Construction and Building Materials 35 (2012) 159–170

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Construction and Building Materials

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Performance of asphalt binder blended with non-modified and polymer-modifiednanoclay

Hui Yao a,b, Zhanping You b,⇑, Liang Li a, Xianming Shi c, Shu Wei Goh b, Julian Mills-Beale b, David Wingard d

a School of Civil Engineering and Architecture, Central South University, Changsha, Hunan 410075, Chinab Department of Civil and Environmental Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931-1295, USAc Department of Civil Engineering and Western Transportation Institute, Montana State University, Bozeman, MT 59717-4250, USAd Department of Civil Engineering, Clemson University, Clemson, SC 29634, USA

a r t i c l e i n f o a b s t r a c t

Article history:Received 2 September 2011Received in revised form 12 January 2012Accepted 25 February 2012

Keywords:AsphaltModified asphaltNon-modified nanoclayPolymer modified nanoclayNanomaterials modified asphalt

0950-0618/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.conbuildmat.2012.02.056

⇑ Corresponding author. Tel.: +1 906 487 1059; faxE-mail addresses: huiyao@mtu.edu (H. Yao), zyo

csu@126.com (L. Li), Xianming_s@coe.montana.edu (Goh), jnmillsb@mtu.edu (J. Mills-Beale), Wingar2@cle

This study investigated the rheological properties of asphalt binders modified with nanomaterial addi-tives. The additives used are non-modified nanoclay (NMN) and polymer modified nanoclay (PMN). Theywere added to the control PG 58-34 asphalt binder at concentrations of 2% and 4% by the weight of theasphalt binder, respectively. Superpave™ binder tests were employed to evaluate the characteristics ofthe nano-modified binders. Rheological properties of nano-modified asphalt were analyzed by use ofasphalt binder tests such as Rotational Viscosity (RV), Dynamic Shear Rheometer (DSR) and BendingBeam Rheometer (BBR). In addition, the short- and long-term aging properties of nano-modified asphaltwere analyzed, with the aging process simulated by Rolling Thin Film Oven (RTFO) and the PressureAging Vessel (PAV). The dissipated work per load cycle of all asphalt binders was examined, in orderto better understand the properties of nano-modified asphalt. The results reveal that both viscosityand complex shear modulus of asphalt binder remarkably increase when the NMN is added into the con-trol asphalt, and decrease slightly when the PMN is added. In addition, from the dissipated work perspec-tive, the overall performance of PMN modified asphalt binder is improved in terms of rutting and fatiguecracking resistance relative to the NMN modified asphalt binder.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Asphalt mixture is composed of asphalt, graded aggregates andair voids. Asphalt is a time–temperature viscoelastic material andits behaviors depend on both temperature and loading time. Thecomponents of asphalt are rather complex and they contain car-bon, hydrogen, nitrogen, sulfur, oxygen, etc. Researchers have beentrying to use different kinds of additives to modify the base asphaltin order to increase the resistance to pavement distress. In general,fibers and polymers are two main materials used in the asphaltmodification [1–5]. Fiber was one of the most widely used addi-tives to enhance the bonding between asphalt and aggregates orwithin asphalt since 4000 years old ago [6–12]. In addition, scien-tist and engineers tried to use the polymer Styrene Butadiene Sty-rene (SBS) to improve pavement fatigue and rutting resistance ofasphalt [13–16]. Performance of asphalt binder modified withSBS was investigated using different test methods. Properties suchas the asphalt composition, reaction between the modifier and as-

ll rights reserved.

: +1 906 487 1620.u@mtu.edu (Z. You), liliang_X. Shi), sgoh@mtu.edu (S.W.mson.edu (D. Wingard).

phalt or within asphalt, asphalt microstructure and rheology fea-tures, were evaluated by Fourier transform infrared (FTIR),atomic force microscopy (AFM) and Dynamic Shear Rheometer(DSR). Results show that SBS modified asphalt mixture can signif-icantly improve the asphalt binder performance under both highand low temperatures [14,15,17–20].

