Investigation of rutting performance of asphalt mixtures containing polymer modifiers

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    Tests used to assess the resistance of bituminous mixesto ow rutting are mainly the Marshall Test, the staticcreep test, the dynamic creep test, the wheel tracking test

    repeated loading, which leads to wheel track rutting, isprobably the most important requirement for perfor-mance-based specications. This is because a wide rangeof mixture parameters, not least those associated with theaggregate aects it. By contrast, elastic stiness and fatigueare principally controlled by binder characteristics and vol-

    * Corresponding author.E-mail address: aaksoy@ktu.edu.tr (A. Aksoy).

    Construction and Building Materi

    Construction1. Introduction

    Asphalt concrete mixtures have been exposed to greaterstresses because of the increasing trac volumes, trucktrac and higher tire pressures. Problems related to frac-ture; permanent deformation and surface wear are beingreported by user agencies in the worlds. One of the mostcommon forms of distress of asphalt concrete pavementsis rutting (permanent deformation). Rutting is the denedas the progressive accumulation of permanent deformationof each layer of the pavement structure under repetitiveloading [13].

    and the indirect tensile test. When used to study the resis-tance of bituminous mixtures to ow rutting, these testsprovide qualitative evidence to conclusions from eldobservations. Nevertheless, these tests are useful to com-pare alternative mix compositions from a qualitative pointof view; in addition, determination tests provide access tosome intrinsic mix properties, which can be used in the the-oretical and semi theoretical performance models [4].Detailed description of the models may reveal in the liter-ature [5].

    The implementation of a suitable test for assessing resis-tance to accumulated permanent deformation underAbstract

    The purpose of this study is to evaluate mechanical properties of control and modied asphalt mixtures. Conventional and ve mod-ied asphalt mixtures were studied on hot mix asphalt permanent deformation resistance. Amorphous polyalphaolen, cellulose ber,polyolen, bituminous cellulose ber and styrene butadiene styrene were used as modiers. Indirect tensile strength, indirect tensile, staticand repeated creep and LCPC wheel tracking tests were used for dierent loading conditions and temperatures. Research was focused oncomparing the interaction between LCPC wheel tracking and other mechanical tests. According to the LCPC wheel tracking andrepeated creep test results SBS mixtures were found as the most resistance mixtures in view of the rutting. Additives performed dierentperformance levels but showed more resistance to permanent deformation according to the conventional mixtures. As far as the staticcreep test results are concerned there are controversial results because conventional mixtures are better. It is thought that this result maystem from the static behavior of the load and rheological change of bitumen with modiers. 2005 Elsevier Ltd. All rights reserved.

    Keywords: Asphalt mixture; Rutting; Polymers; LCPC wheel tracking testInvestigation of rutting perfcontaining pol

    Sureyya Tayfur a, Halita ISFALT Asphalt Co

    b Department of Civil Engineering, Ylc Department of Civil Engineering, Karad

    Received 29 July 2004; received in revised foAvailable online0950-0618/$ - see front matter 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.conbuildmat.2005.08.014rmance of asphalt mixturesmer modiers

    zen b, Atakan Aksoy c,*

    any, Istanbul, Turkey

    Technical University, Istanbul, Turkey

    z Technical University, Trabzon, Turkey

    11 August 2005; accepted 12 August 2005November 2005

    www.elsevier.com/locate/conbuildmat

    als 21 (2007) 328337

    and Building

    MATERIALS

  • umetric proportions of the mixture and can be estimatedon the basis of past research for conventional materials.It was for these reasons that the uniaxial static creep testwas introduced in the 1970s. It is now recognized thatrepeated loading is a necessary requirement and, hence,the repeated load axial test has been developed at Notting-ham. This was done originally very much in the context ofmixture design [6].

