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Construction and Building Materials 62 (2014) 1–7
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Construction and Building Materials
journal homepage: www.elsevier .com/locate /conbui ldmat
Influence of SBS and asphalt on SBS dispersion and the performanceof modified asphalt
http://dx.doi.org/10.1016/j.conbuildmat.2014.03.0180950-0618/� 2014 Elsevier Ltd. All rights reserved.
⇑ Corresponding author. Tel.: +86 13801017308.E-mail addresses: [email protected] (F. Dong), [email protected] (W. Zhao),
[email protected] (Y. Zhang), [email protected] (J. Wei), [email protected] (W. Fan), [email protected] (Y. Yu), [email protected](Z. Wang).
Fuqiang Dong, Wenzhe Zhao, Yuzhen Zhang ⇑, Jianming Wei, Weiyu Fan, Yanjie Yu, Zhe WangState Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao, Shandong Province 266580, PR China
h i g h l i g h t s
� High aromatics and low asphaltenes could improve dispersion of SBS.� Particle size distribution curve S/B ratio at 30/70 was narrower than others.� As SBS contents increasing the particle size distribution curve became wide.� With the range of SBS distribution becoming narrow the viscosity was increased.
a r t i c l e i n f o
Article history:Received 10 December 2013Received in revised form 9 March 2014Accepted 11 March 2014
Keywords:Asphalt componentsSBS structureParticle size distribution of SBSImage-Pro Plus programSBS modified asphalt
a b s t r a c t
Styrene–butadiene–styrene (SBS) modified asphalt (PMA) was prepared by high shear method. Fourasphalts with different components and four types of SBS copolymers with different S/B ratio and typeswere selected in this study. The influences of the asphalt components and SBS structure as well as SBScontents on the particle size distribution of SBS and properties of the SBS modified asphalt wereinvestigated. Fluorescence microscope and the Image-Pro Plus program were chosen to characterizethe microstructure and count the particle size distribution of SBS. The results show that the asphaltcomponents, SBS structure and content had significant impacts on the particle size distribution of SBSpolymer in asphalt and the performance of SBS modified asphalt. The high aromatics content and thelow asphaltenes content could improve the dispersion of SBS in asphalt. When the S/B ratio is 30/70,the particle size distribution curve was the narrowest and the performance of modified asphalt wasimproved. With the content of SBS increasing, the particle size distribution curve became wide and thesoftening point of the modified asphalt was increased, while the penetration and the ductility weredecreased. The viscosity at 135 �C of modified asphalt was increased with the range of the particle sizedistribution curves becoming narrow.
� 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Asphalt is a residue of crude oil refining, described as a mixtureof various chemical components. Despite its complicated composi-tion, asphalt is a well-known natural material and widely used inroad pavement as the binder of aggregates [1,2]. Unfortunately,further applications of asphalt are restricted by some disadvan-tages, such as high-temperature rutting and low temperaturecracking [3]. In order to improve the quality of asphalt, it isgenerally modified by various polymers such as styrene–butadi-
ene–styrene (SBS) block copolymers, styrene–butadiene rubber(SBR), and ethylene–vinyl acetate (EVA) [4,5]. The most commonlyused polymers belong to the group of thermoplastic elastomericblock copolymers and SBS especially seems to be a useful modifierof conventional asphalt [6–8]. It is known that SBS block copoly-mer can improve both the low and high temperature propertiesof asphalt [9]. Recently, some research [10–13] focused on the con-ventional properties, aging properties, rheological properties,mechanism and microstructure of SBS modified asphalt as wellas the manufacturing process.
However, there are some problems for SBS modified asphalt,such as difficulty for quality control and lack of storage stability,which are probably attributed to the different microstructure ofSBS modified asphalt. Some published works [14–19] have studiedthe relationship between morphology and performance of SBSmodified asphalt. The fluorescent microscope, image collecting
Table 2Properties of SBS copolymers.