Recently, nanomaterials for asphalt mixture have beendeveloped rapidly as they have extensive and unique propertiessuch as the quantum effects, structural features, high surface work,spatial confinement and large fraction of surface atoms. Nanoma-terials possess an extraordinary potential for improving the perfor-mance of asphalt binders and mixtures. It is anticipated that thesemay enhance or modify the properties of asphalt pavement. Youet al. presented that nanoclay modified asphalt could increasethe shear complex modulus and reduced the strain failure rate ofbase asphalt. Furthermore, the addition of nanoclay woulddecrease the moisture damage of asphalt mixture [21,22].

In this study, two types of nanomaterials were used as additivesto modify the control asphalt PG 58-34: (1) non-modified nanoclay(NMN); and (2) polymer modified nanoclay (PMN), both obtainedfrom Nanocor Inc. (USA). The binder tests of Superpave™ wereconducted, including Rotational Viscosity (RV), Dynamic ShearRheometer (DSR), Bending Beam Rheometer (BBR), Rolling Thin

160 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

Film Oven (RTFO) and Pressure Aging Vessel (PAV), and the perfor-mance of nanomaterials modified asphalt (NMA) was investigated.Based on the results of these tests, it can be concluded that theaddition of NMN and increases the complex shear modulus (|G�|)of asphalt significantly, and improve the high-temperature perfor-mance of asphalt from the rutting and fatigue dissipated energyperspective. Compared with the NMN modified asphalt binderfrom the BBR test, the low-temperature properties of PMN modi-fied asphalt binder are slightly better.

2. Preparation and tests of nanomaterials modified asphalt

Nanoclay is widely used in the modification of polymer. It couldimprove the mechanical properties, heat resistance and biodegrad-ability of hybrid materials [21]. The raw nanoclay (NMN) is mont-morillonite; a 2-to-1 layered smectite clay mineral with a platestructure. The major sodium ions constitute the layer and thisstructure has high expansion pressure. It readily leads to exfolia-tion and dispersion of crystal in the form of micro-particles or layer[23]. NMN microstructure images are observed by Hitachi S-4700field emission scanning electron microscope (FE-SEM) (Fig. 1).Polymer modified nanoclay is used as a polymeric photosensitizer[24]. The PMN is normally produced from the hydrophilic nanoclaywith the organic cation exchange. Through the modification, thepermeability of composite material is reduced; tear and compres-sion strength is improved [25]. PMN FE-SEM microstructureimages are shown in Fig. 2. Obviously, the agglomeration phenom-ena happened in both NMN and PMN. In addition, in this study,two nanoclay materials (NMN is hydrophilic and PMN is hydro-phobic and organophilic via the modification by polysiloxane)were applied to modify the control asphalt. The PMN and NMN fea-ture a bulk density of is 0.251 g/cm3 and 0.678 g/cm3 respectivelyand both feature a maximum size of 200–400 nm in terms of as-pect ratio [26]. Asphalt graded PG 58-34 from a project site inGladstone Michigan was used as the control asphalt. It is notedthat the control asphalt was pre-modified with acrylonitrile buta-diene styrene (ABS) in order to improve the compatibility betweenthe asphalt and polymer, and meet the low temperature graderequirement.

Each nanomaterial, PMN or NMN were added to the base as-phalt at concentrations of 2% and 4% by the weight of control as-phalt, respectively. The modified asphalt binder was mixed withhigh shear mixing equipment at the condition of 4000 rpm rota-tional speed and of around 130 �C temperature. All samples weremixed for around 2 h prior to the Superpave™ binder tests. In addi-tion, microstructure images of 4% NMN and PMN modified asphaltbinder were also obtained by using a Hitachi SU6600 FE-SEM witha cryogenic stage and shown in Figs. 1 and 2. The SU6600 imagesshowed that the NMN was mainly found in conglomerates, whichranged in size from 50 to 15 lm. The dispersion of the PMN wasslightly better with an average conglomerate size of 4 lm, butthere were a few extremely large conglomerates (�80 lm). Fromthe figures, it can be seen that agglomeration phenomena ofnanomaterials also occured in the asphalt binder and nanomateri-als were melted uniformly in the control asphalt binder. It is pos-sible that chemical reaction was undertaken between thenanomaterials and control asphalt binder.

3. Results and discussion: rotational viscosity test

The rotational viscosity is the measurement of a fluid’s resistantto flow. Asphalt samples were measured with the Brookfield vis-cometer at 100 �C, 125 �C, 135 �C, 150 �C, 175 �C, and 190 �C. The27# spindle was selected and test temperatures covered the range

of mixing and compaction temperatures (AASHTO, 2006). The testresults are shown in Fig. 3.

