pavementsis primarily a result of improved rheological properties of therubberised bitumen binder

A study by Aflaki and Memarzadeh [13] investigated theeffect of rheological properties of crumb rubber on fatiguecracking at low and intermediate temperatures using differentshear methodsThe results of this study showed that the highshear blending indicated more influence on improvement oflow-temperature properties of rubberised binder than thelow shear blending The mechanism by which binder prop-erties may change at low temperature was presented Thismechanism is referred to as physical hardening occurringat temperatures next to or lower than the glass transitiontemperature and causes significant hardening of the bitu-men binder Aging influenced the bitumen chemistry andrheology significantly additionally the use of the two agingconditions that is thin film oven test (TFOT) and rollingthin file oven test (RTFOT) showed a strong correlation andsimilar severity [14] The ideal use of bitumen binders aspavingmaterials is dependent on its resistance to the physicalchange across the range of temperatures encountered in aconventional pavement Aging significantly changed both thechemical and physical properties of asphalts Physical prop-erties such as penetration ductility viscosity and stiffness areall affected to some extent by aging [15]

Aging indexmeasurement is one of themost popular pro-cedures used to determine aging susceptibility and providesranking of different bitumen binders Aging index is definedas the ratio of a given binder property after aging to thatproperty before aging as shown in (1)

Aging index =Bitumen property after agingsame property before aging

(1)

11 Research Objective and Scope The primary objective ofthis research is to evaluate and investigate the influence ofcrumb rubber content on the rubberised binderrsquos rheologicaland physical changes subsequent to aging The secondaryobjective is to identify the degree of aging in rheological andphysical properties of rubberised bitumen and its effect onhigh-temperature properties (rutting) as well as intermediatetemperature (fatigue cracking) through short-term aging test(rolling thin film oven test (RTFOT)) and long-term agingtest (pressure aging vessel (PAV))

Table 1 Physical and rheological properties of 80100 PG bitumen

Test properties ResultsViscosity at 135∘C (Pa sdot s) 065119866lowastsin 120575 at 64∘C (kPa) 135

Ductility at 25∘C (cm) gt100Softening point (∘C ) 47Penetration at 25∘C (d-mm) 88Ductility after RTFOT at 25∘C (cm) gt100RTFOT aged 119866lowastsin 120575 at 64∘C (kPa) 6022PAV aged 119866lowastsin 120575 at 25∘C (kPa) 31225

Table 2 The chemical components of the original bitumen beforeand after ageing

Unaged After RTFOT After PAVSaturates () 151 1388 1247Aromatics () 4855 4419 3855Resins () 2622 2894 3121Asphaltenes () 1013 1299 1777

Table 3 (CRM gradation)

Sieve 119899 (size mm) Particle size distributionNo 10 (200) 100No 16 (1180) 100No 20 (0850) 100No 30 (0600) 977No 40 (0425) 611No 50 (0300) 339No 80 (0180) 125No 100 (0150) 75No 200 (0075) 00

2 Experimental Program and Materials

The base 80100 penetration grade bitumen was used in thisstudy Tables 1 and 2 show the properties of base bitumenand the chemical components of original bitumen (beforeand after aging) respectively Rubberised bitumen binder wasprepared by mixing bitumen 80100 penetration grade withCRM (8 and 16 by binder weight) passing the 30 meshsieve as shown in Table 3 the propeller mixer used to mixthe base bitumen and the crumb rubber at constant blendingconditions of 180∘C temperature time of 60 minutes andvelocity of 200 rpm

The samples were aged using the standard rolling thinfile oven test (RTFOT) (ASTM D-2872) at a temperatureof 163∘C for 85min as short-term aging and pressure agingvessel (PAV) (AASHTO PP1) at 100∘C and an air pressureof 21Mpa for 20 hours to simulate the long-term aging Toinvestigate the influence of oxidative aging on rheologicalchanges of rubberised bitumen the age hardening is evalu-ated bymeasuring Brookfield viscosity (135∘C)ASTMD4402penetration test (25∘C) ASTMD5 softening point test (25∘C)ASTM D36 and dynamic shear (DSR) ASTM D-4 Proposal