Items Unit Copolymer
1201 1301 1401 4303
Structure Linear Linear Linear RadialStyrene–butadiene ratio 20/80 30/70 40/60 30/70Average molecular weight 104 g/cm�3 10 10 9.5 28Shore hardness A P58 70 92 82Tensile strength MPa 8 25 36.5 14300% Tensile stress MPa 1.4 2.55 3.86 2.0Breaking elongation % 700 915 755 650Volatile matter % 0.7 0.7 0.7 0.7Ash content % 0.2 0.2 0.2 0.2Melt flow rate g/min 0.1–5 0.1–5 0.5–5 0–1.0
2 F. Dong et al. / Construction and Building Materials 62 (2014) 1–7
system, and professional software were used to qualitativelyanalyze the microstructure of SBS modified asphalt, in which theanalysis method of microstructure was established. However, themicrostructure was not analyzed quantitatively and the factors ofinfluencing on the SBS modified asphalt morphology have not beeninvestigated systematically. It is known that SBS is a block copoly-mer of styrene and butadiene, which has different structures, blockS/B ratio, and molecule weights. Furthermore, asphalts are extre-mely complex and variable materials, the properties of which de-pend not only on the crude oil used to obtain the asphalt, butalso on the refining process itself. Therefore, it is necessary toinvestigate the influence of asphalt chemical composition andSBS structure on the morphology and properties of SBS modifiedasphalt for understanding on the interaction of polymers with dif-ferent asphalts better.
The objective of the current study was to investigate the effectsof asphalt source/grade, the SBS content and structure on theparticle size distribution of SBS and properties of the SBS polymermodified asphalt using conventional methods and fluorescencemicroscope observation.
2. Experiment and methods
2.1. Materials
Four asphalts (penetration grade AH-70 and AH-90) were used to prepare anumber of laboratory modified asphalt samples. They were coded as ZH AH-90,QHD AH-90, QHD AH-70, and LH AH-70, respectively. The properties of the fourbase asphalts are presented in Table 1.
Four kinds of SBS were selected in this study, which were denoted as 1201,1301, 1401, and 4303. The 1201, 1301 and 1401 are linear SBS polymers containing20%, 30%, and 40% styrene, respectively. And the average molecular weights are allabout 100,000 g/mol. 4303 is a radial SBS polymer with 30% styrene and the averagemolecular weight is about 280,000 g/mol. Table 2 lists the basic properties of thefour SBS copolymers.
2.2. Preparation of SBS polymer modified asphalt samples
SBS polymer modified asphalt samples (SPMA) were prepared with four baseasphalts and four SBS polymers with different loading levels (1%, 3%, and 5% byweight of modified asphalt) by mechanical mixing using a high shear mixer.According to the previous study in our group [24], the following preparation proce-dure of SBS modified asphalt was followed. The asphalt was heated to become afluid in an iron container, then upon reaching about 170 �C, a certain amount ofSBS was added into asphalt, and after reaching 175 �C, the mixture was blendedat 3000 r/min for 60 min. After completion, the SPMA was removed from the ironcontainer and stored for further tests.
2.3. Test methods
2.3.1. Conventional asphalt testsThe SBS modified asphalts were subjected to the following conventional asphalt
tests: softening point, penetration, and ductility test. The softening points (ring andball test) were measured according to GB/T 4507. Penetration tests were carried at25 �C according to GB/T 4509. And ductility was determined at 5 �C on the basis ofGB/T 4508.
Table 1Properties of four base asphalts.
Items ZH QHDAH-90 AH-90
Softening point (�C) 45.0 44.9Penetration (25 �C, 0.1 mm) 86 86Ductility (25 �C, cm) >150 >150
Content of componentsSaturates (S)/% 23.3 17.21Aromatics(A)/% 35.0 42.56Resins (R)/% 35.4 21.08Asphaltenes (At)/% 6.3 14.36
2.3.2. Rotational viscosity testThe modified asphalt needs remain sufficiently fluid or workable at high
temperatures, so that the energy required during the plant mixing, laydown, andcompaction phases is minimized. The rotational viscometer measures the viscosityof modified asphalt to evaluate the workability during mixing and compaction pro-cesses. In this study, the Brookfield viscometer equipped with a thermo containerfor control of sample temperature was used to measure the dynamic viscosity ofthe prepared samples at 135 �C.
2.3.3. Chemical compositionIn order to know the relationship between the asphalt components and the per-
formance of the modified asphalt, the chemical composition (saturates, aromatics,resins, and asphaltenes) of asphalt was determined according to SH/T0509-2010.
2.3.4. Morphology of the SPMAIn order to describe the microstructure interacting between asphalt and
polymer, the term ‘‘morphology’’ is often used [25]. A fluorescence microscopeFM-400 was utilized to observe the morphology of the SPMAs. The state of SBSdispersion in the base asphalt can be determined. And the continuous and discon-tinuous phases can be characterized as well. It has been proved that this techniqueis the most valuable method to study the morphology of the polymer modified as-phalt [14–16,26].
