Performance evaluation of dense mixtures with stabilised rubber modified asphalt

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  • This article was downloaded by: [Nipissing University]On: 17 October 2014, At: 12:35Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

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    Performance evaluation of densemixtures with stabilised rubbermodified asphaltLitao Gengab, Xiaoying Wanga, Ruibo Rena, Faming Chenb & XinlongYangba Shandong Provincial Key Laboratory of Road and TrafficEngineering in Colleges and Universities, Shandong JianzhuUniversity, Jinan, People's Republic of Chinab Xinjiang Transportation Planning Surveying and Design Institute,Urumchi, People's Republic of ChinaPublished online: 19 Jun 2014.

    To cite this article: Litao Geng, Xiaoying Wang, Ruibo Ren, Faming Chen & Xinlong Yang (2014)Performance evaluation of dense mixtures with stabilised rubber modified asphalt, Road Materialsand Pavement Design, 15:4, 953-965, DOI: 10.1080/14680629.2014.924426

    To link to this article: http://dx.doi.org/10.1080/14680629.2014.924426

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  • Road Materials and Pavement Design, 2014Vol. 15, No. 4, 953965, http://dx.doi.org/10.1080/14680629.2014.924426

    Performance evaluation of dense mixtures with stabilised rubber modifiedasphalt

    Litao Genga ,b, Xiaoying Wanga, Ruibo Rena, Faming Chenb and Xinlong Yangb

    aShandong Provincial Key Laboratory of Road and Traffic Engineering in Colleges and Universities,Shandong Jianzhu University, Jinan, Peoples Republic of China; bXinjiang Transportation PlanningSurveying and Design Institute, Urumchi, Peoples Republic of China

    (Received 7 October 2013; accepted 9 May 2014 )

    Asphalt rubber (AR) has been used worldwide in road engineering not only for improvingthe performance of asphalt mixtures but also for providing an advantage in environmentalprotection. Yet the application of AR is greatly restricted in China for its shortcoming ofbeing only possible to be used in a gap or open gradation mixture to ensure stripping resis-tance as well as anti-rutting performance. Stabilised rubber modified asphalt (SRMA) withlower high-temperature viscosity and better store stability than traditional AR was developedin our previous research and has been widely applied in projects with good results. In thispaper, to evaluate the validation of SRMA in dense mixtures, five kinds of dense mixturescommonly used in China were designed with SRMA as binder. Engineering properties, includ-ing high-temperature performance, low-temperature performance, moisture stability, fatigueperformance and mechanical properties, including dynamic modulus and phase angle werelaboratory evaluated and analysed. For the purpose of comparison, a kind of representa-tive styrene-butadiene-styrene (SBS) polymer modified asphalt commonly used in China wasselected to prepare samples with the same gradation of SRMA mixtures, and the same perfor-mance tests were conducted. In addition, a brief cost analysis among SRMA, SBS-modifiedasphalt and traditional AR was performed. Results show good performance and economy ofSRMA and corresponding dense mixtures, thus it is possible, using SRMA for dense mixturedesign in practical engineering, to reduce construction cost.

    Keywords: stabilised rubber modified asphalt (SRMA); dense mixture; engineering proper-ties; mechanical properties

    1. IntroductionScrap tires have been a serious environmental problem throughout the world as they accumulaterapidly and are not easily disposed of (Fontes, Trichs, Pais, Pereira, &Minhoto, 2009). In order tominimise its impact, crumb rubber fromwaste tires has been used in asphalt modification resultingin asphalt rubber (AR) binders that have contributed to improving the mechanical properties ofasphalt mixtures (Kaloush, Witczak, & Way, 2002; Peralta et al., 2010; Lo Presti & Airey, 2013;Shatanawi, Biro, Naser, & Amirkhanian, 2013; Way, 2000; Willis et al., 2013). Since the early1970s, the Arizona Department of Transportation has used AR as a modified binder to reducereflective cracking in asphalt mixture rehabilitation overlays (Scofield, 1989; Sousa, Pais, Saim,Way, & Stubstad, 2001). AR has also been used to reduce maintenance and provide a smoothriding surface and good skid resistance. In addition, AR mixtures have been used to reduce noise

