Workability and Performance of Polymer-modified Asphalt Aggregate Mixtures in Cold Regions

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  • This article was downloaded by: [University of Ottawa]On: 01 October 2014, At: 01:18Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

    International Journal of Pavement EngineeringPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/gpav20

    Workability and Performance of Polymer-modifiedAsphalt Aggregate Mixtures in Cold RegionsHannele K. Zubeck a , Lutfi Raad b , Stephan Saboundjian c , George Minassian d & P.E.John Ryer ea School of Engineering , University of Alaska Anchorage , Providence Drive, 99508,Anchorage, AK, USAb Transportation Research Center , Institute of Northern Engineering, University of AlaskaFairbanks , Fairbanks, AK, USAc Department of Transportation and Public Facilities Construction Section , Fairbanks, AK,USAd University of Alaska Fairbanks , Fairbanks, AK, USAe Department of Transportation and Public Facilities Construction Section , State of Alaska,Fairbanks, AK, USAPublished online: 11 Oct 2011.

    To cite this article: Hannele K. Zubeck , Lutfi Raad , Stephan Saboundjian , George Minassian & P.E. John Ryer (2003)Workability and Performance of Polymer-modified Asphalt Aggregate Mixtures in Cold Regions , International Journal ofPavement Engineering, 4:1, 25-36, DOI: 10.1080/1029843031000097535

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  • Workability and Performance of Polymer-modified AsphaltAggregate Mixtures in Cold Regions

    HANNELE K. ZUBECKa,*, LUTFI RAADb,, STEPHAN SABOUNDJIANc,, GEORGE MINASSIANd,{ and P.E. JOHN RYERe,

    aSchool of Engineering, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA; bTransportation Research Center,Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, AK, USA; cDepartment of Transportation and Public Facilities

    Construction Section, Fairbanks, AK, USA; dUniversity of Alaska Fairbanks, Fairbanks, AK, USA; eState of Alaska, Department of Transportation andPublic Facilities Construction Section, Fairbanks, AK, USA

    (Received 26 March 2001; In revised form 5 November 2002)

    Polymer-modified asphalts have been used in cold regions for about 15 years to address problems withrutting, cracking and premature aging. However, due to the cold climate and remote locationsconstruction problems are sometimes encountered. This paper deals with workability of polymer-modified mixes while assuring that the desired pavement performance is achieved.

    The construction problems arise with possible poor compatibility of the base asphalt and thepolymer, the storage stability of the asphaltpolymer mixture and cold construction temperatures.These properties were tested for several polymer-modified asphalt combinations. A set of products thatwere compatible, storage stable and had improved temperature susceptibility were selected and furthertested in asphalt-aggregate mixtures. A Georgia Wheel rutting test and the Thermal Stress RestrainedSpecimen Test were performed. A questionnaire study was also conducted to collect experiences andspecifications in cold regions.

    Tests indicate that polymer-modified asphalts should always be the end result of an extensive productdevelopment program. The polymer modification improved the performance of all base asphalts incertain polymerasphalt combinations. However, some otherwise acceptable binders smokedexcessively when the temperature was elevated to the recommended mixing temperature. This issuewarrants further investigation.

    Keywords: Low-temperature cracking; Rutting; Cold region; Polymers; Specifications

    INTRODUCTION

    Polymer-modification has been shown to reduce low

    temperature cracking and improve pavement performance

    (Raad et al., 1996; Lu and Isacsson 1997a). However,

    application of modified asphalt concrete is more

    expensive than traditional asphalt pavement. Therefore,

    it is important that the polymer-modified pavement is

    manufactured and constructed properly, assuring that the

    improvement in pavement performance and pavement life

    is achieved. Recently, there have been some problems

    constructing modified asphalt concretes in Alaska,

    particularly in obtaining required compaction levels, and

    roughness of the pavement surface.

    The goals of the research were to analyze modified

    asphalt cements in order to select binders with improved

    performance in the pavement when compared to

    traditional asphalt binders, while being able to be used

    in asphalt-aggregate mixtures without comprehensive

    difficulties in mixing, laying and compaction. In addition,

    the objective was to develop specification recommenda-

    tions for binder properties at the moment of application at

    a hot mixing plant, and to develop guidelines for the

    mixing and compaction temperatures.

    Approximately 40 different combinations of polymer-

    modified binders were mixed from 5 base asphalts and

    4 different polymers. Each of the combinations was tested

    for consistency, compatibility and storage stability. A mix

    design was conducted for testing the binders in asphalt-

    aggregate mixtures. At this phase, the binders were also

    evaluated qualitatively based on the handling properties of

    asphalt-aggregate mixture samples. The asphalt-aggregate

    ISSN 1029-8436 print/ISSN 1477-268X online q 2003 Taylor & Francis Ltd

    DOI: 10.1080/1029843031000097535

    *Corresponding author. E-mail: afhkz@uaa.alaska.eduE-mail: fflr@aurora.alaska.eduE-mail: steve_saboundjian@dot.state.ak.us{E-mail: saboundj@arsc.eduE-mail: john_ryer@dot.state.ak.us

    The International Journal of Pavement Engineering, Vol. 4 (1) March 2003, pp. 2536

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  • mixtures were tested in the Thermal Stress Restrained

    Specimen Test (TSRST) and Georgia Wheel Rutting Test

    (GWRT). A questionnaire study was also conducted to

    collect specifications from other cold regions. This paper

    covers the questionnaire study, gives the most popular

    specifications and summarizes the laboratory test results

    for a narrowed set of binders.