Due to the fluorescent effect of the SBS copolymer, the SBS modified asphalt canbe illuminated using blue light for excitation, and then the fluorescent yellow lightre-emitted by the polymer phase is observed under an optical microscope [27].
SPMA samples for the morphology analysis were prepared using the followingpreparation method. After the modified sample was prepared, a glass rod was usedto dip into the sample immediately and one drop of it was put in the centre of aglass slide. Then, this drop was covered by a piece of cover glass. In order to obtainsmooth surface of the sample for nice observation, the covered sample was heatedup to 135 �C at a certain heating rate in an oven, and a translucent film was formedon the glass slide after about 10 min. After this, the film covered with a cover glasswas cooled down to the room temperature. And then, the samples were viewed un-der the microscope with a magnification of 400 at room temperature. Images werethen recorded by a digital camera (fitted in line with the optic axis of the micro-scope by means of an attachment to the trinocular observation head), as shownin Fig. 1(a). The camera digitized the image and stored the data as an image filein the permanent memory of a workshop.
2.3.5. Image-Pro-Plus processing and analysisImage-Pro-Plus analysis program has been applied to extract significant infor-
mation from the captured images to determine the particle size distribution of poly-mer, catalysts and other civil engineering materials [14,26]. In this paper, the imageprocessing and analysis were used to quantify particle size distribution of SBS in theSPMAs.
QHD LH Test methodsAH-70 AH-70
48.5 48 GB/T 4507 [20]67 68 GB/T 4509 [21]>150 >150 GB/T 4508 [22]
19.07 20.18 SH/T 0905 [23]39.85 39.1827.19 28.6214.17 10.96
Fig. 1a. Fluorescent images of SBS PMA samples with 400 magnifications (original).
Fig. 2. Influence of asphalt types on particle size distribution of SBS.
F. Dong et al. / Construction and Building Materials 62 (2014) 1–7 3
After the images had been captured by digital camera, they were transformed togray scale as shown in Fig. 1(b). Using the algorithms within the Image-Pro-Plusprogram, operations including shading corrections, contrast/brightness optimizing,white top hat (function to enhance the white detail and to remove the unwanted arteffects), and sharpen, enhancement were then applied to transform the originalimage to binary image. The main purpose of this step was to isolate polymers fromcomposite images, therefore to prepare the images that were ready for quantifiedmeasurements. Fifty different images of one sample were analyzed together in or-der to improve the veracity of the obtained results.
3. Results and discussion
3.1. Influence of asphalt components on particle size distribution of SBSand the properties of SBS modified asphalt
In this section, the 1301 SBS was selected to complete theexperiments due to its large amount usage in the domestic market.The SBS loading level was 3% by weight of the modified asphalt.The preparation parameters are referred to Section 2.2.
The particle size distributions of SBS in modified asphalts aregiven in Fig. 2. It is observed that the range of SBS particle size dis-tribution in modified asphalt LH AH-70 and QHD AH-90 was nar-rower than that in the modified asphalt QHD AH-70 and ZH AH-90.
As we all known that asphalt is extremely complex and vari-able, depending on the source of the crude oil from which the as-phalt originates and modification induced by treatments in therefinery. And SBS is a block copolymer of styrene and butadiene.So the compatibility of SBS and asphalt is important for themicrostructure and performance of SBS modified asphalt.
Fig. 1b. Fluorescent images of SBS PMA samples with 400 magnifications.
However, the compatibility of SBS and asphalt depends on theircompositions. Therefore, investigating the influence of chemicalcomposition and physical properties of asphalt on SBS modifiedasphalt, especially for different base asphalts, could help to havea better understand on the interaction of polymers with differentasphalts.
Cavaliere et al. [28] stated that when SBS was blended with as-phalt, the elastomeric phase of SBS copolymer would absorb the oilfractions from the asphalt and swell up to nine times as much as itsinitial volume. Some researchers [29] showed that the contents ofaromatics in asphalt played a significant role in compatibility be-tween asphalt and polymer, and the higher contents of aromaticswas, the better modified asphalt performed. Meanwhile, asphalt-enes is an important part in asphalt, less lead to a better dispersionof polymer but the high temperature performance of modified as-phalt decreases; it prevents the polymer becoming small particleas an obstacle and the low temperature performance of modifiedasphalt also decreases if its content is sufficient. Kamiya [1]showed that maltene, the soluble fraction extracted from asphaltby n-heptane, could interact preferentially with the poly-butadi-ene unit of SBS, whereas asphaltene, the insoluble fraction wouldinteract predominantly with the poly-styrene unit. Above all, itshould be concluded that the distribution of polymer in modifiedasphalt closely related to contents of aromatics and asphaltenes.Furthermore, the high aromatics content and the low asphaltenescontent could improve the dispersion of SBS.