Plate Dia(mm)



0500

100015002000250030003500400045005000

Visc

osity

at 1

35∘C

(MPa

middots)


UnagedRTFOTPAV

1198772

= 0999

1198772

= 0999

1198772

= 0992







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Visc

osity

at 1

35∘C

(MPa

middots)


CR 0CR 8CR 16


0

05

1

15

2

25

3Vi

scos

ity ag

ing

inde

x


CR 0CR 8CR 16



VAI =119881aged

119881unaged (2)



0

10

20

30

40

50

60

70

80

90

PAR

()


RTFOTPAV





) times 100 (3)





0

2

4

6

8

10

12

14

Δ119878

(∘C)


RTFOTPAV


0500

10001500200025003000350040004500


1198772

= 0995

1198772

= 0891

1198772

= 0928

UnagedRTFOTPAV

119866lowast

sin

120575(P

amiddots)





0

05

1

15

2

25

3

35

4

Agi

ng in

dex

of119866

lowasts

in120575

RTFO PAV

CR 0CR 8CR 16




AIRF =(119866lowast


(5)




0

02

04

06

08

1

12

Agi

ng in

dex

ofta

n120575


CR 0CR 8CR 16




] times 100 (6)




0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816



4 Conclusion







References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Plate Dia(mm)



0500

100015002000250030003500400045005000

Visc

osity

at 1

35∘C

(MPa

middots)


UnagedRTFOTPAV

1198772

= 0999

1198772

= 0999

1198772

= 0992







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Visc

osity

at 1

35∘C

(MPa

middots)


CR 0CR 8CR 16


0

05

1

15

2

25

3Vi

scos

ity ag

ing

inde

x


CR 0CR 8CR 16



VAI =119881aged

119881unaged (2)



0

10

20

30

40

50

60

70

80

90

PAR

()


RTFOTPAV





) times 100 (3)





0

2

4

6

8

10

12

14

Δ119878

(∘C)


RTFOTPAV


0500

10001500200025003000350040004500


1198772

= 0995

1198772

= 0891

1198772

= 0928

UnagedRTFOTPAV

119866lowast

sin

120575(P

amiddots)





0

05

1

15

2

25

3

35

4

Agi

ng in

dex

of119866

lowasts

in120575

RTFO PAV

CR 0CR 8CR 16




AIRF =(119866lowast


(5)




0

02

04

06

08

1

12

Agi

ng in

dex

ofta

n120575


CR 0CR 8CR 16




] times 100 (6)




0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816



4 Conclusion







References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

10

20

30

40

50

60

70

80

90

PAR

()


RTFOTPAV





) times 100 (3)





0

2

4

6

8

10

12

14

Δ119878

(∘C)


RTFOTPAV


0500

10001500200025003000350040004500


1198772

= 0995

1198772

= 0891

1198772

= 0928

UnagedRTFOTPAV

119866lowast

sin

120575(P

amiddots)





0

05

1

15

2

25

3

35

4

Agi

ng in

dex

of119866

lowasts

in120575

RTFO PAV

CR 0CR 8CR 16




AIRF =(119866lowast


(5)




0

02

04

06

08

1

12

Agi

ng in

dex

ofta

n120575


CR 0CR 8CR 16




] times 100 (6)




0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816



4 Conclusion







References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

05

1

15

2

25

3

35

4

Agi

ng in

dex

of119866

lowasts

in120575

RTFO PAV

CR 0CR 8CR 16




AIRF =(119866lowast


(5)




0

02

04

06

08

1

12

Agi

ng in

dex

ofta

n120575


CR 0CR 8CR 16




] times 100 (6)




0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816



4 Conclusion







References





























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0500

100015002000250030003500400045005000

119866lowast

sin

120575(k

Pa)


UnagedPAV

1198772

= 0847

1198772

= 0816



4 Conclusion







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



Research Article Investigations of Physical and Rheological...

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