Research ArticleMultiscale Study on the Modification Mechanism of Red MudModified Asphalt

Tao Fu1 JianHui Wei 1 Huiming Bao 2 and Junlin Liang 1

1College of Civil Engineering and Architecture Guangxi University Nanning 530004 China2College of Civil Engineering and Architecture Guilin University of Technology Guilin 541004 China

Correspondence should be addressed to Huiming Bao bhming163com and Junlin Liang ljl_1217126com

Received 6 May 2020 Revised 19 June 2020 Accepted 8 July 2020 Published 13 August 2020

Academic Editor Yuqing Zhang

Copyright copy 2020 Tao Fu et al 1is is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Red mud a waste residue of aluminium industry was used as modified asphalt material to prepare red mud modified asphalt andred mud modified asphalt under freeze-thaw cycles 1e matrix asphalt (MA) red mud modified asphalt (RMMA) and red mudmodified asphalt under freeze-thaw cycles (RMMAFC) were studied by scanning electron microscopy (SEM) Fourier transforminfrared spectrometry (FTIR) atomic force microscopy (AFM) and differential scanning calorimetry (DSC) Microscopicexperiments were conducted to investigate the modification performance and mechanism 1e modification mechanism of redmud modified asphalt was investigated using molecular dynamics simulation in this study 1e results show that red mud canform a uniform and stable blending system with base asphalt after adding base asphalt 1e structure of asphalt after adding redmud and adding redmud and freezing-thawing cycles does not change1e bee-structure decreases obviously with the addition ofred mud by atomic force microscopy (AFM) Density decreases gradually but bee-structure height increases obviously bee-structure of red mudmodified asphalt is destroyed after freeze-thaw cycles1rough differential scanning calorimetry (DSC) afteradding red mud heat absorption decreases Freeze-thaw cycles greatly reduce heat absorption of red mud modified asphaltConstructing molecular model of major components of red mud (Fe2O3 Al2O3) and asphaltene simulation results show that theinterfacial energy between asphaltene and red mudrsquos main components Fe2O3 and Al2O3 at minus10degC 25degC and 170degC is strongerthan that of Fe2O3 1e results of calculating the interfacial energy of asphaltene on the chemical composition surface of red mudare negative It can be seen that there are adsorption effects on the surface of asphaltene and red mud 1erefore increasing thecontent of Al2O3 or decreasing the content of Fe2O3 in red mud is beneficial to the adsorption of asphaltene

1 Introduction

By the end of 2019 Chinarsquos expressway has reached 485million kilometers ranking the first in the world Asphaltpavement has gradually become the first choice of high-grade highway pavement in China due to its goodsmoothness comfortable driving and beautiful visionHowever in recent years with the continuous increase oftraffic load rutting has gradually become one of the maindamage types of asphalt pavement in China and ruttingdamage of some roads is up to 30 [1] Rutting has beenlisted as an independent detection index in the evaluationstandard of highway technical condition which shows theimportance of rutting disease 1erefore in the process of

asphalt pavement design and construction preventing theoccurrence of rutting diseases is a key concern 1e ruttingdisease is directly related to the high temperature perfor-mance of asphalt and mixtures It has always been a hot spotof pavement material research to use different modifiers toimprove the high temperature performance of asphalt andimprove the rutting resistance of pavement [2ndash4] In view ofthe shortcomings of asphalt performance researchers invarious countries have studied the modification of asphalt byadding modifiers [5]

Red mud is the industrial waste produced when aluminais extracted from aluminium industry With the vigorousdevelopment of aluminium industry the discharge of redmud is increasing causing serious environmental disasters

HindawiAdvances in Materials Science and EngineeringVolume 2020 Article ID 2150215 9 pageshttpsdoiorg10115520202150215

So the utilization of red mud is imminent [6] Red mud hasbeen widely used in metal precipitation building materialsand environmental remediation [7ndash22] In recent yearsresearchers have found that inorganic material modifier notonly can improve the interface between asphalt and ag-gregate but also has the characteristics of simple productionprocess low price excellent performance and abundantreserves Many researchers have used red mud as fillers [23]Zhang and Sun et al recognize the efficiency of red mud asmineral filler three different filler materials includinglimestone hydrated lime and fly ash were selected andcompared It is indicated that the red mud increased thestiffness and elastic behavior of the corresponding asphaltmastic [24] Zhang and Li et al studied the influence of redmud on the properties of asphalt mortars and asphaltmixtures It is indicated that the performance of porousasphalt with redmud filler at 09 FB ratio exhibited enhancedperformance for raveling and rutting resistance [25] Inorder to study the interaction of red mud and asphaltfurther the microtests of matrix asphalt (MA) red mudmodified asphalt (RMMA) and red mud modified asphaltafter freeze-thaw cycles (RMMAFC) are carried out in-cluding scanning electron microscopy Fourier transforminfrared spectrometry (FTIR) and atomic force microscopyMolecular dynamics simulation is introduced to analyze redmud modification at multi-scale Asphalt and its modifi-cation mechanism were discussed

2 Material Properties

21 Experimental Design

211 Material AH-70 paving asphalt is obtained fromSinopec ldquoDonghairdquo Branch of Maoming GuangdongChina 1e corresponding technical indexes meet thetechnical requirements of road petroleum asphalt (JTG F40-2004) 1e basic properties of the asphalt are shown inTable 1

1e red mud used is the industrial waste residue formedduring the production of alumina by Bayer process in analumina plant in Guangxi It is a kind of highly alkaline (pHvalue is between 10 and 125) high content of Fe2O3 andAl2O3 and large compressibility cemented pore framestructure soil with a particle size of only 0088ndash025mm1ehydraulic components such as β-dicalcium silicate make ithave solidification ability

Snow-melting salt which is the commonly used NaCl inprojects is produced by Xilong Chemical Industry and itsperformance meets the requirements of GBT 23851-2009road deicing snow-melting agent

212 Preparation of Red Mud Modified Asphalt Red mudrawmaterials from the redmud yard are put into the oven anddried at 80degC for 24 hours 1e red mud is ground to pass the0075mm sieve by ball grinder 1e modified asphalts wereprepared using a high shear mixer Asphalt was heated until itbecomes a fluid at 170degC1en redmud compoundwas addedinto asphalt and the mixture was blended at 4000 rpm for30min (by testing the basic properties of red mud modified

asphalt before the optimum content of red mud is 11) 1efreeze-thaw samples were prepared according to AASHTO-283 Lottman test method 1e material was taken out and putinto a constant temperature environment at 25degC On the basisof the above preparation the following operations werecontinued (1) sampling was saturated with water for 4minutes in vacuum (2) sampling was frozen for 16 hours in arefrigerator at minus10degC and (3) sampling was taken out andbathed in an incubator at 60degC for 24 hours [24]

213 Test Method

(1) Differential Scanning Calorimetry A DSC spectrometer(Zetzseh DSC204) produced in Germany was used todetermine the functional characteristics of asphalt in theexperiment at a rate of 10degCmin a nitrogen flow rate of30mlmin a starting temperature of 10degC and an endingtemperature of 200degC

(2) Atomic Force Microscopy AFM (Bruker DimensionICON) was used to test MA RMMA and RMMAFC InAFM experiment a tiny (with a length of 125 μm naturalfrequency of 70 kHz and spring constant of 3Nm) andspiky tip is attached at the unsupported end of a cantileverand kept close to an asphalt film Due to close contact of thetips and the surface of the film impulsive or attractive forcebetween the atoms of top layer of asphalt and AFM is createdwhich makes the deflection of the cantilever 1e extent ofthe deflection absolutely depends on the developed forceinvolving the molecules of the tips and the film

