Fatigue performance evaluation of SBS modified mastic asphalt mixtures

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<ul><li><p>dJition</p><p>, Gw</p><p> High strain fatigue life of the SBS modied mastic asphalt mixtures was improved.exural toughness than control mixtures.</p><p>al in retarding fatigue crack growth.</p><p>thickness of asphalt concrete deck pavements is reduced by 50%,</p><p>life of the deck pavements [5,6]. Hence, high performance pavingmaterials needs to be developed for deck pavements in long-spanbridge decks.</p><p>Since 1960s mastic asphalt concrete pavements have been usedin European countries and Japan to enhance fatigue performance ofthe bridge deck pavements [7,8]. For example, 70 mm thick and50 mm thick mastic asphalt pavements have been used popularly</p><p>8.0%, resulting in superior durability and exibility. Also,h temperaely cooker</p><p>enables to maintain high temperature during productiotransportation. Due to superior uidity at the high tempemastic asphalt does not need a compaction procedure durconstruction; nonetheless, air void of the mastic asphalt concreteis almost close to zero.</p><p>In general, Trinidad Lake Asphalt (TLA) occupies 3050% ofasphalt binder in mastic asphalt mixtures. TLA is a high viscousnatural asphalt, providing higher durability, rut-resistance, andlow-temperature cracking resistance. In Germany and the Nether-lands, it is recommended to use the ratio of TLA to asphalt binder</p><p> Corresponding author. Tel.: +82 2 3408 3812; fax: +82 2 3408 4332.</p><p>Construction and Building Materials 48 (2013) 908916</p><p>Contents lists availab</p><p>B</p><p>evE-mail address: hlee@sejong.ac.kr (H.J. Lee).tensile strain at the bottom of the deck pavement can be doubledapproximately, resulting in considerable reduction of the fatigue</p><p>asphalt is mixed and constructed at a very higapproximately 230 C using a special mixer, nam0950-0618/$ - see front matter 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.conbuildmat.2013.07.100masticture ofwhichn andrature,ing theTLA (Trinidad Lake Asphalt)Bridge deck pavement</p><p>1. Introduction</p><p>Recently long-span bridges are constructed considerably in theworld. Orthotropic steel bridge decks have been popularly used forthe long-span bridges in order to reduce self weight of the bridgedeck [14]. The orthotropic steel bridge deck plate and deck pave-ments are designed as thin as possible, which leads to large deec-tions and to reduce fatigue life of deck pavements. For example, if</p><p>in Germany and the Netherlands, respectively. In Japan, a combina-tion of a 35 mm thick mastic asphalt base layer and a 35 mm thickmodied asphalt wearing surface layer has been applied to deckpavements. The main reason of the popular usage of the masticasphalt concrete in bridge deck pavements is that the masticasphalt could provide superior waterproong and higher exuralresistance than other deck pavement materials. Mastic asphaltpavements contain higher binder contents, typically more thanSBS (StyreneButadieneStyrene) modierFatigue performance The SBS modied mixtures had greater The SBS modiers was more substanti</p><p>a r t i c l e i n f o</p><p>Article history:Received 14 February 2013Received in revised form 23 July 2013Accepted 25 July 2013Available online 24 August 2013</p><p>Keywords:Mastic asphalta b s t r a c t</p><p>This study evaluated the fatigue performance of StyreneButadieneStyrene (SBS) modied masticasphalt mixtures used for bridge deck pavements. The effect of the type and content of newly developedSBS modiers was investigated using typical binder tests. Four-point bending beam fatigue and indirectstrength tests were conducted to examine fatigue and fracture behaviors of the SBS modied masticasphalt mixtures. The SBS modiers without C@C double bonds enhanced the mechanical properties ofthe mastic asphalt binder and mixtures: lower stiffness after short- and long-term oxidation, signicantlygreater fatigue resistance at a higher strain level, and higher crack development resistance.</p><p> 2013 Elsevier Ltd. All rights reserved. SBS modiers enhanced low-temperature crack resistance of asphalt binder.Fatigue performance evaluation of SBS mo</p><p>Tae Woo Kim a,b, Jongeun Baek a,b, Hyun Jong Lee b,,aHighway Pavement Research Division, SOC Research Group, Korea Institute of Construcof KoreabDepartment of Civil and Environmental Engineering, Sejong University, 98 Gunja-Dong</p><p>h i g h l i g h t s</p><p>Construction and</p><p>journal homepage: www.elsied mastic asphalt mixtures</p><p>Young Choi a</p><p>Technology, 2311 Daewha-Dong, Ilsan-Gu, Goyang-Si, Gyeonggi-Do 411-712, Republic</p><p>angjin-Gu, Seoul 143-747, Republic of Korea</p><p>le at ScienceDirect</p><p>uilding Materials</p><p>ier .com/locate /conbui ldmat</p></li><li><p>ble. SBS modied mastic asphalt mixtures have good fatigue</p><p>superior fatigue performance at a higher strain level of 1000 le</p><p>greater. The antioxidants were Irganox-1010 produced by Ciba and Irgafos 168 pro-duced by Gumho Petrochemical Co. The amount of the antioxidant ranged from0.4% to 5.0% by weight of the SBS modier where the antioxidants were usedequally.</p><p>Table 1Components of the ve types of SBS modiers.