Construction and Building Materials 71 (2014) 283–288

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Construction and Building Materials

journal homepage: www.elsevier .com/locate /conbui ldmat

Performance evaluation of nano-modified asphalt concrete

http://dx.doi.org/10.1016/j.conbuildmat.2014.08.0720950-0618/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +90 246 211 1226; fax: +90 246 237 12 83.E-mail addresses: sebnemsargin@sdu.edu.tr (S.S. Karahancer), melekkiristi@

gmail.com (M. Kiristi), serdalterzi@sdu.edu.tr (S. Terzi), mehmetsaltan@sdu.edu.tr(M. Saltan), ayseguloksuz@sdu.edu.tr (A.U. Oksuz), lutfioksuz@sdu.edu.tr (L. Oksuz).

1 Tel.: +90 246 211 1226; fax: +90 246 237 12 83.2 Tel.: +90 246 211 38 01; fax: +90 246 237 11 06.3 Tel.: +90 246 211 40 38; fax: +90 246 237 11 06.

Sebnem Sargin Karahancer a,⇑, Melek Kiristi b,2, Serdal Terzi a,1, Mehmet Saltan a,1,Aysegul Uygun Oksuz b,2, Lutfi Oksuz c,3

a Civil Engineering Department & Faculty of Engineering, Suleyman Demirel University, 32100 Central-ISPARTA, Turkeyb Chemistry Department, Faculty of Arts & Sciences, Suleyman Demirel University, 32100 Central-ISPARTA, Turkeyc Physics Department, Faculty of Arts & Sciences, Suleyman Demirel University, 32100 Central-ISPARTA, Turkey

h i g h l i g h t s

� Limestone mineral filler was modified by plasma processing.� Stability of asphalt mixtures increased after plasma modification.� Moisture susceptibility reduced after plasma modification.� MMA plasma modified samples showed better performance, relatively.

a r t i c l e i n f o

Article history:Received 17 April 2014Received in revised form 14 August 2014Accepted 24 August 2014

Keywords:Plasma modificationsHot mix asphaltNano materialsMarshall StabilityIndirect Tensile Strength

a b s t r a c t

Plasma modification method was used in order to increase the performance of the hot mix asphalt. Sur-face of mineral filler was modified by using three different components: methylmethacrylate (MMA),hexamethyldisiloxane (HMDSO) and silicon tetrachloride (SiCl4). Plasma modified mineral fillers withhot mix asphalts were evaluated by Marshall Stability (MS) and Indirect Tensile (IDT) Strength tests, com-paratively. According to the results, plasma modified samples showed higher stabilities and better prop-erties. Especially, tensile strength of MMA plasma modified sample exhibit increase of 30%. Eco-friendlyplasma modification technique provided homogenous, single step and fast processing for the modifica-tion of the asphalt materials.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Modified asphalt binders have been widely studied in the fieldof road construction. For this aim, innovative materials are promis-ing to improve the performance of the asphalt binders and asphaltmixtures. Up to now, styrene–butadiene–styrene (SBS), styrene–butadiene-rubber (SBR) and ethylene glycidyl acrylate (EGA) weremostly used in the asphalt modification effort [1]. These additivesin the base asphalt binder improved both anti-aging performanceof asphalt mixtures and reduced the moisture damage potentialin the low-temperature. In addition to that carbon fiber and crumbrubber were used as the asphalt binder and mixture, recently. For

instance, nano sized of SiO2 and SBS were used together for theasphalt modification and reported its better physical and mechan-ical properties after treatment [2].

Moreover, methylmethacrylate (MMA) was used as an asphaltadditive with aluminium trihydrate. Regarding to performance ofmodified asphalt mixtures, it was found that both additives consid-erably reduce moisture susceptibility and formation of ruts [3].

In the current study, plasma modification methods are intro-duced for hot mix asphalt (HMA) to increase the performance ofasphalt mixtures. Plasma is known as a fourth state of the materialand has variety of advantages as an eco-friendly surface coatingstechnology [4,5]. Plasma nanocoating is a solvent-free (dry), non-toxic, single-step process that provides thickness control rangingfrom tens of angstrom to micrometers [6]. All types of surfacecan be coated homogenously through plasma methods withdesired liquid and/or gaseous chemical without damaged thetargeted structures [7]. Generally, in plasma processing vapor ofa material is exposed to an electrical field so that ionization andexcitation are generated [8]. The chemical material or gaseous is

0 10 20 30 40 50 60 70 80 90

100

0,075 mm 0,180 mm 0,425 mm 2,00 mm 4,75 mm 9,5 mm

Perc

ent P

assin

g, b

y m

ass

Sieve size (mm)Limit Values (upper) Grada�on of Mix Limit values (lower)

Fig. 1. Gradation limits of the aggregates used in the study.