(3) Scanning ElectronMicroscopy SU5000 Scanning ElectronMicroscope (SEM) produced by Hitachi High-TechnologiesCorporation of Japan was used to test asphalt samples 1easphalt samples were treated by hot melting cooled to roomtemperature and then tested by spraying gold

(4) Fourier Transform Infrared Spectroscopy 1e instrumentused in the experiment is Nicofe 7T40FTIR FourierTransform Infrared Spectrometer made in the United Stateswhich was used to determine the functional characteristics ofasphalt in wavenumbers ranging from 400 cmminus1 to4000 cmminus1

3 Results and Discussion

31 Fourier Transform Infrared Spectrometric (FTIR)Analysis 1e strength of the peak depends on the change ofdipole moment when the molecule vibrates 1e smaller thechange of dipole moment the weaker the band strength

Table 1 Technical properties of 70 matrix asphalt

Technical indicators Industry standard Test resultsPenetration (25degC) (01mm) 60ndash80 651Ductility (15degC) (cm) ge100 1045Softening point (degC) ge46 485Flash point (degC) ge260 299Solubility () ge995 9988

2 Advances in Materials Science and Engineering

Figure 1 shows that the absorption intensity of infraredspectrum peaks of base asphalt RMMA and RMMAFC aredifferent Table 2 shows the absorption position and vi-bration type of group within the range of 3700ndash3100 cmminus1 offunctional group location which was ascribed to the hy-droxyl (O-H) vibrations 1e absorption peak strength ofbase asphalt is greater than that of RMMA and RMMAFCwhich indicates that the O-H bond is reduced to a certainextent after adding modified asphalt to red mud and thevibration effect of O-H bond is weakened Freeze-thawcycles have little effect on O-H bonds in red mud asphalt1e change of absorption peak strength in the vicinity of1445 cmminus1 mainly indicates the existence of hydroxyl groupsin asphalt and the peak value of modified asphalt afterfreeze-thaw cycles decreases slightly 1e change of ab-sorption peak intensity in the vicinity of 1035 cmminus1 mainlyindicates the change of the vibration frequency of sulfoxideSO functional group In the range of 600 cmminus1 to 950 cmminus1it is also called benzene ring substitution zone the areawhere the aromatic components in asphalt are located 1esubstitution reaction occurs at different positions of benzenering in the aromatic components 1e change of absorptionpeak intensity indicates that substitution reaction may occuron benzene ring 1e absorption peak intensity of baseasphalt is stronger than that of freeze-thaw 1e absorptionpeak strength of RMMAFC is higher than that of RMMA1e absorption peak strength of RMMAFC is slightlyweakened indicating that the aromatic content of red mudmodified asphalt in freezing and thawing cycles is reduced1e functional groups of RMMA and RMMAFC werecombination of functional of groups of MA No new peaksappeared which indicated that the red mud added intoasphalt was mainly a physical adsorption and no chemicalreaction occurred

32 Scanning Electron Microscopic (SEM) Analysis1rough Figure 2 it can be seen from the scanning results ofelectron microscope that the surface of matrix asphalt is veryuniform and belongs to homogeneous structure For RMMA(Figure 3) the mixing of red mud powder and base asphaltstill belongs to two-phase structure Red mud powder isdistributed in asphalt in the form of flake Because theparticle size of red mud powder is small and the specificsurface area is large there is a large surface energy among thered mud particles At the same time red mud powder ab-sorbs part of the oil in asphalt to produce adsorption effectresulting in partial swelling and overlapping phenomenon1e addition of red mud powder changes the composition ofasphalt the oil content in asphalt is an important reason forthe fluidity of asphalt and the wax in asphalt will cause theasphalt to become soft at high temperature and brittle at lowtemperature Red mud absorbs part of the oil in the asphaltresulting in the relative decrease of free wax content in theasphalt thus the high temperature stability of the modifiedasphalt is increased the decrease of oil content in the asphaltmeans that the relative content of asphaltene and gum isincreased the asphaltene determines the viscosity and sta-bility sensitivity of the asphalt material and gum determines

the ductility of the asphalt material With the increase of therelative content of asphaltene and gum the temperaturesensitivity of modified asphalt is increased correspondinglyFor RMMAFC (Figure 4) a large number of salt grainsappear in the image and the volume is large which seriouslydamages the asphalt membrane 1e modulus of red mudparticles at low temperature is higher than that of asphaltmatrix which can produce high stress concentration andinduce a large number of craze and shear band 1e gen-eration and development of craze and shear band consume alot of energy so it can improve the modulus of low tem-perature corresponding to the glass transition temperatureand ensure the flexibility of asphalt at low temperature

RMMAFCRMMA

100959085807570656055

Abs

orba

nce (

A)

0 1000 2000 3000 4000

Wavenumber (cmndash1)

3322

1445

1035717

MA

Figure 1 FTIR spectra of asphalt samples

Table 2 Group absorption position and vibration type

Wavenumber(cmminus1)

Functionalgroup Vibration type

3322 O-H Stretching vibration

1445 C-C In-plane deformationvibration

1035 SO Oxidation reaction717 C-H Vibration absorption peak

SU5000 50kV 80mm times 200 SE(L) 200microm

Figure 2 MA by electron microscopy

Advances in Materials Science and Engineering 3

33 Atomic Force Microscopic (AFM) AnalysisFigures 5ndash7 show AFM plots of MA RMMA and RMMAFCat room temperature From the AFM diagram of asphalt itcan be seen that the bee-structure of base asphalt is dense1e bee-structure decreases obviously with the addition ofred mud and the density of bee-structure decreases grad-ually but the bee-structure height increases obviously 1ebee-structure of RMMAFC is destroyed and its distributionis not uniform 1e polarity of asphalt mainly comes fromheterocyclic atoms in asphalt the bee-structure is mainlyaffected by the polarity of asphalt 1e asphaltene micelles inasphalt are not completely dispersed in the medium and thecontinuous phase is less After adding red mud powder thebee-structure in asphalt presents a long and large form andthe continuous phase increases 1is is because after addingred mud powder to base asphalt the light components inasphalt combine with red mud to form macromoleculewhich results in the change of the relative content of asphaltcomponents thus affecting the temperature sensitivity ofasphalt Compared with the RMMA and RMMAFC the bee-structure in asphalt area and dense are decreased Afterfreeze-thaw cycle red mud particles diffuse in asphalt toform smaller aggregates 1e content of components con-tinues to change in which the light components are dis-persed from the original structure under freeze-thaw actionand fused with small aggregates to form a new aggregate Atthe same time due to the action of salt solution the lightcomponents of modified asphalt becomemore which resultsin the weakening of the direct connection effect between redmud powder and asphalt matrix resulting in asphalt 1etemperature sensitivity becomes more sensitive and the lowtemperature performance decreases

In order to quantitatively characterize the roughness ofbase asphalt RMMA and RMMAFC the image informationof asphalt by AFM was further analyzed and counted 1ehigh root mean square roughness arithmetic mean devia-tion roughness and peak coefficient were selected as thecharacteristic parameters to evaluate the surface of asphaltRelevant information of base asphalt RMMA andRMMAFC was extracted and analyzed 1e results areshown in Table 3 Generally speaking the surface roughness

of RMMA is higher than that of MA and that of RMMAFCFor the index of peak coefficient usually when the peakcoefficient is less than 3 there are many peaks and valleys inthe image surface morphology when the peak coefficient ismore than 3 it shows that the image surface morphology isflat and there are not too many peaks and valleys Com-bining with the morphology of AFM the bee-structuredecreases obviously with the addition of red mud and thedensity of bee-structure decreases gradually but the bee-structure height increases obviously 1is is due to theswelling effect of red mud added into asphalt which iscaused by the adsorption of free components in asphalt byred mud particles 1e bee-structure of RMMAFC isdestroyed and its distribution is not uniform 1e red mud-asphalt matrix structure is destroyed after freeze-thaw cyclesresulting in poor connection between red mud and asphaltwhich also leads to a decline in the performance of RMMA