Fig. 3 shows that with the addition of NMN in the control as-phalt binder, the viscosity of the modified asphalt increases byan average of 250% within 100 �C to 190 �C temperature range.However, the addition of PMN in the base asphalt does not resultin significant improvement in viscosity values and maintain thesame level with the control asphalt. Fig. 1 illustrates that all viscos-ity data under 135 �C pass the specification of Superpave™ Stan-dard, and are lower than the limit of 3 Pa s. The asphalt viscositydetermines the pumpability, mixability and workability of asphaltbinder. The high viscosity leads to the high mixing and compactiontemperature. It will cost more heating work for asphalt pavementconstruction. In light of the viscosity, the PMN modified asphaltbinder has more advantage relative to the NMN modified asphaltbinder. In addition, non-modified nanoclay was melted into the as-phalt binder and increases the viscosity for the mechanical, ther-mal, and barrier properties. Polymer modified nanoclay has theexcellent temperature resistance due to the polysiloxanes modifi-cation. That is the reason for lower viscosity.

4. Results and discussion: Complex shear modulus (|G�|) test

Dynamic Shear Rheometer (DSR) is used to characterize the vis-cous and elastic behavior of asphalt binder at the medium and hightemperatures. It measures the complex shear modulus (|G�|) andphase angle (d) of asphalt binder. The |G�| is used to evaluate therutting potential of asphalt binder at unaged or short-term agingcondition and the phase angle represents the time lag betweenthe applied shear stress and the resulting shear strain. When thephase angle is zero, the subject asphalt binder is a purely elasticmaterial, and when the phase angle is 90�, it is a purely viscousmaterial. High |G�| means stiffer in the asphalt binder at high tem-perature. It has potential to resist the deformation of asphalt pave-ment. Simultaneously, for rutting dissipated work per load cycle,the calculation equation is shown in the following equation:

Rutting : Wc ¼ pr20

1G�= sin d

� �ðstress-controlledÞ ð1Þ

And for fatigue cracking dissipated work per load cycle, the cal-culated equation is shown in the following equation:

Fatigue cracking : Wc ¼ pr20ðG

� sin dÞ ðstrain-controlledÞ ð2Þ

where Wc = work dissipated per load cycle, r = stress applied dur-ing load cycle, e = strain during load cycle, G� = complex shear mod-ulus, d = phase angle.

Permanent deformation resistance is conducted on the unagedand RTFO-aged asphalt binder and the fatigue cracking is con-ducted on the PAV-aged asphalt binder. In addition, with each cy-cle, when the load is applied, the work from each load istransferred into the pavement. A portion of the work is absorbedby the pavement and reflected as elastic rebound. The remainingwork is converted into damage in the form of rutting, fatigue crack-ing and crack propagation. Therefore, the low dissipated energiesper load cycle indicate that an asphalt binder has good resistanceability to rutting and fatigue cracking.

4.1. NMN modified asphalt binder

From Fig. 4, the complex shear modulus master curves of NMNmodified asphalt binder and control asphalt binder are displayed. Itcan be described that the complex modulus (|G�|) values of 2% and4% NMN modified asphalt binder are more than the control asphaltbinder, and the complex shear modulus (|G�|) values of 2% NMNmodified asphalt binder are close to that of control asphalt binder

(a) 20,000x magnification image of NMN

(b) 3,000x magnification image of NMN

(c) 1,500x magnification image of NMN

(d) 1,500x magnification image of 4% NMN modified asphalt binder

(e) 500x magnification imageof 4% NMNmodified asphalt binder

(f) 150x magnification image of 4% NMNmodified asphalt binder

Fig. 1. FE-SEM microstructure images of non-modified nanoclay and NMN modified asphalt binder.