    Besides laboratory tests, accelerated full-scale tests areworth noting. There are more than twenty full-scale testfacilities in the world (LCPC, CEDEX, IFT, ALF, etc.).

    mineral aggregate weight. It is added directly mixer inplant. BE was added 0.6% of total mixture weight. LikeSE, BE is added directly mixer in plant. PE is used in themixture between percent 0.4% and 1%. PE was used 0.6%of total aggregate weight. SB additive can be mixedbetween 3% and 7% of bitumen weight. In this study, SBwas added to bitumen 5%. Properties of the used modiersreveal in the literature [7]. All additives were dispersedhomogeneously in the mixture. It is not subjected occula-tion and mixing diculty for all the additives. Stone masticasphalt grain-size distribution was selected. Used SMAgradation values are given in Table 3 and gradation curveare represented in Fig. 1.

    Table 2The results of tests performed on asphalt cement (AC 6070)

    Test Method Unit Value

    Specic gravity (25 C) ASTM D-70 g/cm3 1.024Flash point (Cleveland) ASTM D-92 C 300Penetration (25 C) ASTM D-5 0.1 mm 64Ductility (25 C) ASTM D-113 cm 100+Heating loss-163 C % 0.05Heating loss Pen./original Pen. ASTM D-5 % 57.8Ductility after heating loss ASTM D-113 cm 51.5+Softening point ASTM D-36 C 55

    Table 3Gradation in this study and limits

    Sieve Sieve (mm) Passing (%) Lowerupper limits

    0.01 0.10 1.00 10.00 100.00Log Sieve Size (mm)

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    S. Tayfur et al. / Construction and Building Materials 21 (2007) 328337 329They make it possible to test full road structures con-structed and loaded like actual roads (materials, equip-ment, and loads). The object is most often to comparethe performance of dierent types of material, or the eectsof dierent construction techniques or loading modes.

    The main objective of this research study is to evaluateow-rutting properties and to compare creep test resultsas regard conventional and modied asphalt mixtures.

    2. Materials

    Used materials and experimental procedures in thisstudy are following. Aggregate combination, asphaltcement and ve dierent additives were used. Coarse aggre-gate was sampled from Corlu; ne-ller aggregate fromGebze in Turkey. Coarse aggregate is basalt in view of min-eralogy and ne-ller aggregate is old calcareous. Someproperties of coarse and ne aggregate were given in Table1.

    Regional factors were observed and 6070 penetrationasphalt cement produced from Yzmit Oil Renery (TUP-RAS) was used. Standard laboratory test results forasphalt cement are incorporated in Table 2.

    Five dierent additives were used. These additives areamorphous polialfaolen (AP), cellulosed ber (SE), cellu-losed ber mixed with bitumen (BE), poliolen (PE) andstiren-butadien-stiren copolymer (SB).

    AP takes parts in plastomer group. It has a granulartype and directly added to the mixture in mixer. It is addedabout percent 57 of bitumen weight. In this study, AP wasadded 6% of bitumen weight. Penetration value (100 g,5 sn, 25 C) is 1622, while softening point is 98110 Cand viscosity is 500012,000 MPa. SE was added 0.4% of

    Table 1Properties of coarse and ne aggregate

    Properties Test method Value

    Coarse aggregate

    L.A. abrasion (%) ASTM C-131 13.0Soundness in NaSO4 (%) ASTM C-88 4.47Flakiness (%) BS 182 (Part 105) 10.8Stripping resistance (%) ASTM D-1664 6070Water absorption (%) ASTM C-127 0.86Polishing value BS-813 0.60Fine aggregate

    Plasticity index Non-plastic1/2 in. 12.7 100 1003/8 in. 9.52 72.5 6580No. 4 4.76 30 2535No. 10 2 21.5 1825No. 40 0.42 15 1218No. 80 0.177 11.5 914No. 200 0.074 10 812

    80

    90

    100Fig. 1. Aggregate distribution on gradation chart.