34 Differential Scanning Calorimetric (DSC) Analysis Basedon Molecular Dynamics Simulation Taking base asphaltRMMA and RMMAFC as examples we can conclude fromTable 4 that the properties of RMMA and MA are roughlythe same while RMMAFC has obvious differences 1e totalendothermic peak energy of MA is 4308 Jg RMMA is3750 Jg and RMMAFC is 1281 Jg 1e smaller the en-dothermic peak energy is the more stable the properties ofasphalt are It can be seen from the degree and width of peakthat the heat absorption of asphalt is reduced and the peaktemperature is increased after red mud modification 1ethermal stability of asphalt is improved after red mudmodification and the rheological properties of asphalt arealso changed so that the temperature sensitivity of asphalt isreduced From the point of view of optimizing the perfor-mance of asphalt materials it is necessary to delay thethermal diffusion speed of asphalt molecules 1is requiresreducing the free volume of asphalt materials which can beachieved by adding inorganic materials or some macro-molecule materials so as to increase the ldquostiffnessrdquo of asphaltmaterials structure to a certain extent and to make asphaltmaterials 1e large voids in asphalt become smaller which

SU5000 50kV 83mm times 100k SE(L) 500nm

Figure 4 RMMAFC by electron microscopy

SU5000 50kV 77mm times 600 SE(L) 500microm

Figure 3 RMMA by electron microscopy

4 Advances in Materials Science and Engineering

200nm

ndash200nmHeight 40 microm

(a) (b)

Figure 5 AFM of MA

250 nm

ndash250 nmHeight 20 microm

(a) (b)

Figure 6 AFM of RMMA

250nm

ndash250nmHeight 40 microm

(a) (b)

Figure 7 AFM of RMMAFC

Advances in Materials Science and Engineering 5

restricts the synergistic movement of molecular chains inasphalt and achieves the purpose of reducing the thermalmotion range of asphalt molecules

35 Analysis of Red Mud-Asphalt Interface Energy Based onMolecular Dynamics Simulation In this paper the interfacemodel of asphaltene molecule on red mud surface wasconstructed by molecular simulation software (materialsstudio) 1e adsorption energy of red mud modified asphaltat mixing temperature and before and after freeze-thaw wasstudied by molecular dynamics simulation

1e models of asphaltene molecule (Figure 8) on twomain components of red mud Fe2O3 and Al2O3 wereestablished at minus10degC 25degC and 170degC (minus10degC is thetemperature in freeze-thaw cycles 25degC is the indoortemperature and 170degC is the heating temperature ofasphalt) 1rough the building tool in Materials Studiotoolbar the crystal plane of (0 0 1) is cut then severallayers of thickness are superimposed according to dif-ferent chemical composition and the crystal plane isoptimized by Geometry Optimization geometry structureoptimization tool in Forcite module At the same timeenergy is selected before the optimization of crystal planeis carried out 1e cell compass force field parameters aregiven by the necklace Under the NVT ensemble condi-tion the optimized interface model performs 200 PSdynamic calculation Given the initial position as arandom distribution the simulated temperatures areminus10degC 25degC and 170degC 1e Andersen temperaturecontrol method is used to control the temperature with atime step of 10 fs Finally a unit of Fe2O3 and anasphaltene with lattice parameters of a b 3021 A andc 431255 A was used As for the Al2O3 and anasphaltene a unit cell with dimension of a b 57108 Aand c 8660667 A was used 1e final bi-materials in-terface between asphaltene and two main components ofred mud (Fe2O3 and Al2O3) was built as shown inFigure 9

1erefore after the dynamic calculation of the in-terface model of asphaltene system on the chemicalcomposition surface of red mud the possible parametersof the interface can be obtained by the potential energy

calculation of each system of the interface model in turn[25 26] However in the process of dynamic simulationthe adsorption model with the lowest energy is neededfirst because the model with the lowest energy is usuallyconsidered as the optimal model of adsorption state andthe formula for calculating the interfacial interactionenergy is as follows

ΔE Einteraction Etotal minus Esurface + Easphalt1113872 1113873 (1)where Esurface is the total energy of the system when thelowest energy reaches the stable state after dynamics Easphaltis obtained by deleting the chemical composition of theunderlying aggregate and calculating the retained asphal-tene and ΔE represents the interaction energy betweenoxide interface and asphaltene interface

According to literature [26] the greater the negativevalue of the interaction energy ΔE between the chemicalcomposition of redmud and asphaltene in characterizing thestability of the adsorption system the greater the interactionbetween the chemical composition of red mud andasphaltene and the stronger the adsorption of asphaltene onthe surface of the chemical composition of red mud On thecontrary if ΔE is 0 or positive it indicates that asphaltenehas little or no adsorption on the surface of red mudchemical composition

From Table 5 the following can be concluded

(1) When asphaltene is in contact with the surface ofchemical composition of Fe2O3 and Al2O3 the re-sults of interfacial interaction energy are negativewhich indicates that there must be some adsorptionbetween asphaltene and the surface of chemicalcomposition of Fe2O3 and Al2O3

Table 3 Asphalt AFM image parameters analysis

Type R q (nm) R a (nm) KurtosisMA 210 171 257RMMA 486 249 242RMMAFC 150 094 149R q a root mean square roughness parameter Ra an arithmetic mean roughness kurtosis peak coefficient

Figure 8 Asphaltene molecular structure

Table 4 Test results of state transition process of asphalt

Asphalt Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Total heatabsorption (Jmiddotgminus1)

MA 1457 minus1515 minus2926sim51 2851 1912 51sim4367 4308RMMA 1119 minus1580 minus2906sim476 2631 1919 476sim4386 3750RMMAFC 0290 minus1999 minus2067simminus387 0991 2986 2237sim5421 1281

6 Advances in Materials Science and Engineering

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

Figure 1 shows that the absorption intensity of infraredspectrum peaks of base asphalt RMMA and RMMAFC aredifferent Table 2 shows the absorption position and vi-bration type of group within the range of 3700ndash3100 cmminus1 offunctional group location which was ascribed to the hy-droxyl (O-H) vibrations 1e absorption peak strength ofbase asphalt is greater than that of RMMA and RMMAFCwhich indicates that the O-H bond is reduced to a certainextent after adding modified asphalt to red mud and thevibration effect of O-H bond is weakened Freeze-thawcycles have little effect on O-H bonds in red mud asphalt1e change of absorption peak strength in the vicinity of1445 cmminus1 mainly indicates the existence of hydroxyl groupsin asphalt and the peak value of modified asphalt afterfreeze-thaw cycles decreases slightly 1e change of ab-sorption peak intensity in the vicinity of 1035 cmminus1 mainlyindicates the change of the vibration frequency of sulfoxideSO functional group In the range of 600 cmminus1 to 950 cmminus1it is also called benzene ring substitution zone the areawhere the aromatic components in asphalt are located 1esubstitution reaction occurs at different positions of benzenering in the aromatic components 1e change of absorptionpeak intensity indicates that substitution reaction may occuron benzene ring 1e absorption peak intensity of baseasphalt is stronger than that of freeze-thaw 1e absorptionpeak strength of RMMAFC is higher than that of RMMA1e absorption peak strength of RMMAFC is slightlyweakened indicating that the aromatic content of red mudmodified asphalt in freezing and thawing cycles is reduced1e functional groups of RMMA and RMMAFC werecombination of functional of groups of MA No new peaksappeared which indicated that the red mud added intoasphalt was mainly a physical adsorption and no chemicalreaction occurred