H. Yao et al. / Construction and Building Materials 35 (2012) 159–170 161

at low temperatures. With the addition of 4% NMN in the controlasphalt binder, the complex shear modulus increases by an averageof 170% while the 2% NMN modified asphalt just increases by anaverage of 45%. Based on the literature reviews [23,25], when itis added into the control asphalt binder, it is likely that the ionsand layer of NMN is intercalated and exfoliated in the asphalt

binder due to the cation exchanges. Ca2+, Mg2+ and ammoniumin asphalt binder are the major exchangeable cations in the reac-tion process. The layer separations in the NMN result in higher sur-face work and it makes the intensive interaction with the asphaltbinder (Fig. 5). After the reactions, the more dense solid materialsare melted and stable bonding framework is formed. Therefore,

(a) 20,000x magnification image of PMN

(b) 3,000x magnification image of PMN

(c) 1500x magnification image of PMN

(d) 1,000x magnification image of 4% PMN modified asphalt binder

(e) 450x magnification image of 4% PMN modified asphalt binder

(f) 100x magnification image of 4% PMN modified asphalt binder

Fig. 2. FE-SEM microstructure images of polymer modified nanoclay and PMN modified asphalt binder.

162 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

asphalt binder microstructure causes the improvement of complexshear modulus and NMN modified asphalt binder has the potentialresistance to rutting. Furthermore, the work dissipated per load cy-cle is calculated for rutting influence, and results are shown inFig. 6.

Fig. 6 demonstrates that the amounts of work dissipated perloading cycle of control asphalt binder are lower than those of 2%

and 4% NMN modified asphalt binder, and the work dissipatedper loading cycle of 2% NMN modified asphalt binder is lower thanthat of 4% NMN modified asphalt binder. Additionally, with theaddition of 4% NMN in the control asphalt binder, the dissipatedwork per load cycle increases by an average of 40% while 2%NMN modified asphalt binder increases by an average of 10%relative to the control asphalt binder. However, from Fig. 2, the

5.0E+01

5.0E+02

5.0E+03

5.0E+04

100 125 135 150 175 190

Vis

cosi

ty v

alue

s (c

P)

Temperature (oC)

2% NMN 4% NMN

2% PMN 4% PMN

Control

Fig. 3. Viscosity values of control and nanomaterials modified asphalt binders (with standard error bars).

Fig. 4. Complex shear modulus (|G�|) master curves of control and NMN modified asphalt binders (with standard error bars).

Fig. 5. Schematic illustration of non-modified nanoclay microstructure changing in asphalt binder.

H. Yao et al. / Construction and Building Materials 35 (2012) 159–170 163

complex shear modulus of NMN modified asphalt is increased rel-ative to the control asphalt. That means that the addition of NMNin the control asphalt improves the resistance to rutting, but fromthe dissipated work perspective, the addition of NMN in the con-trol asphalt binder slows down the recovery ability of modified as-phalt binder. Therefore, NMN modified asphalt binder may havebetter performance of resistance to rutting relative to the controlasphalt binder.

4.2. PMN modified asphalt binder

From Fig. 7, the complex shear modulus master curves of PMNmodified asphalt binders are represented. Complex modulus (|G�|)

values of control asphalt binder are higher than those of 4% PMNmodified asphalt binder, and almost the same as 2% PMN modifiedasphalt binder. With the addition of 4% PMN in the control asphaltbinder, the complex shear modulus of the modified asphalt de-creases by an average of 33% while average modulus values of 2%PMN modified asphalt binder decreases by an average of 6%. Inaddition, the polymer modified nanoclay can disperse readily inpolymers, and has excellent temperature resistance and good resis-tance to certain acids and solvents. Compared with the NMN mate-rial, PMN is changed from a hydrophilic to a hydrophobic disk.Based on the literature reviews [23,25], due to the mechanicalshear force and thermodynamic driving force, the PMN layerstructure is easy to be exfoliated in the asphalt binder and the

Fig. 6. Work dissipated per load cycle of control and NMN modified asphalt binders under different temperatures (rutting influence, with standard error bars).

Fig. 7. Complex shear modulus (|G�|) master curves of control and PMN modified asphalt binders (with standard error bars).

164 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

compatibility of polymer improves. From the layer exfoliation, it islikely that the surface work increases and the ions and cation ex-changes in the asphalt binder become intensive (Fig. 8). The PMNproperty changes the microstructure of asphalt binder throughthe chemical reactions, and causes lower complex shear modulusand reduction of water permeability. Therefore, the amounts ofdissipated work per loading cycle of PMN modified asphalt binderand control asphalt binder are displayed in Fig. 9.