284 S.S. Karahancer et al. / Construction and Building Materials 71 (2014) 283–288

fragmented into reactive species (positive and negative ions,atoms, neutrals, metastables and free radicals) of plasma in orderto modify targeted structures [9]. In this study, mineral filler wasmodified by plasma coatings with MMA, HMDSO and SiCl4, andexamined comparatively. Performance, stability, flow values andspecific gravity parameters of plasma-modified asphalt mixtureswere evaluated with Marshall Stability (MS) and Indirect Tensile(IDT) Strength tests. In addition, structural and chemical character-istics of the materials were clarified by Scanning Electron Micro-scopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy.To the best of our knowledge, plasma modified asphalt mixtureshave not been reported yet. Hence, the study and results will bethe basis of the future related works.

2. Objectives and scope

The objective of the study is to obtain road construction mate-rial with the highest performance by using plasma-modifiedasphalt mixtures. Two types of plasma techniques were used as anew approach to coat homogenously of the surface of the lime-stone. These plasma techniques are radio frequency (RF:13.56 MHz) and microwave (MW: 2.45 GHz). Plasma phase wascreated in the plasma reactor by using three different materials:MMA, HMDSO and SiCl4, separately. During plasma processing ion-ized and excited vapor of these materials were coated around thelimestone particles in the reactor. These plasma coated materialsserved like a bridge around at limestone particles. Therefore,improved properties of the limestone were achieved after plasmamodification. Structural analyses were examined by FTIR andSEM studies. Besides, MS and IDT strength tests were conductedto assess the performance of plasma-modified asphalt mixtures.Standard aggregate gradation and 60–70 pen. asphalt binder wereused for producing all asphalt mixture samples.

3. Materials and methods

3.1. Aggregates and gradation

Aggregates used in the study were supplied from asphalt construction site ofmunicipal of Isparta. The nominal maximum aggregate size is 9.5 mm, and thewearing course design method was used for the mixtures. ‘‘Standard Test Methodsfor aggregate water absorption, saturated surface gravity and specific gravity’’ wasused to determine water absorption of the aggregate samples. In addition, ‘‘Stan-dard test method for aggregate abrasion loss (Los Angeles)’’ test was examined toevaluate the abrasion resistance of the aggregate samples. Aggregate propertieswere given in Table 1. Aggregate grading curves for asphalt mixtures were selectedin convenience with Turkish Highway Construction Specifications (Fig. 1).

3.2. Bitumen

Variety of standard tests were examined in order to determine properties ofbitumen. For instance, ASTM D5 [13] ‘‘Standard Test Method for penetration of bitu-men materials’’, ASTM D70 [14] ‘‘Standard Test Method for density of semi-flexiblebitumen materials (pycnometer method)’’, ASTM D36 [15] ‘‘Standard Test Methodfor softening point of bitumen (ring and ball apparatus)’’, ASTM D92 [16] ‘‘StandardTest Method for combustion and flash point with Cleveland open cup test appara-tus’’, ASTM D113 [17] ‘‘Standard Test Method for ductility of bitumen materials’’were used and assessed respectively. Test results were summarized in Table 2.

Table 1Properties of limestone aggregate used in the tests.

Sieve diameter Properties

4.75–0.075 mm Specific gravity (g/cm3)Saturated specific gravityWater absorption (%)

25–4.75 mm Specific gravity (g/cm3)Saturated specific gravityWater absorption (%)Abrasion loss (%) (Los Angeles)

3.3. Plasma modification of mineral filler

Surface modification of limestone mineral fillers was carried out in a Pyrex glasstube with RF and MW generators (Fig. 2). During the modification the Pyrex glasstube was evacuated down to a pressure of 2.6 Pa. Three modification agents wereused separately (MMA, HMDSO and SiCl4) and their vapors were flown into the tubewithout a precursor or any other auxiliary. FTIR (Perkin Elmer BX system, Beacons-field, Buckinghamshire, HP91QA, England) and SEM (Philips XL-30S FEG) analyseswere examined in order to investigate the effect of plasma processing onto asphaltmixtures.