32 Scanning Electron Microscopic (SEM) Analysis1rough Figure 2 it can be seen from the scanning results ofelectron microscope that the surface of matrix asphalt is veryuniform and belongs to homogeneous structure For RMMA(Figure 3) the mixing of red mud powder and base asphaltstill belongs to two-phase structure Red mud powder isdistributed in asphalt in the form of flake Because theparticle size of red mud powder is small and the specificsurface area is large there is a large surface energy among thered mud particles At the same time red mud powder ab-sorbs part of the oil in asphalt to produce adsorption effectresulting in partial swelling and overlapping phenomenon1e addition of red mud powder changes the composition ofasphalt the oil content in asphalt is an important reason forthe fluidity of asphalt and the wax in asphalt will cause theasphalt to become soft at high temperature and brittle at lowtemperature Red mud absorbs part of the oil in the asphaltresulting in the relative decrease of free wax content in theasphalt thus the high temperature stability of the modifiedasphalt is increased the decrease of oil content in the asphaltmeans that the relative content of asphaltene and gum isincreased the asphaltene determines the viscosity and sta-bility sensitivity of the asphalt material and gum determines

the ductility of the asphalt material With the increase of therelative content of asphaltene and gum the temperaturesensitivity of modified asphalt is increased correspondinglyFor RMMAFC (Figure 4) a large number of salt grainsappear in the image and the volume is large which seriouslydamages the asphalt membrane 1e modulus of red mudparticles at low temperature is higher than that of asphaltmatrix which can produce high stress concentration andinduce a large number of craze and shear band 1e gen-eration and development of craze and shear band consume alot of energy so it can improve the modulus of low tem-perature corresponding to the glass transition temperatureand ensure the flexibility of asphalt at low temperature

RMMAFCRMMA

100959085807570656055

Abs

orba

nce (

A)

0 1000 2000 3000 4000

Wavenumber (cmndash1)

3322

1445

1035717

MA

Figure 1 FTIR spectra of asphalt samples

Table 2 Group absorption position and vibration type

Wavenumber(cmminus1)

Functionalgroup Vibration type

3322 O-H Stretching vibration

1445 C-C In-plane deformationvibration

1035 SO Oxidation reaction717 C-H Vibration absorption peak

SU5000 50kV 80mm times 200 SE(L) 200microm

Figure 2 MA by electron microscopy

Advances in Materials Science and Engineering 3

33 Atomic Force Microscopic (AFM) AnalysisFigures 5ndash7 show AFM plots of MA RMMA and RMMAFCat room temperature From the AFM diagram of asphalt itcan be seen that the bee-structure of base asphalt is dense1e bee-structure decreases obviously with the addition ofred mud and the density of bee-structure decreases grad-ually but the bee-structure height increases obviously 1ebee-structure of RMMAFC is destroyed and its distributionis not uniform 1e polarity of asphalt mainly comes fromheterocyclic atoms in asphalt the bee-structure is mainlyaffected by the polarity of asphalt 1e asphaltene micelles inasphalt are not completely dispersed in the medium and thecontinuous phase is less After adding red mud powder thebee-structure in asphalt presents a long and large form andthe continuous phase increases 1is is because after addingred mud powder to base asphalt the light components inasphalt combine with red mud to form macromoleculewhich results in the change of the relative content of asphaltcomponents thus affecting the temperature sensitivity ofasphalt Compared with the RMMA and RMMAFC the bee-structure in asphalt area and dense are decreased Afterfreeze-thaw cycle red mud particles diffuse in asphalt toform smaller aggregates 1e content of components con-tinues to change in which the light components are dis-persed from the original structure under freeze-thaw actionand fused with small aggregates to form a new aggregate Atthe same time due to the action of salt solution the lightcomponents of modified asphalt becomemore which resultsin the weakening of the direct connection effect between redmud powder and asphalt matrix resulting in asphalt 1etemperature sensitivity becomes more sensitive and the lowtemperature performance decreases

In order to quantitatively characterize the roughness ofbase asphalt RMMA and RMMAFC the image informationof asphalt by AFM was further analyzed and counted 1ehigh root mean square roughness arithmetic mean devia-tion roughness and peak coefficient were selected as thecharacteristic parameters to evaluate the surface of asphaltRelevant information of base asphalt RMMA andRMMAFC was extracted and analyzed 1e results areshown in Table 3 Generally speaking the surface roughness

of RMMA is higher than that of MA and that of RMMAFCFor the index of peak coefficient usually when the peakcoefficient is less than 3 there are many peaks and valleys inthe image surface morphology when the peak coefficient ismore than 3 it shows that the image surface morphology isflat and there are not too many peaks and valleys Com-bining with the morphology of AFM the bee-structuredecreases obviously with the addition of red mud and thedensity of bee-structure decreases gradually but the bee-structure height increases obviously 1is is due to theswelling effect of red mud added into asphalt which iscaused by the adsorption of free components in asphalt byred mud particles 1e bee-structure of RMMAFC isdestroyed and its distribution is not uniform 1e red mud-asphalt matrix structure is destroyed after freeze-thaw cyclesresulting in poor connection between red mud and asphaltwhich also leads to a decline in the performance of RMMA

34 Differential Scanning Calorimetric (DSC) Analysis Basedon Molecular Dynamics Simulation Taking base asphaltRMMA and RMMAFC as examples we can conclude fromTable 4 that the properties of RMMA and MA are roughlythe same while RMMAFC has obvious differences 1e totalendothermic peak energy of MA is 4308 Jg RMMA is3750 Jg and RMMAFC is 1281 Jg 1e smaller the en-dothermic peak energy is the more stable the properties ofasphalt are It can be seen from the degree and width of peakthat the heat absorption of asphalt is reduced and the peaktemperature is increased after red mud modification 1ethermal stability of asphalt is improved after red mudmodification and the rheological properties of asphalt arealso changed so that the temperature sensitivity of asphalt isreduced From the point of view of optimizing the perfor-mance of asphalt materials it is necessary to delay thethermal diffusion speed of asphalt molecules 1is requiresreducing the free volume of asphalt materials which can beachieved by adding inorganic materials or some macro-molecule materials so as to increase the ldquostiffnessrdquo of asphaltmaterials structure to a certain extent and to make asphaltmaterials 1e large voids in asphalt become smaller which

SU5000 50kV 83mm times 100k SE(L) 500nm

Figure 4 RMMAFC by electron microscopy

SU5000 50kV 77mm times 600 SE(L) 500microm

Figure 3 RMMA by electron microscopy

4 Advances in Materials Science and Engineering

200nm

ndash200nmHeight 40 microm

(a) (b)

Figure 5 AFM of MA

250 nm

ndash250 nmHeight 20 microm

(a) (b)

Figure 6 AFM of RMMA

250nm

ndash250nmHeight 40 microm

(a) (b)

Figure 7 AFM of RMMAFC

Advances in Materials Science and Engineering 5

restricts the synergistic movement of molecular chains inasphalt and achieves the purpose of reducing the thermalmotion range of asphalt molecules

35 Analysis of Red Mud-Asphalt Interface Energy Based onMolecular Dynamics Simulation In this paper the interfacemodel of asphaltene molecule on red mud surface wasconstructed by molecular simulation software (materialsstudio) 1e adsorption energy of red mud modified asphaltat mixing temperature and before and after freeze-thaw wasstudied by molecular dynamics simulation