  • Table 4Summary of Marshall design results

    NR AP

    Asphalt cement (%) 5.96 6.13Stability (kg) 675 650Bulk specic gravity (g/cm3) 2.474 2.472

    330 S. Tayfur et al. / Construction and BuilMarshall method (ASTM D1559) was used for deter-mining optimal bitumen content for conventional andmodied asphalt mixtures. Three identical samples wereproduced for all alternatives. Bitumen range region wasregulated according to the bitumen demand for eachmixture. Six designs were realized and 108 asphalt bri-quettes were fabricated. Compacting energy was appliedas 50 blows. The results of Marshall Test are presentedin Table 4.

    As it shown in Table 4 optimum bitumen content hasbeen increasing for modied mixtures. SE mixture hasthe highest bitumen content. Stability values for modiedmixtures has been increasing for SE, PE, BE and SB mix-tures but decreasing for AP mixtures. Marshall ows wereincreased for SE, PE, SB mixtures but decreased AP andBE mixtures. Voids lled with binder and voids lled withmineral aggregate values for modied mixtures wereincreased. The highest optimal bitumen content obtainedfrom Marshall Test was found in mixture with the cellu-lose ber. This is an expecting result because of wise spe-cic surface area and highly bitumen demand of cellulosebers. Void in mineral aggregate reached 17% for all mix-tures. This value is given a lowest limit for SMA mixtures.Even conventional mixture was reached that limit. It isunderstood that there is enough void for binder in themixture.

    SMA mixtures like porous asphalts are subjected bitu-men drainage problems. Because optimal bitumen contentis high drainage problems are concerned in mixing, trans-

    Void content (%) 4.20 4.10Flow (mm) 3.10 3.00Voids lled asphalt (%) 75.00 76.00Maximum specic gravity (g/cm3) 2.583 2.577Voids lled mineral aggregate (%) 16.95 17.20porting, laying processes. There is no an internationalaccepted drainage test but German Method, Binder drain-age test for gap graded mixtures and 2.36 mm sieve test aregenerally realized [7]. In this study 2.36 mm sieve and Ger-man Methods were used. The top limit in the tests isaccepted as 0.3%. Results are suitable for those criteria(see Table 5).

    Table 5Summarized binder drainage test results

    Type of mixing NR AP SE BE PE SB

    2.36 Sieve analysis 0.0 0.0 0.0 0.0 0.0 0.0German method 0.2 0.015 0.010 0.011 0.013 0.0163. Performance tests

    Conventional and modied mixtures were evaluatedwith the indirect tension strength test, indirect tension test,static creep test, repeated creep test and LCPC rutting test.Tests were realized at optimum asphalt content for allmixtures.

    3.1. Indirect tensile strength test

    The indirect tensile strength test is used to determine thetensile properties of the asphalt concrete which can be fur-ther related to the cracking properties of the pavement.This test is summarized in applying compressive loadsalong a diametrical plane through two opposite loadingstrips. This type of loading produces a relatively uniformtensile stress which acts perpendicular to the applied loadplane, and the specimen usually fails by splitting alongthe loaded plane [8].

    Test is the simple and Marshall Specimens may be used.Surface irregularities do not seriously aect the results andthe coecient of the variation of the test results is low [9].This test was applied at 25 C on briquettes both on con-ventional mixture and modied ones. Duration of the testload and deformation values was saved until breakingpoint. Poisson ratio was used as 0.35 like other researchersand calculated horizontal deformations [1013]. Variationof indirect tension strengths of the mixtures were illustratedin Fig. 2.

    SE PE BE SB

    6.98 6.50 6.60 6.69695 730 690 6902.440 2.450 2.468 2.4583.90 4.40 3.60 3.804.35 3.65 3.00 3.9079.00 76.00 79.00 79.002.546 2.564 2.560 2.55718.60 18.14 17.64 18.00

    ding Materials 21 (2007) 328337The typical values of the indirect tensile strength of spec-imens (18 Marshall Specimens) obtained from this studyranged from 683 to 917 kPa. Modied mixtures showedan increase in the tensile strength at 25 C. PE and SBmodied mixtures gave the highest strengths. Summarizedvalues are presented in Appendix A.