Fig. 9 illustrates that the 4% PMN modified asphalt binder hasthe lowest dissipated work per loading cycle of rutting, while thecontrol asphalt binder has the highest dissipated work per loadingcycle. In addition, the work of 4% PMN modified asphalt binder de-creases by an average of 35% while 2% PMN modified asphalt bin-der decreases by an average of 18%. The PMN modified asphaltbinder has lower dissipated work per loading cycle relative tothe NMN modified asphalt binder. Because of the polymer modifi-cation in the nanoclay, PMN has more potential to form bettermicrostructure of asphalt binder through the chemical reactions.From the dissipated work standpoints, the performance of resis-tance to rutting in the PMN modified asphalt binder improves aswell as the recovery ability of asphalt binder. Therefore, it can beconcluded that overall performance of PMN modified asphalt bin-der is better than the control asphalt binder, and 4% PMN modifiedasphalt binder improves most on the asphalt performanceincluding resistance to rutting.

4.3. NMN modified asphalt binder after RTFO Aging

From Fig. 10, the complex shear modulus master curves of NMNmodified asphalt binder after RTFO aging are revealed. The figureshows the complex shear modulus of 4% NMN modified asphaltbinder is higher than those of 2% NMN modified asphalt binderand control asphalt binder under the different temperatures. Inaddition, with the addition of 4% PMN in the control asphalt, thecomplex shear modulus (|G�|) increases by an average of 15% whilethe average values of 2% PMN modified asphalt binder increases byan average of 7%. The non-modified nanoclay was dispersed well inthe control asphalt and the stable network was formed after RTFOaging. The strength of modified asphalt was increased. Simulta-neously, the work dissipated per load cycle of rutting is performedand is shown in Fig. 9.

Fig. 11 shows that the work dissipated per load cycle of ruttinginfluence of the control asphalt binder is lower than those of 2%and 4% NMN modified asphalt binder under different tempera-tures after RTFO aging. Additionally, with the addition of 4%NMN in the control asphalt binder, the dissipated work increasesby an average of 50% while 2% NMN modified asphalt binder in-creases by an average of 12%. Therefore, the addition of NMN inthe control asphalt binder, the binder performance of resistanceto rutting does not improve significantly after the RTFO agingprocess.

Fig. 8. Schematic illustration of polymer modified nanoclay microstructure changing in asphalt binder.

Fig. 9. Work dissipated per load cycle of control and PMN modified asphalt binders under different temperatures (rutting influence, with standard error bars).

Fig. 10. Complex shear modulus (|G�|) master curves of control and NMN modified asphalt binders after RTFO aging process (with standard error bars).

H. Yao et al. / Construction and Building Materials 35 (2012) 159–170 165

4.4. PMN modified asphalt binder after RTFO aging

Fig. 12 displays the complex shear modulus master curves ofPMN modified asphalt binders after RTFO aging. The figure showsthat the complex shear modulus of the 4% PMN modified asphaltbinder is lower than the 2% PMN modified asphalt binder and con-trol asphalt binder under the different temperatures. The averagevalues of the 2% PMN modified asphalt binder is almost the sameas the control asphalt binder. With the addition of the 4% PMN in

the base asphalt binder, the complex shear modulus decreases byan average of 13% while the 2% PMN modified asphalt binder de-creases by an average of 8%. After RTFO aging, due to its polymermodification and compatibility, the polymer modified nanoclaywas sufficiently melted into the asphalt binder. The properties(high-heat resistance and chemical lining application) of PMNwere shown and the new stable framework in modified asphaltbinder was formed. This microstructure of modified asphalt binderdetermines that complex shear modulus of modified asphalt does

Fig. 11. Work dissipated per load cycle of control and NMN modified asphalt binders after RTFO aging (rutting influence, with standard error bars).

Fig. 12. Complex shear modulus (|G�|) master curves of control and PMN modified asphalt binders after RTFO aging process (with standard error bars).

166 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

not change much after the modification and holds the potential ofpavement performance improvement. Furthermore, the dissipatedwork per load cycle of rutting is calculated and shown in Fig. 13.

Fig. 13 shows that the control asphalt binder and 2% PMN mod-ified asphalt binder almost have the same dissipated work perloading cycle after RTFO aging, and the 4% PMN modified asphaltbinder has the lowest dissipated work of rutting influence. Withthe addition of 4% PMN in the control asphalt, the dissipated en-ergy decreases by an average of 9% while the 2% PMN modified as-phalt binder decreases by an average of 6%. Therefore, the additionof the 4% PMN in the control asphalt binder enhances the ruttingresistance performance of asphalt pavement.