1e models of asphaltene molecule (Figure 8) on twomain components of red mud Fe2O3 and Al2O3 wereestablished at minus10degC 25degC and 170degC (minus10degC is thetemperature in freeze-thaw cycles 25degC is the indoortemperature and 170degC is the heating temperature ofasphalt) 1rough the building tool in Materials Studiotoolbar the crystal plane of (0 0 1) is cut then severallayers of thickness are superimposed according to dif-ferent chemical composition and the crystal plane isoptimized by Geometry Optimization geometry structureoptimization tool in Forcite module At the same timeenergy is selected before the optimization of crystal planeis carried out 1e cell compass force field parameters aregiven by the necklace Under the NVT ensemble condi-tion the optimized interface model performs 200 PSdynamic calculation Given the initial position as arandom distribution the simulated temperatures areminus10degC 25degC and 170degC 1e Andersen temperaturecontrol method is used to control the temperature with atime step of 10 fs Finally a unit of Fe2O3 and anasphaltene with lattice parameters of a b 3021 A andc 431255 A was used As for the Al2O3 and anasphaltene a unit cell with dimension of a b 57108 Aand c 8660667 A was used 1e final bi-materials in-terface between asphaltene and two main components ofred mud (Fe2O3 and Al2O3) was built as shown inFigure 9

1erefore after the dynamic calculation of the in-terface model of asphaltene system on the chemicalcomposition surface of red mud the possible parametersof the interface can be obtained by the potential energy

calculation of each system of the interface model in turn[25 26] However in the process of dynamic simulationthe adsorption model with the lowest energy is neededfirst because the model with the lowest energy is usuallyconsidered as the optimal model of adsorption state andthe formula for calculating the interfacial interactionenergy is as follows

ΔE Einteraction Etotal minus Esurface + Easphalt1113872 1113873 (1)where Esurface is the total energy of the system when thelowest energy reaches the stable state after dynamics Easphaltis obtained by deleting the chemical composition of theunderlying aggregate and calculating the retained asphal-tene and ΔE represents the interaction energy betweenoxide interface and asphaltene interface

According to literature [26] the greater the negativevalue of the interaction energy ΔE between the chemicalcomposition of redmud and asphaltene in characterizing thestability of the adsorption system the greater the interactionbetween the chemical composition of red mud andasphaltene and the stronger the adsorption of asphaltene onthe surface of the chemical composition of red mud On thecontrary if ΔE is 0 or positive it indicates that asphaltenehas little or no adsorption on the surface of red mudchemical composition

From Table 5 the following can be concluded

(1) When asphaltene is in contact with the surface ofchemical composition of Fe2O3 and Al2O3 the re-sults of interfacial interaction energy are negativewhich indicates that there must be some adsorptionbetween asphaltene and the surface of chemicalcomposition of Fe2O3 and Al2O3

Table 3 Asphalt AFM image parameters analysis

Type R q (nm) R a (nm) KurtosisMA 210 171 257RMMA 486 249 242RMMAFC 150 094 149R q a root mean square roughness parameter Ra an arithmetic mean roughness kurtosis peak coefficient

Figure 8 Asphaltene molecular structure

Table 4 Test results of state transition process of asphalt

Asphalt Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Total heatabsorption (Jmiddotgminus1)

MA 1457 minus1515 minus2926sim51 2851 1912 51sim4367 4308RMMA 1119 minus1580 minus2906sim476 2631 1919 476sim4386 3750RMMAFC 0290 minus1999 minus2067simminus387 0991 2986 2237sim5421 1281

6 Advances in Materials Science and Engineering

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

33 Atomic Force Microscopic (AFM) AnalysisFigures 5ndash7 show AFM plots of MA RMMA and RMMAFCat room temperature From the AFM diagram of asphalt itcan be seen that the bee-structure of base asphalt is dense1e bee-structure decreases obviously with the addition ofred mud and the density of bee-structure decreases grad-ually but the bee-structure height increases obviously 1ebee-structure of RMMAFC is destroyed and its distributionis not uniform 1e polarity of asphalt mainly comes fromheterocyclic atoms in asphalt the bee-structure is mainlyaffected by the polarity of asphalt 1e asphaltene micelles inasphalt are not completely dispersed in the medium and thecontinuous phase is less After adding red mud powder thebee-structure in asphalt presents a long and large form andthe continuous phase increases 1is is because after addingred mud powder to base asphalt the light components inasphalt combine with red mud to form macromoleculewhich results in the change of the relative content of asphaltcomponents thus affecting the temperature sensitivity ofasphalt Compared with the RMMA and RMMAFC the bee-structure in asphalt area and dense are decreased Afterfreeze-thaw cycle red mud particles diffuse in asphalt toform smaller aggregates 1e content of components con-tinues to change in which the light components are dis-persed from the original structure under freeze-thaw actionand fused with small aggregates to form a new aggregate Atthe same time due to the action of salt solution the lightcomponents of modified asphalt becomemore which resultsin the weakening of the direct connection effect between redmud powder and asphalt matrix resulting in asphalt 1etemperature sensitivity becomes more sensitive and the lowtemperature performance decreases

In order to quantitatively characterize the roughness ofbase asphalt RMMA and RMMAFC the image informationof asphalt by AFM was further analyzed and counted 1ehigh root mean square roughness arithmetic mean devia-tion roughness and peak coefficient were selected as thecharacteristic parameters to evaluate the surface of asphaltRelevant information of base asphalt RMMA andRMMAFC was extracted and analyzed 1e results areshown in Table 3 Generally speaking the surface roughness

of RMMA is higher than that of MA and that of RMMAFCFor the index of peak coefficient usually when the peakcoefficient is less than 3 there are many peaks and valleys inthe image surface morphology when the peak coefficient ismore than 3 it shows that the image surface morphology isflat and there are not too many peaks and valleys Com-bining with the morphology of AFM the bee-structuredecreases obviously with the addition of red mud and thedensity of bee-structure decreases gradually but the bee-structure height increases obviously 1is is due to theswelling effect of red mud added into asphalt which iscaused by the adsorption of free components in asphalt byred mud particles 1e bee-structure of RMMAFC isdestroyed and its distribution is not uniform 1e red mud-asphalt matrix structure is destroyed after freeze-thaw cyclesresulting in poor connection between red mud and asphaltwhich also leads to a decline in the performance of RMMA

34 Differential Scanning Calorimetric (DSC) Analysis Basedon Molecular Dynamics Simulation Taking base asphaltRMMA and RMMAFC as examples we can conclude fromTable 4 that the properties of RMMA and MA are roughlythe same while RMMAFC has obvious differences 1e totalendothermic peak energy of MA is 4308 Jg RMMA is3750 Jg and RMMAFC is 1281 Jg 1e smaller the en-dothermic peak energy is the more stable the properties ofasphalt are It can be seen from the degree and width of peakthat the heat absorption of asphalt is reduced and the peaktemperature is increased after red mud modification 1ethermal stability of asphalt is improved after red mudmodification and the rheological properties of asphalt arealso changed so that the temperature sensitivity of asphalt isreduced From the point of view of optimizing the perfor-mance of asphalt materials it is necessary to delay thethermal diffusion speed of asphalt molecules 1is requiresreducing the free volume of asphalt materials which can beachieved by adding inorganic materials or some macro-molecule materials so as to increase the ldquostiffnessrdquo of asphaltmaterials structure to a certain extent and to make asphaltmaterials 1e large voids in asphalt become smaller which

SU5000 50kV 83mm times 100k SE(L) 500nm

Figure 4 RMMAFC by electron microscopy

SU5000 50kV 77mm times 600 SE(L) 500microm

Figure 3 RMMA by electron microscopy

4 Advances in Materials Science and Engineering

200nm

ndash200nmHeight 40 microm

(a) (b)

Figure 5 AFM of MA

250 nm

ndash250 nmHeight 20 microm

(a) (b)

Figure 6 AFM of RMMA

250nm

ndash250nmHeight 40 microm

(a) (b)