The properties and components of the four asphalts are pre-sented in Table 1. It is important to underline that the contentsof aromatics and asphaltenes are different among them, and thecontents of aromatics and asphaltenes in QHD AH-90, QHD AH-70 and LH AH-70 asphalts are higher than that in ZH AH-90 as-phalt. The four components of asphalts have absolutely differentinteraction with the polymer and it is found that asphaltenes arealways less prone to be mixed. As shown in Fig. 2, asphalt compo-nents have great influences of the dispersion of SBS in asphalt.When the content of asphaltenes is a constant, the particle sizedistribution of SBS is becoming narrower as aromatics contentincreases. For example, the range of distribution of SBS in QHDAH-90 asphalt is narrower than that in QHD AH-70 asphalt.Meanwhile, when the content of aromatics is a constant, the rangeof SBS distribution is becoming wider as asphaltenes contentincreases. It is shown the curve of QHD AH-70 is wider than thatof LH AH-70. However, when the content of aromatics is too low,the range of SBS distribution is also wider even though the asphalt-enes content is low such as ZH AH-90 asphalt.
4 F. Dong et al. / Construction and Building Materials 62 (2014) 1–7
It is known that the chemical composition of asphalt affects theproperties of SBS modified asphalt. Fig. 3 illustrates the influence ofasphalt components on the properties of SBS modified asphalt. SBSmodification caused increases in both softening point and ductilityat low temperature, and reductions in penetration. Notably, thereare great differences in properties of SBS modified asphalt pre-pared by different types of asphalt [1,30]. As for the different gradeof asphalt, the softening point of modified asphalt prepared by AH-90 asphalt is lower than that of AH-70 asphalt. On the contrary,penetration at 25 �C and ductility at 5 �C of modified asphalt pre-pared by AH-90 is higher than that of AH-70 asphalt. As for thesame grade asphalt, the soften point of SBS modified asphalt de-crease as aromatics content increases. While the contents of aro-matics are similarly, the soften point and viscosity of SBSmodified asphalt increase as asphaltenes content increases. The re-sults indicated that the high asphaltene content could improve thehigh temperature performance of modified asphalt. Evidently, toproduce a polymer modified binder with good compatibility, thecontent of aromatics of the base asphalt should be sufficiently highfor the polymer to compete with asphaltenes. Therefore, it is rea-sonable to expect that the compatibility of SBS modified asphaltsmay be improved by the addition of aromatic oil [31]. However,an excessive content of aromatic or an insufficient content ofasphaltenes in base asphalt may lead to modified binders with asingle phase which show no significant improvement in mechani-cal properties. Otherwise, the viscosity of modified asphalt isincreasing with the range of the particle size distribution curvesnarrowing, which is in accord with the influence of the asphaltenecontent.
3.2. Influence of SBS structure on particle size distribution of SBS andthe properties of SBS modified asphalt
In order to investigate the effect of the structure of SBS includ-ing the types and block S/B ratios on the dispersion of SBS as wellas the performance of modified asphalt, four kinds of SBS with ra-dial, linear and different S/B ratios were selected. In this part, fourkinds of SBS including 1201, 1301, 1401, and 4303 were used asthe modifiers. QHD AH-70 asphalt was chosen as the base asphalt.The loading level of SBS was 3% by weight of modified asphalt. Themodification parameters have been mentioned in Section 2.2.
SBS is a tri-block copolymer with poly-styrene (PS) which is thethermoplastic end block and poly-butadiene (PB) which is the rub-bery midblock, linear and radial structure, different molecular
Fig. 3. Influence of asphalt types on the performance of SBS modified asphalt.
weights, and so on. And PS block and PB block play the differentrole in modification. As shown in Fig. 4, the S/B ratios have a signif-icant effect on the dispersion of SBS. On the contrary, radial andlinear SBS with the same S/B display almost present the same par-ticle size distribution curves. As the S/B ratio of linear SBS in-creases, the range of curves becomes narrower, and then wideragain. It is found that the range of the particle size distribution iswider than others when the S/B was 20/80, which is from 0 to6 lm, and the dispersion of SBS particles was heterogeneous.When the S/B ratio increases to 30/70, the SBS particles were bro-ken into small pieces and the range is from 0 to 2.0 lm. However,when the S/B ratio continues to increase, the range of the particlesize distribution is becoming wider again. Polystyrene (PS) blockstend to clump with each other and clumped PS blocks are held to-gether by poly-butadiene (PB) blocks, leading to a rubbery struc-ture. While, PS blocks from the hard segment impart strength tothe resin, PB blocks from the soft segment increase the elasticityof the copolymer [6,32]. Compared with the S/B ratio, the SBS typehas a different effect on the dispersion of SBS. There has a little dif-ference between the range of radial SBS and linear SBS. The molec-ular weights of radial SBS is twice times than that of linear SBS, andthe compatibility of radial SBS and asphalt is poorer, which havebad effect on SBS dispersion.