4.5. NMN modified asphalt binder after PAV Aging

From Fig. 14, it is clear that with the addition of the NMN in thecontrol asphalt the complex shear modulus improves after the PAVaging. The complex shear modulus of NMN modified asphalt bin-der increases by an average of 10% at 13 �C while the complexshear modulus increases by an average of 5% at 39.2 �C. From thefatigue work standpoint, in Fig. 15, the control asphalt has the low-est dissipated work, and that means the performance of resistanceto the fatigue cracking in the modified asphalt binder may be de-creased slightly after PAV aging process. Therefore, the addition

of NMN may weaken the bonding interactions of molecules inthe modified asphalt.

4.6. PMN modified asphalt binder after PAV Aging

From Fig. 16, it can be seen that the PMN modified asphalt bin-der has higher complex shear modulus than the control asphalt’s at13 �C after PAV aging. However, at 39.2 �C, the complex shear mod-ulus of PMN modified asphalt binder decreases slightly. In Fig. 17,it is found the dissipated work per loading cycle of the control as-phalt binder is the highest at 39.2 �C. At 13 �C, PMN modified as-phalt binder almost has the same dissipated work as the controlasphalt binder. The PMN modified asphalt binder can improvethe resistance to the fatigue cracking of asphalt pavement. In addi-tion, PMN addition can delay the aging effect of the modified as-phalt binder and strengthen the interactions between moleculesin the asphalt binder. Therefore, the overall performance of PMNmodified asphalt binder is enhanced relative to the control asphalt.

5. Results and discussions: bending beam rheometer test

According to the Superpave™ specification, the low-tempera-ture performance of asphalt binder is evaluated by the bendingbeam rheometer test. The test evaluates the binder’s possible

Fig. 13. Work dissipated per load cycle of control and PMN modified asphalt binders after RTFO aging (rutting influence, with standard error bars).

Fig. 14. Complex shear modulus (|G�|) of control and NMN modified asphalt binder after PAV aging (with standard error bars).

Fig. 15. Work dissipated per load cycle of control and NMN modified asphalt binder after PAV aging (fatigue cracking influence, with standard error bars).

H. Yao et al. / Construction and Building Materials 35 (2012) 159–170 167

abilities of stress relaxation and thermal cracking in asphalt bend-ing beam samples. From the standard test, the deflection curves

can be drawn [27–29]. Then, Eq. (3) is used to calculate the stiff-ness of asphalt binder. In this research, the test temperature is

Fig. 16. Complex shear modulus (|G�|) of control and PMN modified asphalt binders after PAV aging (with standard error bars).

Fig. 17. Work dissipated per load cycle of control and PMN modified asphalt binders after PAV aging (fatigue cracking influence, with standard error bars).

Table 1m-Values of control and nano-modified asphalt binders at 60 s.

Asphalt binder type Time (s) Deflection (mm) Measured stiffness (MPa) m-Value Remarks

Control asphalt binder 60.0 0.445 178 0.317 Pass the specification2% NMN modified asphalt binder 60.0 0.414 189 0.309 Pass the specification4% NMN modified asphalt binder 60.0 0.404 196 0.304 Pass the specification2% PMN modified asphalt binder 60.0 0.436 182 0.339 Pass the specification4% PMN modified asphalt binder 60.0 0.425 187 0.315 Pass the specification

Fig. 18. Creep stiffness of control and nano-modified asphalt binders in the BBR test.

168 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

H. Yao et al. / Construction and Building Materials 35 (2012) 159–170 169

�24 �C and its stiffnesses and m-values are shown in Fig 16 andTable 1.

SðtÞ ¼ PL�

4bh�dðtÞð3Þ

where P = applied constant load (100 g or 0.98 N), L = distance be-tween beam supports (102 mm), b = beam width (12.5 mm),h = beam thickness (6.25 mm), S(t) = asphalt binder stiffness at aspecific time, d(t) = deflection at a specific time.