    Corresponding author. Email: glt@sdjzu.edu.cn

    2014 Taylor & Francis

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    mailto:glt@sdjzu.edu.cn

  • 954 L. Geng et al.

    in the tire-pavement interface (Zhu & Carlson, 1999). In China, to improve pavement service lifeand to conserve environment, the use of AR in asphalt pavement construction has been a commonpractice in recent years (Bai, Qian, &Cao, 2009; Cao, Ge, Zhou, & Lu, 2006;Wen&Yang, 2008).However, one of the main defects of AR is that crumb rubber and mastic asphalt are easy to

    segregate, which provides a very short time duration for asphalt mixture production and construc-tion after AR is produced. Observations also found that there was stripping in AR mixtures andravelling on the surface after freezing and thawing (Amirkhanian & Arnold, 1993; Doh, Park,Kim, & Kim, 2007b). To ensure enough stripping resistance and anti-rutting performance of ARmixtures, gap (or open) gradation and high asphalt binder content were commonly used for ARmixture design (Geng, Yang, Ren, & Wang, 2013), resulting in high construction cost as com-pared to conventional dense-graded mixture. Regretfully, there is no favourable subsidy for roadcontractors in China, and the further use of AR is largely restricted despite its merits in improvingpavement performance and environmental protection.On the other hand, much effort has recently been devoted to improving the performance of

    the AR (or crump rubber modified asphalt) mixtures (Doh, Park, Kim, & Kim, 2007a; Putman &Amirkhanian, 2006).Akindof crumb rubbermodified asphalt (producedwith petroleumasphalt asmastic asphalt, crumb rubber and certain aids) was developed in our former research and has beenapplied in a series of pavement projects in China with good results since 2009 (Ren, 2011). Thiskind of asphalt binder exhibited better store stability than AR. The basic production principle ofthis kind of rubber-modified asphalt is that physical and chemical reactions of desulphurisation,mixing and cross-linking occur in the crumb rubberasphalt system to obtain a stable colloidsystem under a specific production process. Our former research showed that even over twomonths hot storage, the technical properties of this kind of asphalt binder decayed slightly, andwe named it stabilised rubbermodified asphalt (SRMA). In our subsequent study, it was found thatthe high-temperature viscosity of SRMA was appropriately reduced to achieve better workableperformance without losing other performance by process adjustment.It is well known that the moisture stability of the asphalt mixture is related to its compaction

    degree, and the lower the high-temperature viscosity of the binder the higher the compactness ofthe asphalt mixture. As SRMA has lower high-temperature viscosity, and SRMA mixtures areeasier to compact than ARmixtures, designing dense mixtures with SRMA to achieve acceptablemoisture stability as well as to reduce construction cost will be possible.The purpose of this studywas to evaluate the validation of SRMA in densemixtures (traditional

    continuous dense-graded mixtures). Technical properties of SRMA were tested in the laboratoryand analysed first. Then two types of dense-graded asphalt mixtures AC-10 (including two kindsof gradations) and AC-13 (including three kinds of gradations) which are commonly used inChina were selected and designed using SRMA as a binder. Engineering properties, includinghigh-temperature stability, low-temperature performance, moisture stability, fatigue performanceand dynamic mechanical property were evaluated by laboratory experiments. During this study,a kind of representative styrene-butadiene-styrene (SBS) polymer modified asphalt commonlyused in China was selected as contrast sample. In addition, a brief cost analysis among SRMA,SBS-modified asphalt and traditional AR was performed. Results show good performance andeconomic advantage of SRMA and corresponding dense mixtures. Thus, it is feasible by usingSRMA for dense mixture design in practical engineering to reduce construction cost.

    2. Objective and scope of workThe objective of this study was to identify the validation of SRMA in dense mixture in thelaboratory.

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  • Road Materials and Pavement Design 955

    The scope ofwork in this research included a laboratory test for technical properties of SRMA inthe penetration grade system and in the performance grade (PG) system, mixture design and eval-uation of engineering and mechanical properties for two types of dense mixtures (total five kindsof gradations) mixed with SRMA. Meanwhile, a kind of representative SBS polymer modifiedasphalt was selected as contrast sample.