Figure 7 AFM of RMMAFC

Advances in Materials Science and Engineering 5

restricts the synergistic movement of molecular chains inasphalt and achieves the purpose of reducing the thermalmotion range of asphalt molecules

35 Analysis of Red Mud-Asphalt Interface Energy Based onMolecular Dynamics Simulation In this paper the interfacemodel of asphaltene molecule on red mud surface wasconstructed by molecular simulation software (materialsstudio) 1e adsorption energy of red mud modified asphaltat mixing temperature and before and after freeze-thaw wasstudied by molecular dynamics simulation

1e models of asphaltene molecule (Figure 8) on twomain components of red mud Fe2O3 and Al2O3 wereestablished at minus10degC 25degC and 170degC (minus10degC is thetemperature in freeze-thaw cycles 25degC is the indoortemperature and 170degC is the heating temperature ofasphalt) 1rough the building tool in Materials Studiotoolbar the crystal plane of (0 0 1) is cut then severallayers of thickness are superimposed according to dif-ferent chemical composition and the crystal plane isoptimized by Geometry Optimization geometry structureoptimization tool in Forcite module At the same timeenergy is selected before the optimization of crystal planeis carried out 1e cell compass force field parameters aregiven by the necklace Under the NVT ensemble condi-tion the optimized interface model performs 200 PSdynamic calculation Given the initial position as arandom distribution the simulated temperatures areminus10degC 25degC and 170degC 1e Andersen temperaturecontrol method is used to control the temperature with atime step of 10 fs Finally a unit of Fe2O3 and anasphaltene with lattice parameters of a b 3021 A andc 431255 A was used As for the Al2O3 and anasphaltene a unit cell with dimension of a b 57108 Aand c 8660667 A was used 1e final bi-materials in-terface between asphaltene and two main components ofred mud (Fe2O3 and Al2O3) was built as shown inFigure 9

1erefore after the dynamic calculation of the in-terface model of asphaltene system on the chemicalcomposition surface of red mud the possible parametersof the interface can be obtained by the potential energy

calculation of each system of the interface model in turn[25 26] However in the process of dynamic simulationthe adsorption model with the lowest energy is neededfirst because the model with the lowest energy is usuallyconsidered as the optimal model of adsorption state andthe formula for calculating the interfacial interactionenergy is as follows

ΔE Einteraction Etotal minus Esurface + Easphalt1113872 1113873 (1)where Esurface is the total energy of the system when thelowest energy reaches the stable state after dynamics Easphaltis obtained by deleting the chemical composition of theunderlying aggregate and calculating the retained asphal-tene and ΔE represents the interaction energy betweenoxide interface and asphaltene interface

According to literature [26] the greater the negativevalue of the interaction energy ΔE between the chemicalcomposition of redmud and asphaltene in characterizing thestability of the adsorption system the greater the interactionbetween the chemical composition of red mud andasphaltene and the stronger the adsorption of asphaltene onthe surface of the chemical composition of red mud On thecontrary if ΔE is 0 or positive it indicates that asphaltenehas little or no adsorption on the surface of red mudchemical composition

From Table 5 the following can be concluded

(1) When asphaltene is in contact with the surface ofchemical composition of Fe2O3 and Al2O3 the re-sults of interfacial interaction energy are negativewhich indicates that there must be some adsorptionbetween asphaltene and the surface of chemicalcomposition of Fe2O3 and Al2O3

Table 3 Asphalt AFM image parameters analysis

Type R q (nm) R a (nm) KurtosisMA 210 171 257RMMA 486 249 242RMMAFC 150 094 149R q a root mean square roughness parameter Ra an arithmetic mean roughness kurtosis peak coefficient

Figure 8 Asphaltene molecular structure

Table 4 Test results of state transition process of asphalt

Asphalt Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Total heatabsorption (Jmiddotgminus1)

MA 1457 minus1515 minus2926sim51 2851 1912 51sim4367 4308RMMA 1119 minus1580 minus2906sim476 2631 1919 476sim4386 3750RMMAFC 0290 minus1999 minus2067simminus387 0991 2986 2237sim5421 1281

6 Advances in Materials Science and Engineering

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

200nm

ndash200nmHeight 40 microm

(a) (b)

Figure 5 AFM of MA

250 nm

ndash250 nmHeight 20 microm

(a) (b)

Figure 6 AFM of RMMA

250nm

ndash250nmHeight 40 microm

(a) (b)

Figure 7 AFM of RMMAFC

Advances in Materials Science and Engineering 5

restricts the synergistic movement of molecular chains inasphalt and achieves the purpose of reducing the thermalmotion range of asphalt molecules

35 Analysis of Red Mud-Asphalt Interface Energy Based onMolecular Dynamics Simulation In this paper the interfacemodel of asphaltene molecule on red mud surface wasconstructed by molecular simulation software (materialsstudio) 1e adsorption energy of red mud modified asphaltat mixing temperature and before and after freeze-thaw wasstudied by molecular dynamics simulation

1e models of asphaltene molecule (Figure 8) on twomain components of red mud Fe2O3 and Al2O3 wereestablished at minus10degC 25degC and 170degC (minus10degC is thetemperature in freeze-thaw cycles 25degC is the indoortemperature and 170degC is the heating temperature ofasphalt) 1rough the building tool in Materials Studiotoolbar the crystal plane of (0 0 1) is cut then severallayers of thickness are superimposed according to dif-ferent chemical composition and the crystal plane isoptimized by Geometry Optimization geometry structureoptimization tool in Forcite module At the same timeenergy is selected before the optimization of crystal planeis carried out 1e cell compass force field parameters aregiven by the necklace Under the NVT ensemble condi-tion the optimized interface model performs 200 PSdynamic calculation Given the initial position as arandom distribution the simulated temperatures areminus10degC 25degC and 170degC 1e Andersen temperaturecontrol method is used to control the temperature with atime step of 10 fs Finally a unit of Fe2O3 and anasphaltene with lattice parameters of a b 3021 A andc 431255 A was used As for the Al2O3 and anasphaltene a unit cell with dimension of a b 57108 Aand c 8660667 A was used 1e final bi-materials in-terface between asphaltene and two main components ofred mud (Fe2O3 and Al2O3) was built as shown inFigure 9

1erefore after the dynamic calculation of the in-terface model of asphaltene system on the chemicalcomposition surface of red mud the possible parametersof the interface can be obtained by the potential energy

calculation of each system of the interface model in turn[25 26] However in the process of dynamic simulationthe adsorption model with the lowest energy is neededfirst because the model with the lowest energy is usuallyconsidered as the optimal model of adsorption state andthe formula for calculating the interfacial interactionenergy is as follows

ΔE Einteraction Etotal minus Esurface + Easphalt1113872 1113873 (1)where Esurface is the total energy of the system when thelowest energy reaches the stable state after dynamics Easphaltis obtained by deleting the chemical composition of theunderlying aggregate and calculating the retained asphal-tene and ΔE represents the interaction energy betweenoxide interface and asphaltene interface

According to literature [26] the greater the negativevalue of the interaction energy ΔE between the chemicalcomposition of redmud and asphaltene in characterizing thestability of the adsorption system the greater the interactionbetween the chemical composition of red mud andasphaltene and the stronger the adsorption of asphaltene onthe surface of the chemical composition of red mud On thecontrary if ΔE is 0 or positive it indicates that asphaltenehas little or no adsorption on the surface of red mudchemical composition

From Table 5 the following can be concluded

(1) When asphaltene is in contact with the surface ofchemical composition of Fe2O3 and Al2O3 the re-sults of interfacial interaction energy are negativewhich indicates that there must be some adsorptionbetween asphaltene and the surface of chemicalcomposition of Fe2O3 and Al2O3