</p><p>ID SBS type Antioxidant content (wt.%)</p><p>SBS A SBS with C@C double bonds 0.4SBS B 1.0</p><p>SBS C SBS without double bonds 0.4SBS D 2.5SBS E 5.0</p><p>0</p><p>20</p><p>40</p><p>60</p><p>0.01 0.1 1 10 100</p><p>Pass</p><p>ing </p><p>(%)</p><p>Lower limit</p><p>Upper limit</p><p>This study</p><p>Building Materials 48 (2013) 908916 909or even greater [5,12].</p><p>2. Research objective and scope</p><p>In this study, SBS modied mastic asphalt mixture was devel-oped to enhance the fatigue resistance of conventional masticasphalt mixture where TLA is used as a part of asphalt binder. Inorder to evaluate the fatigue performance of the SBS modied mas-tic asphalt mixture, various laboratory tests for asphalt binder andmixtures were conducted. First, physical and mechanical bindertests were conducted to examine the characteristics of the SBSmodied asphalt binder and to determine the proper type and con-tent of the SBS modiers and TLA in the SBS modied mastic as-phalt mix design. The physical tests include penetration, ring andball temperature, and ductility tests before and after rolling thinlm oven aging. Second, four-point bending (FPB) fatigue testsand indirect tensile (IDT) strength tests were conducted to evalu-ated the fatigue resistance of the SBS modied mastic asphalt mix-tures in terms of fatigue life and crack development, respectively.</p><p>3. Experimental program</p><p>3.1. Materials</p><p>3.1.1. SBS modied asphalt binderControl asphalt binder consists of AC 60-80 base asphalt and 30% of TLA. In SBS</p><p>modied asphalt binder, a part of the TLA was substituted by SBS modiers to im-prove fatigue crack resistance. The type and content of the SBS modiers will bedetermined based on the performance of the SBS modied asphalt binder. Table 1lists the ve types of SBS modiers evaluated in this study.</p><p>The SBS modiers mainly contain SBS rubbers and antioxidants. Type A and BSBS modiers have double bonds (C@C) in molecular structures which can be bro-ken at a high temperature and result in thermal instability of the SBS rubbers. Intype C, D, and E SBS rubbers, the double bonds were cut by hydrotreating processperformance at a wide temperature range of 30 to 20 C [9,10].Thus, the use of the SBS is benecial to improve fatigue perfor-mance of mastic asphalt concrete. However, the use of modiedasphalt concrete in deck pavements led to the increase of initialconstruction cost. Life cycle cost (LCC) analysis showed that theLCC of modied asphalt concrete, Gussasphalt, mastic asphalt,and epoxy asphalt concrete could be lower than that of conven-tional deck pavements because of longer service life and lower usercost [11].</p><p>Mastic asphalt concrete is suitable for 5080 mm thick deckpavements [7]. Furthermore, thinner deck pavements, e.g.,40 mm or less, are needed for super long-span bridges as a wayof signicantly reducing self-weight of the deck pavements [6].Among several paving materials for long-span bridge deck pave-ments, SBS modied mastic asphalt concrete could be appropriatebecause of various types of SBS modiers and successful previousstudies. However, in order to apply the SBS modied masticasphalt concrete into relatively thin deck pavements, it requiresof 30% by weight; the ratio increased to 50% in the UK. Despite ofgood performance of the TLA, it is a natural product so that it is dif-cult to modify its original characteristics as required further.</p><p>Recently a couple of European countries led by Germany devel-oped StyreneButadieneStyrene (SBS) modied mastic asphaltbinders to improve the fatigue performance of mastic asphaltpavements. SBS is a synthetic rubber composed of three longchains of polystyrene, polybutadiene, and polystyrene which havecompletely opposite characteristics. Polystyrene is hard plastic tomake SBS durable at high temperature; polybutadiene behaves likea soft rubber at a room temperature leading SBS to be more exi-</p><p>T.W. Kim et al. / Construction and[13] to improve the high-temperature thermal stability. Also, two antioxidantswere added in the SBS modiers to mitigate the mastic asphalt from aging due tooxidation during mixing and transportation at a high temperature of 200 C or3.1.2. AggregatesAggregates used for the SBS modied mastic asphalt mixtures were based on</p><p>the Gussasphalt specications used in Germany and Japan [14,15]. The aggregateswhose nominal maximum aggregate size of 4.75 mm were used and consisted of46.5% of coarse aggregates, 30.0% of ne aggregates, and 23.5% of llers. Fig. 1shows the distribution of aggregates of the mastic asphalt mixture with upperand lower limits of Gussasphalt used in Japan [14]. In order to minimize the vari-ance of aggregate gradations, the quantity of aggregates was measured precisely(0.1 g) to meet the target gradation according to ASTM C136 [16]. The maximumpercentage of at and elongated particles whose dimensional ratio is greater than3:1 was limited to 10%, which is typically used for high-volume four-lane roadsin Korea.