    The use of low density polyethylene (plastiphalt) asbitumen modier has been investigated and the resultsshow that an improvement in the quality of the binderand mix properties. The indirect tensile strength valueswere found to be much higher [14]. Low temperaturecracking, fatigue and rutting are three major distressesmechanism. Numerous researches have been conductedrelating the tensile strength of asphalt mixtures to the per-formance of asphalt pavements [15,16]. A higher tensile

  • good indicator of measuring permanent deformation forstone mastic asphalt mixtures.

    3.2. Indirect tensile test

    In recent years, there has been a change in philosophyin asphalt pavement design from the more empirical

    Building Materials 21 (2007) 328337 331strength corresponds to a stronger low temperature crack-ing resistance [17].

    In this study, the indirect tensile strengths of the modi-ed mixtures were also higher than the control mix. Thisindicates that the mixtures containing additives have highervalues of tensile strength at failure indirect tensile strengthunder static loading. This would further imply that modi-ed mixtures appear to be capable of withstanding largertensile strains prior to cracking. Conventional densegraded mixes normally combine high stability with lowow values and hence high MQ values indicating a highstiness mix with a greater ability to spread the appliedload and resist creep deformation. Care must be exercisedwith very high stiness mixes due to their lower tensilestrain capacity to failure, i.e., such mixes are more likelyto fail by cracking particularly when laid over foundationswhich fail to provide adequate support. Although the Mar-

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    Fig. 2. Indirect tension strength of the mixtures.

    S. Tayfur et al. / Construction andshall stability of the plastiphalt mix is much higher than thecontrol mix, the ow values of plastiphalt mixes are alsogreater indicating higher strain capacities to achieve failure.The value of MQ of the plastiphalt is higher than of thecontrol mix. It is well recognized that the MQ is a measureof the materials resistance to shear stresses, permanentdeformation and hence rutting [18].

    Internal resistances in hot mix asphalts were evaluated.This research indicated that the aggregate interlockinggreatly occurred in the coarse aggregate. The image evalu-ation of aggregate morphological characteristic demon-strated that a stable aggregate skeleton resulted in moreinternal resistance. Traditional tests such as Marshall Sta-bility and the indirect tensile strength were considered tobe inadequate to measure the internal resistance in HMA[19].

    Marshall Stability values were found generally higherthan the control mixtures. Only AP mixture gives lowerstability. AP and BE mixtures have lower ow value. Asfar as the Marshall test results are concerned for both con-trol and modied mixtures Marshall Quotient may not be aapproach to the mechanistic approach based on elastictheory. AASHTO in 1986, this mechanistic approach inthe form of elastic theory is being used by increasingnumbers of highway agencies. Elastic theory based designmethods require as input the elastic properties of pave-ment materials. Resilient modulus of asphalt mixtures,measured in the indirect tensile mode (ASTM D4123), isthe most popular form of stressstrain measurement usedto evaluate elastic properties. The resiliency modulusalong with other information is then used as input tothe elastic theories model to generate an optimum thick-ness design. Therefore the eectiveness of the thicknessdesign procedure is directly related to the accuracy andprecision in measuring the resiliency modulus of theasphalt mixture. The accuracy and precision are alsoimportant in areas where resilient modulus is used to asan index for evaluating stripping, fatigue and low temper-ature cracking of asphalt mixtures [13,20,21]. Indirect ten-sile tests were applied for both conventional and modiedmixtures. Variations of temperatures in the experimentswere used as 5, 25 and 40 C. Applied load was 1500 Nthat this load was nearly 20% of the indirect tensilestrength test at 25 C. Variation of the experiment param-eters were shown in Table 6.