    QUESTIONNAIRE STUDY

    The purpose of the questionnaire study was to collect

    experiences, specifications and recommendations from

    agencies in cold regions. The emphasis of the study was to

    investigate possible constructability problems and factors

    such as compatibility causing these problems. The

    questions included in the questionnaire are given in

    Table I and the responders are given in Table II. The

    responses given are summarized in Tables III and IV.

    Use of Polymer-modified Asphalt Pavements

    Polymer-modified asphalts have been used in pavements

    from 2 to 15 years. In general, no specific constructability

    problems were reported. However, the mixing temperature

    at the hot mix plant was always higher when compared to

    the traditional mixes. Also, the effects of air temperature

    are more critical with polymer-modified mixes than

    traditional mixes. Most of the agencies specify the

    minimum air temperature. As an example, Quebec

    recommends 108C for the minimum pavement tempera-ture during the laydown. All responders were happy with

    the performance of the polymer-modified asphalts. Better

    performance was reported as decreased stripping and

    raveling, low temperature cracking, fatigue cracking and

    plastic deformation.

    Compatibility Studies

    Only the binder-suppliers and contractors reported that

    they study the compatibility of the polymers with asphalts.

    The responders that were agencies or road authorities

    reported that the investigation of the compatibility is the

    responsibility of the supplier and/or the contractor.

    Test Methods

    A variety of test methods is utilized in the characterization

    of the polymer-modified asphalts (Table IV). The most

    commonly used test methods were penetration at 258C,softening point (Ring & Ball), viscosity at various

    temperatures, storage stability, elastic recovery, fluo-

    rescent microscopic analysis and the Gel Permeation

    Chromatography (GPC).

    Materials used in Polymer Modification

    Only few of the responders reported the base asphalt

    sources and grades as well as the polymers used in the

    modified binders. The recipes are normally proprietary

    information of the supplier/contractor. The reported pene-

    tration grades for base asphalts varied from 85 to 300. The

    polymers used are also normally proprietary information,

    but Quebec, Finland and Japan reported that the styrene

    butadienestyrene (SBS) is the most commonly used

    polymer. Also, styrenerubber (SB) and styrenebuta-

    dienerubber (SBR) are used in the polymer modification

    of pavement asphalts by the responders. The modification

    degree is neither specified; however, the reported range

    varies from 2 to 7%. No major changes in the polymer types

    are predicted in the future by any of the responders.

    SUMMARY OF SPECIFICATION FOR POLYMER-

    MODIFIED ASPHALTS IN COLD REGIONS

    A summary of the specifications received for use in cold

    climates is given in Table V. Specifications from Idaho and

    Finland were attached with the questionnaire responses.

    The other specifications were obtained from various

    projects in the states mentioned (unpublished). Note also

    TABLE II Questionnaire responders

    Country or State Agency Responder

    Idaho DOT T. Baker, Materials EngineerQuebec DOT Pierre LangloisSweden VTI Ylva EdwardsSweden Nynas No name given, transmitted

    by Ylva EdwardsNorway Road Adm. Torbjorn JorgensenFinland Neste Oil Timo BlombergFinland VTT Laura ApiloSwitzerland EMPA Martin HugenerSaskatchewan City of Regina Carly LeMurrayJapan Ohbayashi Road Co. No name given, transmitted

    by Ishikawa Nishizawa

    TABLE I Questionnaire

    1 How many years have you been using polymer-modified bindersin asphalt pavements?

    2 Have you had notable difficulties with the constructability ofpolymer-modified asphalt pavements? If yes, how did you fixthe problem?

    3 In general, are you satisfied with the performance of polymer-modified asphalts? If no, why?

    4 Have you investigated the compatibility of the asphalt cementand the modifier?

    5 Which tests do you use in the characterization of the polymer-modified asphalts

    6 What sources of base asphalt are used in the polymer-modifiedbinders?

    7 What grades of base asphalt are used?8 Are these grades designed especially polymer modification in

    mind or for general use?9 Do you conduct chemical analysis on the base asphalts that are

    modified? If yes, which tests?10 Which polymers and specific grades have you used?11 Based on your experience, what is the optimal range for the

    polymer content? Specify for each polymer used, if it varies.12 Which polymers and specific grades will you use in the future?

    H.K. ZUBECK et al.26

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    PERFORMANCE OF PMAS IN COLD REGIONS 27

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  • that parts of the United States are already using or will be

    using the Superpave specifications instead of the

    specifications given here. As an example, the City of

    Regina, SK Canada uses Superpave PG grades 3454 and

    4060.

    All specifications given are end result specifications

    versus recipes including the base asphalt, polymer and

    modification level. However, the AASHTO (1992)

    specifications inform the user with which polymer the

    specifications will be met. The specifications attached

    with the questionnaire by Idaho, are recommended for hot

    climates according to the source, the AASHTO (1992)

    specifications.

    Most Popular Specifications

    Penetration at 258C is specified by every agency expectCalTrans. The specified penetrations vary from 50 to 160

    1/10 mm. Softening point (Ring & Ball) is also a popular

    specification. A common minimum value for the softening

    point is 608C. Viscosity is required by all agencies atvarying temperatures. A widely used maximum value for

    the viscosity at 1358C is 2000 mm2/s. Storage stabil

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