Table 3 Asphalt AFM image parameters analysis

Type R q (nm) R a (nm) KurtosisMA 210 171 257RMMA 486 249 242RMMAFC 150 094 149R q a root mean square roughness parameter Ra an arithmetic mean roughness kurtosis peak coefficient

Figure 8 Asphaltene molecular structure

Table 4 Test results of state transition process of asphalt

Asphalt Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Total heatabsorption (Jmiddotgminus1)

MA 1457 minus1515 minus2926sim51 2851 1912 51sim4367 4308RMMA 1119 minus1580 minus2906sim476 2631 1919 476sim4386 3750RMMAFC 0290 minus1999 minus2067simminus387 0991 2986 2237sim5421 1281

6 Advances in Materials Science and Engineering

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

restricts the synergistic movement of molecular chains inasphalt and achieves the purpose of reducing the thermalmotion range of asphalt molecules

35 Analysis of Red Mud-Asphalt Interface Energy Based onMolecular Dynamics Simulation In this paper the interfacemodel of asphaltene molecule on red mud surface wasconstructed by molecular simulation software (materialsstudio) 1e adsorption energy of red mud modified asphaltat mixing temperature and before and after freeze-thaw wasstudied by molecular dynamics simulation

1e models of asphaltene molecule (Figure 8) on twomain components of red mud Fe2O3 and Al2O3 wereestablished at minus10degC 25degC and 170degC (minus10degC is thetemperature in freeze-thaw cycles 25degC is the indoortemperature and 170degC is the heating temperature ofasphalt) 1rough the building tool in Materials Studiotoolbar the crystal plane of (0 0 1) is cut then severallayers of thickness are superimposed according to dif-ferent chemical composition and the crystal plane isoptimized by Geometry Optimization geometry structureoptimization tool in Forcite module At the same timeenergy is selected before the optimization of crystal planeis carried out 1e cell compass force field parameters aregiven by the necklace Under the NVT ensemble condi-tion the optimized interface model performs 200 PSdynamic calculation Given the initial position as arandom distribution the simulated temperatures areminus10degC 25degC and 170degC 1e Andersen temperaturecontrol method is used to control the temperature with atime step of 10 fs Finally a unit of Fe2O3 and anasphaltene with lattice parameters of a b 3021 A andc 431255 A was used As for the Al2O3 and anasphaltene a unit cell with dimension of a b 57108 Aand c 8660667 A was used 1e final bi-materials in-terface between asphaltene and two main components ofred mud (Fe2O3 and Al2O3) was built as shown inFigure 9

1erefore after the dynamic calculation of the in-terface model of asphaltene system on the chemicalcomposition surface of red mud the possible parametersof the interface can be obtained by the potential energy

calculation of each system of the interface model in turn[25 26] However in the process of dynamic simulationthe adsorption model with the lowest energy is neededfirst because the model with the lowest energy is usuallyconsidered as the optimal model of adsorption state andthe formula for calculating the interfacial interactionenergy is as follows

ΔE Einteraction Etotal minus Esurface + Easphalt1113872 1113873 (1)where Esurface is the total energy of the system when thelowest energy reaches the stable state after dynamics Easphaltis obtained by deleting the chemical composition of theunderlying aggregate and calculating the retained asphal-tene and ΔE represents the interaction energy betweenoxide interface and asphaltene interface

According to literature [26] the greater the negativevalue of the interaction energy ΔE between the chemicalcomposition of redmud and asphaltene in characterizing thestability of the adsorption system the greater the interactionbetween the chemical composition of red mud andasphaltene and the stronger the adsorption of asphaltene onthe surface of the chemical composition of red mud On thecontrary if ΔE is 0 or positive it indicates that asphaltenehas little or no adsorption on the surface of red mudchemical composition

From Table 5 the following can be concluded

(1) When asphaltene is in contact with the surface ofchemical composition of Fe2O3 and Al2O3 the re-sults of interfacial interaction energy are negativewhich indicates that there must be some adsorptionbetween asphaltene and the surface of chemicalcomposition of Fe2O3 and Al2O3

Table 3 Asphalt AFM image parameters analysis

Type R q (nm) R a (nm) KurtosisMA 210 171 257RMMA 486 249 242RMMAFC 150 094 149R q a root mean square roughness parameter Ra an arithmetic mean roughness kurtosis peak coefficient

Figure 8 Asphaltene molecular structure

Table 4 Test results of state transition process of asphalt

Asphalt Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Heat absorption(Jmiddotgminus1)

Peaktemperature (degC)

Peak width(degC)

Total heatabsorption (Jmiddotgminus1)

MA 1457 minus1515 minus2926sim51 2851 1912 51sim4367 4308RMMA 1119 minus1580 minus2906sim476 2631 1919 476sim4386 3750RMMAFC 0290 minus1999 minus2067simminus387 0991 2986 2237sim5421 1281

6 Advances in Materials Science and Engineering

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

(2) Adsorption energy of asphaltene on the surface ofAl2O3 is the lowest at 25degC followed by minus10degC and170degC 1e adsorption capacity of asphaltene on thesurface of Fe2O3 is the lowest at minus10degC and theadsorption capacity is the highest at 25degC followedby 170degC

(3) 1e interfacial energy on the surface of Fe2O3 isrelatively small and the difference is not significantbut on the surface of Al2O3 the interfacial energy isvery obvious showing strong adsorption

1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface of redmud are negative According to the meaning of theformula of calculating the interfacial energy it can beseen that there are adsorption effects on the surface ofasphaltene and red mud 1rough the above analysis forred mud modified asphalt Al2O3 in red mud provides alarge number of adsorption interfaces for asphaltenewhile Fe2O3 in red mud contributes less to this partSecondly in low temperature environment the adsorp-tion effect of asphaltene in Fe2O3 and Al2O3 is weakerthan that in normal temperature 1erefore increasingthe content of Al2O3 or decreasing the content of Fe2O3 inred mud is beneficial to the adsorption of asphaltene 1esimulation studies the change of interfacial energy be-tween asphaltene and red mud 1e research findingspromote the fundamental understanding of modificationmechanism on the chemophysical and chemomechanicalrelationships of asphalt Further work will focus onsimulation of physical reaction by three components andfour components of asphalt materials using an integratedcomputational and experimental approach

4 Conclusion

Red mud was used as modified asphalt material to preparered mud modified asphalt and RMMAFC1eMA RMMAand RMMAFC were studied by scanning electron micros-copy (SEM) Fourier transform infrared spectrometry(FTIR) atomic force microscopy (AFM) and differential

scanning calorimetry (DSC) Microscopic experiments wereconducted to investigate the modification performance andmechanism 1e modification mechanism of red mudmodified asphalt was investigated using molecular dynamicssimulation in this study 1e results can be summarized asfollows

(1) Fourier transform infrared spectrometric (FTIR)analysis of MA RMMA and RMMAFC shows thatno new endothermic peaks are produced in Fouriertransform infrared spectrometry (FTIR) and theposition of characteristic endothermic peaks doesnot show obvious displacement indicating that nonew functional groups are produced and the ad-dition of red mud is not related to base asphaltChemical changes occur but there was a physicalblending process According to the results of scan-ning electron microscopy red mud as a modifier isuniformly fractionated in the asphalt in an inde-pendent form Differential scanning calorimetric(DSC) analysis showed that the heat absorption peakand heat absorption of modified asphalt decreasedafter red mud modification which indicated that thethermal stability of modified asphalt was improvedand the temperature sensitivity was reduced 1eheat absorption of modified asphalt with red mudwas greatly reduced by freeze-thaw cycle