    Pulse time was chosen 1000 ms for high tracked roadsvolume roads and 3000 ms for low tracked volume roads.Also vehicle speeds were observed and 40 ms rise time forhigh speed and 80 ms rise time for low speed were used.The average results of the resilient modulus are shown inFig. 3. Each value was obtained as 54 dierent resilientmodulus ratios [7]. Elasticity modulus values are the high-est at 5 and lowest at 40 C. These values are suitable withthe viscoelastic behavior.

    Resilient modulus values for mixtures were presented inFigs. 46. Average values were used for three identical bri-quettes for same mixture. While lower modulus values wereobtained at low temperature (5 C) higher modulus were athigh (40 C) for mixtures. Modied mixtures show morelow temperature cracking and rutting performance.

    According to the indirect tension test conventional mix-tures had higher elasticity modulus as 35% at 5 C that is

    Table 6Loading conditions for tests

    Loading period Rise time (ms)

    Frequency (Hz) Pulse period (ms)

    0.33 3000 40,60,80

    0.50 2000 40,60,801.00 1000 40,60,80

  • that mixtures had the lowest cracking resistance. Pulse timechanging (trac density) increased elasticity modulus asmuch as 8% for all temperatures while rise time (tracspeed) increased 25% especially at 25 and 40 C [7].

    From the earlier investigation indirect tensile stinessmodulus values tend to converge at 40 and 60 C for con-

    trol and modied asphalt mixtures [14]. Fig. 3 shows thesummarized indirect tensile stiness modulus results forboth the modied and control mixtures at 5, 25, 40 C.The results indicate that the stiness modulus values ofthe control mixtures especially at 5 C are higher than themodied mixtures but that at higher temperatures (25,40 C) the values tend to converge also.

    3.3. Static creep test

    Test has been used to determine permanent deformationof asphalt mixtures. Creep deformation of a cylindricalspecimen under a uniaxial, static load is measured as afunction of time, the sample dimensions and test conditionswere standardized. Deformation values were measuredwith time by a linear variable transformer (LVDT). Testwas carried out for all mixtures at the dosage of optimalbitumen. Because the permanent deformation risk wasmore under the heavy load and high temperature testparameters were selected: uniaxial load was 425 KPa(0.4 MPa), temperatures were 25 and 40 C, load durationwas 3600 s. The values of static creep compliance obtainedfrom the test are given in Figs. 7 and 8. Values were

    NR

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    5 25 40Temperature (oC)

    Res

    ilien

    t Mod

    ulus

    (MPa

    )

    Fig. 3. Average resilient modulus for all mixtures.

    332 S. Tayfur et al. / Construction and Building Materials 21 (2007) 328337Fig. 4. Resilient modulus for conventi

    Fig. 5. Resilient modulus for conventioonal and modied mixtures (5 C).nal and modied mixtures (25 C).

  • BuilS. Tayfur et al. / Construction andthought according to the SMA mixtures that had highlycreep modulus.

    The performance of exible pavements can be consid-erably be improved by using premium bituminous binders

    Fig. 6. Resilient modulus for conventio

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    Fig. 7. Time versus deformation in static creep test (25 C).

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    Fig. 8. Time versus deformation in static creep test (40 C).as prepared by modication. Unfortunately, the ruttingcalculation model in the present method does not cor-rectly predict the improvements in rutting behavior withabove premium binders. Measurements in the circularLTT in the Shell Research and Technology CentreAmsterdam show a considerable decrease in rutting forsuch modied binders, deviating from standard calcula-tions on the basis of static creep. The Shell PavementDesign Manual rutting method improved by replacingthe static creep curves by stiness relations as obtainedfrom dynamic laboratory test track tests. In contrast tothe static creep relations dierent relations are nowobtained for standard bitumen and premium binders.The slopes of such laboratory test track creep characteris-tics are much larger than found for the corresponding sta-tic creep tests [22]. According to the repeated creep andLCPC rutting test SBS modied mixtures show higherperformance than the others. There are controversialresults in view of the static creep tests especially for high(40 C) temperature as it shown in Figs. 7 and 8. It hasbeen suggested that static creep test does not reect the

    nal and modied mixtures (40 C).

    ding Materials 21 (2007) 328337 333performance of modiers, which improve the elasticrecovery of a materials, as well as repeated loading condi-tions [23].