    3. Technical properties of SRMAIn this paper, SRMAwas produced with mastic asphalt of Qilu 70# road petroleum asphalt, crumbrubber and certain aids from a local entrusted asphalt plant in Jinan city, Shandong province. Forreasons of technical privacy protection, the detailed formula and production process of SRMAare not described here.Considering that SBS-modified asphalt is extensively used in road engineering in China, occu-

    pying about 80% market share of modified asphalt, a kind of commercial SBS-modified asphaltcommonly used in Shandong province was taken as the compared sample in this research. Tech-nical properties of factory-fresh SRMA, hot-stored for two months SRMA and SBS-modifiedasphalt were tested in the laboratory, and shown in Table 1. The technical performance of arepresentative AR (Wang, Li, & Lu, 2008) is also illustrated in Table 1.Test results of the technical properties of SRMA and SBS-modified asphalt samples shown in

    Table 1 indicate that: (1) both SRMA and AR show similar performance rather to that of SBS-modified asphalt, such as the smaller value of ductility and the bigger values of viscosity (135Cand 177C). (2) It is known that separation index is not a required item for AR because of its poorstorage stability and its production technology on site. But SRMA (fresh or hot-stored for twomonths) shows a rather satisfactory result in terms of separation, which is inferior to SBS-modifiedasphalt but superior to AR. (3) In addition, the high-temperature viscosities (135C and 177C)of SRMA are significantly lower than those of AR, showing its good workable performance.(4) There was no marked difference in technical properties between hot-stored and factory-freshSRMA samples. (5) the PG of PG 76-28 showed a wide climate applicability of SRMA.

    Table 1. Technical properties of SRMA, asphalt rubber and SBS-modified asphalt.

    Test results

    Factory- Hot-stored SBS-fresh SRMA Asphalt modified

    Test items SRMA (two months) rubber asphalt

    Penetration (25C), 0.1mm 67 65 63 57.5Ductility (5 cm/min, 5C), cm 17 17 11 24Softening point, C 58.9 58.0 60.0 67Flash point, C >300 >300 >300 >300Penetration index 0.094 0.089 0.121 0.170Rotational viscosity (177C), Pas 0.768 0.755 1.762 0.435Rotational viscosity (135C), Pas 3.960 3.850 5.221 1.506Elastic restitution (25C), % 83 80 68 89Separation, softening point difference (165C, 48 h), C 5.7 5.4 0.4Gravity (15C), g/cm3 1.0445 1.0445 1.0413 1.0283Thin film oven test (163C, 5 hr)Mass loss, % 0.12 0.15 0.23 0.32Penetration ratio (25C), % 73.85 75.37 67.42 85.04Ductility (5C), cm 9.5 10.0 4.4 16

    PG grade 7628 7628 7622

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  • 956 L. Geng et al.

    Table 2. PG test results of SRMA (hot-stored for two months) and SBS-modified asphalt.

    Test results

    Sample category Test item Temperature (C) SRMA SBS-modified asphalt

    Origin sample G/sin, kPa 82 1.871 1.58488 1.286 1.047

    Rolling thin film oven test sample G/sin, kPa 76 2.796 2.25582 1.755 1.492

    Gsin, kPa 19 432216 3945 668013 5730

    Pav sample Stiffness, MPa 18 189 18224 356 347

    m, MPa/s 18 0.313 0.32524 0.255 0.268

    Table 2 shows the PG test results of SRMA (hot-stored for two months) and SBS-modifiedasphalt. It can be seen that the high temperature PG grade of SRMA is PG 76, which is the samewith that of SBS-modified asphalt. But higherG/ sin values indicate the better rutting resistanceof SRMA. The smaller values of G sin of SRMA show better fatigue performance than that ofSBS-modified asphalt. And the similar S andm values between SRMA and SBS-modified asphaltillustrate their similar low-temperature performance.

    4. Marshall mix designThe aggregate used in this study is crushed limestone produced in Jinan city, Shandong provincein China. Physical properties of the aggregate, both coarse aggregate and fine aggregate togetherwith the mineral filler are given in Table 3. Two types of dense mixtures (total five kinds ofgradations) commonly used in Chinese practical projects were selected and the gradations arelisted in Table 4.In this study, SRMAhot-stored for twomonths was used for preparing asphalt mixture samples.

    SRMA binder contents were random chosen according to the experiential binde...

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