</p><p>3.1.3. Mix design for mastic asphalt mixturesIn this study, the mastic asphalt mixtures were manufactured as follows: rst</p><p>blended aggregates were heated up in a controlled-temperature oven at 200 Cfor at least 12 h. Asphalt binder was also heated up in another oven at 150 C for12 h. Then, the aggregates, asphalt binder, and TLA were mixed in a small-size coo-ker equipped with a self heating system that could control the cooker temperatureup to 300 C as shown in Fig. 2(a). It took approximately 20 min until the mixturetemperature reached the target temperature of 240 5 C. During the mixing, mix-ture temperature was periodically monitored and adjusted slightly to keep the tar-get temperature. For the SBS modied mastic asphalt, the SBS modiers were addedduring the mixing procedure.</p><p>A different mix design procedure was used for the mastic asphalt mixtures inorder to consider unique characteristics of the mastic asphalt mixtures, zero airvoids and no compaction. The Luer uidity, indentation, and wheel tracking testswere conducted on the control and SBS modied mastic asphalt mixtures to checkconsistency and rut-resistance at high temperatures. In the Luer uidity test, a 995-g weight was released to loosen 10-kg mastic asphalt mixtures at various temper-atures of 200260 C and penetration depth and time were periodically recordedduring the test as shown in Fig. 2(b). For each temperature, the penetration timevalue corresponding to 5 cm of penetration was determined. The mastic asphaltmixtures can be mixed and placed properly if the penetration time is in the rangeof 420 s.</p><p>The indentation test [17] was performed to measure indentation depth of a 7-cm3 cubic specimen by a 52.5-kg rod at 40 C during 30 min as shown in Fig. 2(c). Ifthe indentation value ranges 14 mm, the mastic asphalt is regarded to be stable atthe high temperature. The wheel tracking test [18] was also conducted to measurerut depth by repeated wheel loads at 60 C as shown in Fig. 2(d). Deformation of a</p><p>80</p><p>100Seive size (mm)Fig. 1. Particle size distribution for the mastic asphalt mixture.</p></li><li><p>er </p><p>910 T.W. Kim et al. / Construction and Building Materials 48 (2013) 908916specimen under 686 N of the wheel load was recorded and the number of load rep-etitions per 1 mm of deformation was computed as dynamic stability. The mini-mum dynamic stability for mastic asphalt mixtures is typically 300 cycles/mm.</p><p>Based on the mix design test results for various contents of asphalt binder, SBSmodier, and TLA, the optimum SBS modied asphalt binder content was deter-mined as 8.3% by weight of the mixture which includes 15% of TLA and 8.5% ofSBS modier by weight of the asphalt binder. On the other hand, the asphalt binderin the control mastic asphalt mixture was 8.5% by weight of the mixture where 30%of TLA by weight of the asphalt binder was used. Table 2 shows the contents of baseasphalt, SBS, and TLA and mix design test results.</p><p>3.2. Laboratory tests</p><p>3.2.1. Asphalt binder testsA series of physical and mechanical binder tests was conducted on the control</p><p>and ve SBS modied asphalt binders to evaluate the effect of the SBS modier onthe behavior of the asphalt binder in terms of penetration, softening point, ductility,and stiffness before and after short-term and long-term aging. The rolling thin lmoven (RTFO) and pressure aging vessel (PAV) tests were used to simulate the short-term and long-term aging of the asphalt binder. In addition, the morphology of theSBS modied asphalt binder was investigated using optical microscopy.</p><p>Fig. 2. Laboratory test setup for mix design: (a) the cooker, (b) the Lu3.2.2. Mixture testsIn this study, fatigue crack resistance of the mastic asphalt mixture was the</p><p>main concern because fatigue cracking has been considered as the main failure cri-terion for deck pavements [19]. The fatigue performance of the mastic asphalt mix-tures was evaluated using four-point bending (FPB) fatigue tests [20,21]. Inaddition, crack resistance was evaluated using FPB and indirect tensile (IDT)strength tests.</p><p>The FPB fatigue tests were performed at a frequency of 10 Hz and at a temper-ature of 20 C under the controlled-strain mode of loading which is more preferredfor thin exible pavements such as bridge deck pavements where the elastic recov-ery properties of the material can affect its fatigue life [22]. Only a minor permanentdeformation could be developed in the specimen during the fatigue tests since thestrain applied to the specimen must be recovered to the original position in each</p><p>Table 2Mix design test results for the control and SBS modied mastic asphalt mixtures.</p><p>Asphalt binder Control</p><p>AC (%)a 8.5Component Base SBSContent (%)a 70.0 0.0</p><p>Test Targetb</p><p>Fluidity time (sec) 420Indentation depth (mm) 14Dynamic stability (cycles/mm) &gt;300</p><p>a Asphalt binder and component contents are represented by weight of the mixture ab The target values were adapted from previous studies [4,14].cycle. Initial exural stiffness of a beam specimen (380 mm long 63 mmwide 500 mm high) was calculated at the 50th loading cycle. According to ASTMD7460-10 testing standard, fatigue failure is dened as the number of loading cy-cles when the initial stiffness is reduced by 50%. In this study, however, the 60%of stiffness reduction wa...</p></li></ul>

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