    3.4. Repeated creep test

    Strength of the bituminous mixtures to the plastic defor-mation may be determined with the repeated creep test.Test equipment is the same as the static creep test butrepeated load are carried out dierently. Eciency of someselected chemical additives are especially evaluated with therepeated creep test also rutting investigation of SMA mix-tures are done. Experiments were realized at 25 and 40 Ctest temperatures during 1000 ms pulse period. Sampleswere exposed to 780 N (100 KPa) starting load. Average1100 N (138 KPa) load was put into practice during theduration of test. Loads and permanent deformations weresaved at least 20 h. For high temperature (60 C) repeatedcreep test failed because of the sample destruction.

  • Misleading results were obtained. Tests were realized at 25and 40 C. Figs. 9 and 10 shows the repeated creep curves.SB modied mixtures showed best result.

    Numerous investigations have been carried out onincorporating polymer modied bitumen to improve theperformance of bituminous composites. This included bitu-men modied with SBS or EVA or SBR (natural andground tyre rubber) in various concentrations. Most ofthe results obtained from laboratory and full-scale trialsdemonstrate to varying extents an improvement in the per-formance of these modied bituminous mixes in terms ofincreased resistance to permanent deformation, improve-ment in fatigue life, improved durability and resistance tomoisture damage [24,25].

    3.5. LCPC rutting test

    Rutting Test was veried with the LCPC method. Thistest has been used in France for over 20 years to success-

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    Fig. 9. Number of cycle versus permanent deformation (25 C).

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    Fig. 10. Number of cycle versus permanent deformation (40 C).

    334 S. Tayfur et al. / Construction and Building Materials 21 (2007) 328337Fig. 11. Asphalt mixture slabs afully prevent rutting in hot mix asphalt pavements. Inrecent years, the test has been used in the United States.Test is capable of simultaneously testing two HMA slabs.Slab dimensions are typically 180 mm wide, 500 mm long,and 20100 mm thick. Research indicates good correlationbetween LCPC test results and actual eld performance[26,27].

    Samples were prepared at 500 mm length mm width-100 mm height. Test temperature was 60 C. Samples werekept at least 12 h at that temperature. Each tyre wasapplied 5000 N load. Tyre pressure was 0.6 MPa (87 psi).Samples must be compacted as a determined degree ofcompacting. Test briquettes were compacted at 98% eldcompacting scale. Before the temperature was reached at60 C pre-compacting (1000 cycle) was made. Pre-condi-tioning temperature was regulated and values were saved.After the values were saved rutting was calculated. Twoidentical samples were used for each alternative (seeFig. 11).

    LCPC rutting test results for conventional and modiedmixtures are shown in Fig. 12. SBS mixtures show the high-est resistance to the permanent deformation and harmoni-ous results are concern with the repeated creep tests.fter the LCPC rutting test.

  • BuilIn general, it is believed that the higher asphalt contentsprovide the higher plastics ow susceptibility. The highlyplastic susceptibility may lead to the high permanent defor-mation, due to too much asphalt cement in the mix thatcauses the loss of internal friction between aggregate parti-cles and results in the loads being carried by the asphaltcement rather than the aggregate structure [28]. Reclaimedbuilding materials (RBM) for recycling are examined onhot mix asphalt permanent deformation performance.Four types of aggregates used for mixtures are: 100% rivercrush stone (CS), 100% reclaimed building materials(RBM), 50% coarse and ne RBM plus 50% coarse andne CS (50% RBM plus 50% CS) and, coarse RBM plusne CS (C-RBM plus F-CS). Two types asphalt cementAC-10 and AC-20 are used as a binder for mixtures. Thepermanent deformation test was performed by the wheeltracking device. Test was performed at 25 and 60 C.Apparently, the depths at 60 C indicate that the deforma-tion appears to be of plastic ow. Although RBM asphaltmixtures have higher asphalt contents than the CS mixturesthis is not the case of deformation following the above

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    Fig. 12. LCPC wheel tracking test results.