Fig. 18 shows that the control asphalt binder has higher deflec-tions and lower stiffnesses than the other asphalt binders duringthe loading time, and PMN modified asphalt binder has lower stiff-nesses than the NMN modified asphalt binder for the polymermodification in the nanoclay. It means that the control asphalt bin-der has better relaxation ability of stress and low temperature per-formance, as well as PMN modified asphalt binder is better thanNMN modified asphalt binder. However, it is noticed that thedeflection and stiffness of the NMN and PMN modified asphaltbinders are close to these of the control asphalt. In addition,according to the Superpave™ specification, all values at the 60 sloading time are lower than 300 MPa, and m-values at 60 s loadingtime are higher than 0.300 from Table 1. The low temperaturegrades of the NMN and PMN modified asphalt binders are the sameas the control asphalt binder. Therefore, the low temperature per-formance and stress relaxation ability of the NMN and PMN mod-ified asphalt binders are the same as the control asphalt.

6. Conclusions

Based on the tests results of nanomaterials modified asphalt,the following conclusions can be made:

1. The addition of NMN into the control asphalt binder increasesthe viscosity of the asphalt binder; however, the viscosity ofPMN modified asphalt binder slightly decreases relative to thecontrol asphalt binder. In addition, all asphalt viscosity data at135 �C pass the specification of Superpave™ Standard and itmeans the construction paving temperature does notinfluenced.

2. The NMN modified asphalt binder has higher complex shearmodulus than the control asphalt binder and the PMN modifiedasphalt binder has lower complex shear modulus than the con-trol asphalt binder before or after the RTFO and PAV aging pro-cess. From the dissipated work standpoints, the addition ofPMN in the control asphalt binder can improve the high tem-perature properties of unaged, RTFO-aged and PAV-agedasphalt binders. The addition of NMN in the control asphalt bin-der does not significantly enhance the high temperature prop-erties of unaged, RTFO-aged and PAV-aged asphalt binders. Inaddition, with the addition of PMN in the control asphalt binderincreases the recovery ability of asphalt binder while the addi-tion NMN in the control asphalt binder decreases the recoveryability of asphalt binder.

3. BBR test results show that the stiffnesses of NMN and PMNmodified asphalt binders approach to that of control asphaltbinder. From the Superpave™ grade perspective, the stressrelaxation and low temperature performance of NMN andPMN modified asphalt binders is the same as the controlasphalt.

In summary, the addition of polymer modified nanoclay (PMN)in the control asphalt binder enhances the performance of the as-phalt binder due to the polymer modification in nanoclay. Further-more, the research team plans to conduct the performance tests ofasphalt mixture. The ongoing research focuses on the microstruc-

ture performance and simulation model of asphalt binder and as-phalt mixture.

Acknowledgments

The authors would like to thank Su Ting Lau for her help in pre-paring and testing part of the laboratory work in this researchstudy. The experimental work was completed in the Transporta-tion Materials Research Center at Michigan Technological Univer-sity. The authors appreciate the funding support from CentralSouth University, under Project No. 2010ybfz048. Any opinions,findings, and conclusions or recommendations expressed in thismaterial are those of the authors and do not necessarily reflectthe reviews of any organizations.

References

[1] Liu X, Wu S. Study on the graphite and carbon fiber modified asphalt concrete.Constr Build Mater 2011;25(4):1807–11.

[2] Kaloush KE, Biligiri KP, Zeiada WA, Rodezno MC, Reed JX. Evaluation of fiber-reinforced asphalt mixtures using advanced material characterization tests. JTest Eval (JTE) 2010;38(4).

[3] Ye Q, Wu S, Li N. Investigation of the dynamic and fatigue properties of fiber-modified asphalt mixtures. Int J Fatigue 2009;31(10):1598–602.

[4] Anurag K, Xiao F, Amirkhanian SN. Laboratory investigation of indirect tensilestrength using roofing polyester waste fibers in hot mix asphalt. Constr BuildMater 2009;23(5):2035–40.

[5] Liu D, Luo Q, Wang H, Chen J. Direct synthesis of micro-coiled carbon fibers ongraphite substrate using co-electrodeposition of nickel and sulfur as catalysts.Mater Des 2009;30(3):649–52.

[6] Putman BJ, Amirkhanian SN. Utilization of waste fibers in stone matrix asphaltmixtures. Resour Conserv Recycl 2004;42(3):265–74.

[7] Nelson PK, Li VC, Kamada T. Fracture toughness of microfiber reinforcedcement composites. J Mater Civ Eng 2002;14(5):384–91.