(2) Atomic force microscopic (AFM) experiments showthat the three asphalts have bee-structure With theaddition of red mud the bee-structure decreasesobviously and the density of bee-structure decreasesgradually but the bee-structure height increasesobviously After freeze-thaw cycle the bee-structureof RMMA is destroyed its distribution is uneven

(a) (b)

Figure 9 Al2O3 and Fe2O3 adsorbed asphalt

Table 5 Interfacial energy of asphaltene in oxides

OxidesInterfacial energy Einteraction (kcalmol)

minus10degC 25degC 170degCFe2O3 minus1772 minus2214 minus2265Al2O3 minus319272 minus321809 minus311752

Advances in Materials Science and Engineering 7

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

and the red mud-asphalt matrix structure isdestroyed resulting in the poor connection betweenthe two

(3) 1e results of calculating the interfacial energy ofasphaltene on the chemical composition surface ofred mud are negative It can be seen that there areadsorption effects on the surface of asphaltene andred mud With the help of molecular dynamicssimulation the interfacial energy between asphalteneand red mud main components Fe2O3 and Al2O3 atminus10degC 25degC and 170degC is stronger than that ofFe2O3 1erefore increasing the content of Al2O3 ordecreasing the content of Fe2O3 in red mud isbeneficial to the adsorption of asphaltene

Data Availability

All data models and codes generated or used during thestudy are included within the article

Conflicts of Interest

1e authors declare no conflicts of interest

Acknowledgments

1is research was supported by grants from NationalNatural Science Foundation of China (Grants nos 51368015and 51768016) and Innovation Project of Guangxi GraduateEducation China (YCSW2020043)

References

[1] S Hussan M A Kamal I Hafeez N Ahmad S Khanzadaand S Ahmed ldquoModelling asphalt pavement analyzer rutdepth using different statistical techniquesrdquo Road Materialsand Pavement Design vol 21 no 1 pp 117ndash142 2020

[2] D A Gama J M Rosa Junior T J A de Melo andJ K G Rodrigues ldquoRheological studies of asphalt modifiedwith elastomeric polymerrdquo Construction and Building Ma-terials vol 106 pp 290ndash295 2016

[3] Q Zhang Y-h Xu and Z-g Wen ldquoInfluence of water-borneepoxy resin content on performance of waterborne epoxyresin compound SBR modified emulsified asphalt for tackcoatrdquo Construction and Building Materials vol 153pp 774ndash782 2017

[4] H Yu Z Leng Z Zhou K Shih F Xiao and Z GaoldquoOptimization of preparation procedure of liquid warm mixadditive modified asphalt rubberrdquo Journal of Cleaner Pro-duction vol 141 pp 336ndash345 2017

[5] C Fang R Yu S Liu and Y Li ldquoNanomaterials applied inasphalt modification a reviewrdquo Journal of Materials Science ampTechnology vol 29 no 7 pp 589ndash594 2013

[6] M Misık I T Burke M Reismuller et al ldquoRed mud abyproduct of aluminum production contains soluble vanadiumthat causes genotoxic and cytotoxic effects in higher plantsrdquoScience of the Total Environment vol 493 pp 883ndash890 2014

[7] D Dodoo-Arhin R A Nuamah B Agyei-TuffourD O Obada and A Yaya ldquoAwaso bauxite red mud-cementbased composites characterisation for pavement applica-tionsrdquo Case Studies in Construction Materials vol 7pp 45ndash55 2017

[8] I Panda S Jain S K Das and R Jayabalan ldquoCharacterizationof red mud as a structural fill and embankment material usingbioremediationrdquo International Biodeterioration amp Biodegra-dation vol 119 pp 368ndash376 2017

[9] H Wang B Behnia W G Buttlar and H Reis ldquoDevelop-ment of two-dimensional micromechanical viscoelastic andheterogeneous-based models for the study of block crackingin asphalt pavementsrdquo Construction and Building Materialsvol 244 p 118146 2020

[10] Z Li J Zhang S Li Y Gao C Liu and Y Qi ldquoEffect ofdifferent gypsums on the workability and mechanical prop-erties of red mud-slag based grouting materialsrdquo Journal ofCleaner Production vol 245 p 118759 2020

[11] T Hertel and Y Pontikes ldquoGeopolymers inorganic polymersalkali-activated materials and hybrid binders from bauxiteresidue (red mud)-putting things in perspectiverdquo Journal ofCleaner Production vol 258 p 120610 2020

[12] W Hu Q Nie B Huang X Shu and Q He ldquoMechanical andmicrostructural characterization of geopolymers derived fromred mud and fly ashesrdquo Journal of Cleaner Productionvol 186 pp 799ndash806 2018

[13] R Chen G Cai X Dong D Mi A J Puppala and W DuanldquoMechanical properties and micro-mechanism of loessroadbed filling using by-product red mud as a partial alter-nativerdquo Construction and Building Materials vol 216pp 188ndash201 2019

[14] Y Zhao N Liang H Chen and Y Li ldquoPreparation andproperties of sintering red mud unburned road brick usingorthogonal experimentsrdquo Construction and Building Mate-rials vol 238 p 117739 2020

[15] J Yang D Zhang J Hou B He and B Xiao ldquoPreparation ofglass-ceramics from red mud in the aluminium industriesrdquoCeramics International vol 34 no 1 pp 125ndash130 2008

[16] Z Zhao F Xiao and S Amirkhanian ldquoRecent applications ofwaste solid materials in pavement engineeringrdquo WasteManagement vol 108 pp 78ndash105 2020

[17] S Liu Z Li Y Li and W Cao ldquoStrength properties of Bayerred mud stabilized by lime-fly ash using orthogonal experi-mentsrdquo Construction and Building Materials vol 166pp 554ndash563 2018

[18] M A Khairul J Zanganeh and B Moghtaderi ldquo1e com-position recycling and utilisation of Bayer red mudrdquo Re-sources Conservation and Recycling vol 141 pp 483ndash4982019

[19] S Ccediloruh and O N Ergun ldquoUse of fly ash phosphogypsumand red mud as a liner material for the disposal of hazardouszinc leach residue wasterdquo Journal of Hazardous Materialsvol 173 no 1ndash3 pp 468ndash473 2010

[20] J Zhang P Li M Liang et al ldquoUtilization of red mud as analternative mineral filler in asphalt mastics to replace naturallimestone powderrdquo Construction and Building Materialsvol 237 p 117821 2020

[21] X Chen Y Guo S Ding et al ldquoUtilization of red mud ingeopolymer-based pervious concrete with function of ad-sorption of heavy metal ionsrdquo Journal of Cleaner Productionvol 207 pp 789ndash800 2019

[22] E Mukiza L Zhang X Liu and N Zhang ldquoUtilization of redmud in road base and subgrade materials a reviewrdquo Re-sources Conservation and Recycling vol 141 pp 187ndash1992019

[23] J Zhang S Liu Z Yao et al ldquoEnvironmental aspects andpavement properties of red mud waste as the replacement ofmineral filler in asphalt mixturerdquo Construction and BuildingMaterials vol 180 pp 605ndash613 2018

8 Advances in Materials Science and Engineering

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9

[24] Y Wang J Ye Y Liu X Qiang and L Feng ldquoInfluence offreeze-thaw cycles on properties of asphalt-modified epoxyrepair materialsrdquoConstruction and BuildingMaterials vol 41pp 580ndash585 2013

[25] G Xu and H Wang ldquoMolecular dynamics study of oxidativeaging effect on asphalt binder propertiesrdquo Fuel vol 188pp 1ndash10 2017

[26] G Xu and H Wang ldquoStudy of cohesion and adhesionproperties of asphalt concrete with molecular dynamicssimulationrdquo Computational Materials Science vol 112pp 161ndash169 2016

Advances in Materials Science and Engineering 9