The solubility parameter is an important measurement to pre-dict compatibility between different materials, which has beenapplied in polymer and relative fields. The approximate solubilityparameters of the asphalt components and that of the blocks ofthe copolymers are listed in Table 3 [33]. It is found that asphalt-enes are the most polar components and the PB blocks are less po-lar than the PS ones. PB blocks are less polar than all the maltenesconstituents. Therefore, SBS is relatively miscible with maltenes,but almost completely immiscible with asphaltenes. The solubilityparameter of the blocks PB is 16.5–17.6, which are easily swollenby saturates. However, the solubility parameter of the blocks PSis 18.6–19.8, which have good compatibility with aromatics. So itcould be concluded that the asphalt components have a great effecton the dispersion of SBS. Generally speaking, with the blocks S/Bincreasing, the gathering energy of the blocks PS is more. There-fore, more energy is needed to disperse SBS in asphalt.
The relationships between the SBS structure and the perfor-mance of SBS modified asphalt are shown in Fig. 5. As the blockS/B ratio increases, the values of the performance of SBS modifiedasphalt including the softening point, the penetration at 25 �C, andthe viscosity at 135 �C have a peak value. This suggests that the SBS
Fig. 4. Influence of SBS structure on particle size distribution of SBS.
Table 3Solubility parameters of asphalt components and SBS polymer blocks.
Asphaltcomponent
Solubility parameter(MPa)0.5
Polymerblocks
Solubility parameter(MPa)0.5
Saturates 17.4–20 PS 18.6–19.8Aromatics 19–22.5 PB 16.5–17.6Resins 21.9–26.6Asphaltenes 24.9–32.9
Fig. 5. Influence of SBS structure on the performance of SBS modified asphalt.
F. Dong et al. / Construction and Building Materials 62 (2014) 1–7 5
structure has a great effect on the compatibility of modified as-phalt and there is a moderate block S/B ratio for SBS. It has beenreported that the glassy PS domains of SBS increase the stiffnessof asphalt for high temperature, whereas the rubbery PB midblocksresist thermal cracking at low service temperatures [1]. In addition,the ductility at 5 �C decreases regularly with the increase of S/B ra-tio. The PS is the hard segment and with the S/B ratio increasing,the hardness of SBS is growing, and so the tenacity of SBS becomesbadly. Notably, whether the type of SBS is radial or linear, the soft-ening point and the viscosity at 135 �C are higher than others whilethe penetration at 25 �C is lower than others when the block S/Bratio is 30/70, which are consistent with the effects of SBS structureon the dispersion of SBS. Meanwhile, the softening point and theviscosity of radial SBS modified asphalt is higher than that of linearone, which is due to the higher molecular weights and stereo-hin-drance effect of radial SBS.
Fig. 6. Influence of SBS content on particle size distribution of SBS.
3.3. Influence of SBS contents on particle size distribution of SBS andthe properties of SBS modified asphalt
The minimum percentage of polymer needed to ensure theformation of a continuous phase depends, to a greater extent, onthe base asphalt rather than on the polymer [34]. Meanwhile,SBS contents have significantly effect on the dispersion of SBSand the performance of SBS modified asphalt.
As shown in Section 3.3, the effect of the compatibility on theperformance of modified asphalt depends on the chemical compo-sition of asphalt and SBS as well as the contents of SBS. A linear SBSwhich is commonly used recently was selected and the loading le-vel of SBS designed were 1%, 3%, and 5% because of the max contentof SBS about 4–5% in industrial application. It is depicted that theparticle size distribution curves show a clear change in the disper-sion of SBS in modified asphalt as SBS polymer content increases at
shear rate of 3000 rpm, shear time of 60 min, and shear tempera-ture of 175 �C in Fig. 6.