[8] Pantazopoulou SJ, Zanganeh M. Triaxial tests of fiber-reinforced concrete. JMater Civ Eng 2001;13(5):340–8.

[9] Cleven MA. Investigation of the properties of carbon fiber modified asphaltmixtures. Thesis, Master of Science in Civil Engineering, MichiganTechnological University; 2000. p. 1–92.

[10] Cleven MA, Apul AT, Van Dam TJ. Demonstrating the functionality of carbonfiber modified asphalt mixtures. Final report prepared for Conoco, Inc, Civiland Environmental Engineering, Michigan Technological University; 1999.

[11] Pierre P, Pleau R, Rheaume M, Pigeon M. Influence of micro-fibres on thedrying behaviour of cement pastes and mortars. Sherbrooke, Can: CanadianSoc for Civil Engineering; 1997. p. 123–31.

[12] Pigeon M, Pleau R, Azzabi M, Banthia N. Durability of microfiber-reinforcedmortars. Cem Concr Res 1996;26(4):601–9.

[13] Ahmedzade P, Tigdemir M, Kalyoncuoglu SF. Laboratory investigation of theproperties of asphalt concrete mixtures modified with TOP–SBS. Constr BuildMater 2007;21(3):626–33.

[14] Al-Hadidy AI, Tan Y-q. The effect of SBS on asphalt and SMA mixtureproperties. J Mater Civil Eng 2011;23:504.

[15] Liu D-L, Yao H-B, Bao S-Y. Performance of nano-calcium carbonate and SBScompound modified asphalt. Zhongnan Daxue Xuebao (Ziran Kexue Ban). JCent South Univ (Sci Technol) 2007;38(3):579–82.

[16] Yildirim Y. Polymer modified asphalt binders. Constr Build Mater2007;21(1):66–72.

[17] Kalyoncuoglu SF, Tigdemir M. A model for dynamic creep evaluation of SBSmodified HMA mixtures. J Constr Build Mater 2010;25(2):859–66.

[18] Khodaii A, Mehrara A. Evaluation of permanent deformation of unmodifiedand SBS modified asphalt mixtures using dynamic creep test. Constr BuildMater 2009;23(7):2586–92.

[19] Awanti SS, Amarnath MS, Veeraragavan A. Laboratory evaluation of SBSmodified bituminous paving mix. J Mater Civil Eng 2008;20(4):327–30.

[20] Liu D-L, Bao S-Y. Research of improvement of SBS modified asphalt pavementperformance by organic monotmorillonite. J Build Mater 2007;10(4):500–4.China.

[21] You Z, Mills-Beale J, Foley JM, Roy S, Odegard GM, Dai Q, et al. Nanoclay-modified asphalt materials: preparation and characterization. Constr BuildMater 2011;25(2):1072–8.

[22] Goh SW, Akin M, You Z, Shi X. Effect of deicing solutions on the tensile strengthof micro- or nano-modified asphalt mixture. Constr Build Mater2011;25(1):195–200.

[23] Jahromi SG, Khodaii A. Effects of nanoclay on rheological properties of bitumenbinder. Constr Build Mater 2009;23(8):2894–904.

[24] Drozd D, Szczubialka K, Nowakowska M. Novel hybrid photosensitizers:photoactive polymer-nanoclay. J Photochem Photobiol A 2011;215(2–3):223–8.

[25] Simon M, Stafford K, Ou D. Nanoclay reinforcement of liquid silicone rubber. JInorg Organomet Polym Mater 2008;18(3):364–73.

170 H. Yao et al. / Construction and Building Materials 35 (2012) 159–170

[26] He X, Shi X. Chloride permeability and microstructure of portland cementmortars incorporating nanomaterials. Trans Res Rec: J Transport Res Board2008;2070(-1):13–21.

[27] Liu S, Cao W, Shang S, Qi H, Fang J. Analysis and application of relationshipsbetween low-temperature rheological performance parameters of asphaltbinders. Constr Build Mater 2010;24(4):471–8.

[28] Liu S, Ma C, Cao W, Fang J. Influence of aluminate coupling agent on low-temperature rheological performance of asphalt mastic. Constr Build Mater2009;24(5):650–9.

[29] Lu X, Redelius P. Effect of bitumen wax on asphalt mixture performance.Constr Build Mater 2007;21(11):1961–70.