    S. Tayfur et al. / Construction anddescription. The phenomena may be explained by the factthat the high proportion of internal friction plays a mainrole in deformation resistance. However, the loss of inter-nal friction between aggregate particles at a high tempera-ture of 60 C is observed in 50% RBM plus 50% CSmixtures as the result of highest deformation happened.The asphalt cement either AC-10 or AC-20 used has no sig-nicant eect on the permanent deformation performance[29]. In this study, optimum asphalt contents for modiedmixtures are higher than the conventional mixture. Modi-ed mixtures reveal more resistance to the permanentdeformation in LCPC wheel tracking test at 60 C. It isthought that modiers contribute to adhesion ability todeformation resistance.

    4. Conclusions

    For the mixtures evaluated in this study the followingconclusions are derived. The indirect tensile strengths of the modied mixtureswere higher than the control mix. This indicates thatthe mixtures containing additives have higher valuesof tensile strength at failure indirect tensile strengthunder static loading. This would further imply thatmodied mixtures appear to be capable of withstand-ing larger tensile strains prior to cracking (internalresistance).

    Marshall stability values were found generally higherthan the control mixtures. Only AP mixture gives lowerstability. AP and BE mixtures have lower ow value. Asfar as the Marshall test results are concerned for bothcontrol and modied mixtures Marshall Quotient maynot be a good indicator of measuring permanent defor-mation for stone mastic asphalt mixtures.

    According to the indirect tension test conventionalmixtures had higher elasticity modulus as 35% at5 C that is that mixtures had the lowest cracking resis-tance. Pulse time changing (trac density) increasedelasticity modulus as much as 8% for all temperatureswhile rise time (trac speed) increased 25% especiallyat 25 and 40 C. The results indicate that the stinessmodulus values of the control mixtures especially at5 C are higher than the modied mixtures but thatat higher temperatures (25, 40 C) the values tend toconverge.

    It has been suggested that static creep test does notreect the performance of modiers, which improvethe elastic recovery of a materials, as well as repeatedloading conditions.

    SBS mixtures show the highest resistance to the perma-nent deformation and harmonious results are concernwith the repeated creep tests.

    In general, it is believed that the higher asphalt con-tents provide the higher plastic ow susceptibility.The highly plastic susceptibility may lead to the highpermanent deformation, due to too much asphaltcement in the mix that causes the loss of internal fric-tion between aggregate particles and results in theloads being carried by the asphalt cement rather thanthe aggregate structure. In this study, optimum asphaltcontents for modied mixtures are higher than the con-ventional mixture. Modied mixtures reveal more resis-tance to the permanent deformation in LCPC wheeltracking test at 60 C. It is thought that modiers con-tribute much to adhesion ability among aggregates ofhot asphalt mixtures.

    The type of asphalt modier does signicantly aect thepermanent deformation performance.

    Acknowledgements

    ISFALT Asphalt Company is gratefully acknowledgedfor their laboratory capabilities and possibilities. The

    ding Materials 21 (2007) 328337 335authors are also indebted to Mr. T. Erol for assistance inlaboratories.