It is found that the SBS contents have the greatest effect on thedispersion of SBS in asphalt presented in Fig. 6. The particle sizedistribution curves shows great changes as the contents increase.The range of the curve at the SBS content of 1.0% is the narrowestthan others, which is 0–1.6 lm. Meanwhile, the SBS is disperseduniformly in asphalt and the particle size is small. At low polymercontent, the small polymer globules which are swollen by the baseasphalt compatible fractions are spread homogenously in a contin-uous asphalt phase. That is to say, there is enough maltenes in as-phalt to swell SBS and then make swollen SBS disperse into smallpieces uniformly. When the SBS content increases to 3.0%, thecurve have two peaks and the range of particle size distributionis wider than that at content of 1.0%. However, when the contentof SBS continues to increase, particle size distribution curves ofSBS start to become complicated. Especially, when the content in-creases to 5%, the range of the curve becomes wider than others,which is 0–6 lm. At higher polymer concentrations, a larger quan-tity of polar aromatics is subtracted from maltenes, and therefore,the colloidal structure of asphaltene micelles or micellar aggre-gates is no longer stabilized and tends to collapse. Meanwhile,the maltenes in asphalt are limited [35]. SBS are not swollen suffi-ciently as the content of SBS increases. Compared with the initialcomposition of asphalt cement, the swelling of SBS cause an in-crease in asphaltene content, and finally leads to a hard matrix.So there is an optimum polymer content for the modified asphaltwhich has good performance and superior dispersion of SBS.Mohammad et al. [36] found that the phase morphology of twointerlocked continuous phases was an ideal microstructure forpolymer modified road asphalt, and the optimum polymer contentwas determined based on the formation of the critical network be-tween asphalt and polymer.
On the contrary, at the different polymer content, the effect ofdispersion of SBS on the performance of modified asphalt is differ-ent. As the content of polymer increases, the softening point of themodified asphalt increases, while the penetration at 25 �C and theductility at 5 �C decreases shown in Figs. 7a and 7b. There is limitedincrease in viscosity and softening point at a concentration of 1%because the SBS only acts as a dispersed polymer. As the penetra-tion and softening point results, the viscosities also give an indica-tion of the stiffening effect of SBS modification. The viscosity valuesand modification indices related to modified asphalt prepared byhigh content SBS are higher than that prepared by low contentSBS. This may be due to that the higher content of SBS needs more
Fig. 7a. Influence of SBS content on the performance of SBS modified asphalt.
Fig. 7b. Influence of SBS content on the performance of SBS modified asphalt.
6 F. Dong et al. / Construction and Building Materials 62 (2014) 1–7
maltenes at the same process condition. However, the maltenes inasphalt are limited. It should be also mentioned that the perfor-mance of the modified asphalt is not only dependent on thepolymer dispersion but also on the polymer content. This meansthe high values of polymer dispersion does not always reflect thecontinuous polymer phase. These results are consistent with theeffects of polymer content on the dispersion of SBS.
4. Conclusions
In this study, SBS copolymer was blended with asphalt toinvestigate the effect of SBS modification on asphalt binder proper-ties. The asphalt type, SBS structure and contents have significantimpacts on the particle size distribution of SBS polymer and theperformance of SBS modified asphalt.
The contents of aromatics in asphalt play a significant role incompatibility between asphalt and polymer, and the highercontents of aromatics was, the better the performance of modifiedasphalt. Meanwhile, asphaltenes content must be proper. The higharomatics content and the low asphaltenes content could improvethe dispersion of SBS in asphalt. With the range of the particle sizedistribution curves narrowing, the viscosity of modified asphaltincreases.
As the S/B ratio increases, there is a moderate S/B ratio for thedispersion of SBS and the performance of modified asphalt. Whenthe S/B ratio is 30/70, the particle size distribution curve is narrow-est and the performance of modified asphalt is improved higher
than others. However, the dispersion of SBS and the trends of per-formance of modified asphalt prepared by radial and linear SBS atthe S/B of 30/70 have little difference.
The content of SBS also has great effect on the dispersion of SBSand the performance of modified asphalt. However, the results arecontrary to that of the other factors. Lowering content of SBS isconducive to improve the dispersion of SBS, but has bad effect onthe performance of modified asphalt; in other words, the particlesize distribution becomes wider and the softening point of themodified asphalt increases, the penetration and the ductilitydecreases, as the content of SBS increases.
Acknowledgements
This work was supported by the National Natural Science Foun-dation of China (51008307), the Fundamental Research Funds forthe Central Universities (09CX04039A), and the Graduate innova-tion Project of China University of Petroleum (East China)(CX2013036).
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