  • Appendix 1. Summarized test results

    Modier NR AP SE PE BE SB

    Asphalt cement (%) 5.96 6.13 6.98 6.50 6.60 6.69

    Stability (kg) 675 650 695 730 690 690

    Bulk specic gravity (gr/cm3) 2.474 2.472 2.440 2.450 2.468 2.458

    Void content (%) 4.20 4.10 3.90 4.40 3.60 3.80

    Flow (mm) 3.10 3.00 4.35 3.65 3.00 3.90

    Voids lled asphalt (%) 75.00 76.00 79.00 76.00 79.00 79.00

    Maximum specic gravity (gr/cm3) 2.583 2.577 2.546 2.564 2.560 2.557

    Voids lled mineral aggregate (%) 16.95 17.20 18.60 18.14 17.64 18.00

    Indirect tensile strength test (Kpa) 683 701 799 917 805 898

    Indirect tensile test 5 C (lE) 7.830 9.883 10.311 10.426 10.620 10.0215 C (E) Mpa 20059.9 15623.2 14844.2 14762.8 14472.1 15392.925 C (lE) 48.164 45.233 47.152 43.463 44.000 40.79025 C (E) Mpa 3255.2 3436.0 3253.2 3496.8 3508.4 3765.440 C (lE) 220.310 176.692 213.972 198.630 206.734 158.61840 C (E) Mpa 707.9 875.6 720.1 772.0 752.4 976.0

    Static creep deformation (in./in.) 25 C 1 second 1187.5 1268 1113 1482 906 9253 second 1563.5 1742 1446 1884 1091 115810 second 2241.5 2649 2025 2592 1414 156330 second 3084.5 3826 2707 3456 1832 2070100 second 4097 5318 3503 4640 2411 27781000 second 5415 7293 4562 7012 3566 43373600 second 5778.5 7824 4890 7904 4073 5016

    Static creep deformation (in./in.) 40 C 1 second 2133 1973 2233 2585 1983 25033 second 2611 2431 2688 3186 2430 298210 second 3257 3096 3317 4086 3080 366830 second 3756 3660 3843 4900 3587 4284100 second 4180 4160 4356 5672 4041 49421000 second 4702 4744 5195 6712 4592 59853600 second 4921 4964 5659 7159 4814 6437

    Repeated creep deformation (in./in.) 25 C 1 pulse 186 149 447 312 206 903 pulse 638 553 1094 843 671 47510 pulse 1516 1353 1963 1624 1508 113230 pulse 2597 2360 2840 2353 2555 1850100 pulse 4023 3746 3992 3272 3973 27191000 pulse 6655 6316 6295 5345 6311 454210000 pulse 8336 7570 7968 6827 7470 613771706 pulse 9669 8301 10006 7653 8480 7115

    ******* NR AP SE PE BE SB

    Repeated creep deformation (in./in.) 40 C 1 pulse 384 414 820 662 466 1523 pulse 864 919 1569 1407 979 45610 pulse 1692 1769 2764 2509 1881 96930 pulse 2596 2704 3953 3615 2886 1531100 pulse 3542 3749 5122 4782 4001 21911000 pulse 5023 5171 6898 6599 5617 322110000 pulse 6592 6128 9236 7977 6761 395471706 pulse 9596 7139 17995 9331 8036 4517

    336 S. Tayfur et al. / Construction and Building Materials 21 (2007) 328337

  • Appendix 1 (continued)

    Modier NR AP SE PE BE SB

    LCPC wheel tracking deformation(rutting) 1000 cycle 3.15 3.30 3.02 1.98 2.85 1.643000 cycle 4.25 4.04 4.00 2.27 3.72 1.905000 cycle 5.08 4.53 4.72 2.61 4.26 2.1010000 cycle 6.82 5.22 6.07 2.65 5.18 2.2530000 cycle 9.14

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    Investigation of rutting performance of asphalt mixtures containing polymer modifiersIntroductionMaterialsPerformance testsIndirect tensile strength testIndirect tensile testStatic creep testRepeated creep testLCPC rutting test

    ConclusionsAcknowledgementsReferences

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