The beginning of the study, RF plasma of HMDSO was used for the limestonecoating and resulted in low value according to the MS test. Therefore, MW plasmawas preferred for the all modifications because of its dense plasma phase. Durationof plasma modification process was increased from 30 to 60 min to investigate timeeffect onto modified samples.

3.4. Marshall stability test

In the study, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% (by the weight of 1245 g) asphaltbinders were examined in the asphalt mixture samples (totally twenty-one sam-ples) to determine the optimum bitumen content and the optimum one was5 wt%. First, plasma modified samples for 30 min (MMA–MW, HMDSO–MW andHMDSO–RF) and unmodified sample were selected. Then, each three fraction ofthem (totally twelve samples) were tested. After evaluation of first part, MW plas-ma modified samples for 1 h were used in order to investigate the effect of plasmaprocessing time. In this time, HMDSO species were eliminated because of their lowstabilities. MS test was examined with each three fraction of MMA–MW, SiCl4–MWand unmodified sample (totally nine samples) as a second part of the study. Allexperimental studies summarized in Fig. 3.

3.5. Indirect Tensile (IDT) Strength test

One commonly used parameter to evaluate asphalt mixtures is tensile strengthwhich can be used to quantify the effects of moisture and to determine the fractureresistance of an asphalt mixture. Typically, the tensile strength can be accuratelydetermined from an IDT strength test carried out in accordance with AASHTOTP9-02 [18].

The IDT strength test is a simple test that proposes to use currently availableequipment in most laboratories, being MS machine and a water bath set at 45 �C.

Loading configuration develops a relatively uniform tensile stress perpendicularto the direction of the applied load and along the vertical diametral plane, whichultimately causes the specimen to fail by splitting along the vertical diameter.Ensuring the test was carried out in a consistent manner, a testing procedure ofthe IDT Strength test was prepared [19].

In this study prior to the testing, the pats were measured according to the pro-cedure and were placed in the water bath for a period of conditioning of 30–40 minat a temperature of 45 �C. The test temperature of 45 �C was selected as it repre-sented the strength of asphalt at the high temperature range but below the soften-ing point of standard bitumen. Thus the working of the binder with the aggregate

Standard Limestone aggregate

ASTM C 127-88 [10] 2.6602.6520.130

ASTM C 128-88 [11] 2.3292.4282.800

ASTM C 131 [12] 20.38

Table 2Bitumen characteristics.

Bitumen characteristics

Test Average values Standard

Penetration (25 �C) 60–70 ASTM D5 [13]Flash point 180 �C ASTM D92 [16]Combustion point 230 �C ASTM D92 [16]Softening point 45.5 �C ASTM D36 [15]Ductility (5 cm/min) >100 cm ASTM D113 [17]Specific gravity 1.030 ASTM D70 [14]

S.S. Karahancer et al. / Construction and Building Materials 71 (2014) 283–288 285

structure was being tested, rather than just the aggregate structure itself as for MStest which tests at 60 �C. The specimens were then placed into the resilient modulusstyle loading jig which is placed within the MS machine to commence a load of theconstant speed to give a rate of travel of platen of 50 mm/min.

The IDT Strength test is provided in the test procedure which includes thecalculation for IDT Strength. Calculation of IDT Strength [19]:

Determining OBCs for different bitumenBC (2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5

Determining MS of different plasma-modified asPlasma Modification (30 min of MMA- MW, HMDSO

RF, SiCl4 - MW and 1 hour of MMA – MW, S

Determining IDT Strength of MMA plasma-modifiedPlasma modification (1 hour of MMA -

Max IDT Strength of MMA - MW plasma

modification

Fig. 3. Flow chart of l

Fig. 2. Plasma proc

St ¼2000F

3;14� ðhdÞ

where St is the Indirect Tensile Strength, kPa, F is the total applied vertical load atfailure, N, h is the Height of specimen, mm and d is the Diameter of specimen, mm.

In this study, three asphalt mixture samples were tested for each fraction ofMMA–MW for 1 h which is the best resulted sample and unmodified samples byIDT Strength test (totally six samples). A flowchart summarizing the experimentalstudy as given in Fig. 3.

4. Results and discussion

4.1. FTIR and SEM results

FTIR spectra was taken in order clarify of MMA–MW modifiedlimestone which is the best-resulted sample (Fig. 4). There are sev-eral species appear during the plasma process such as fragments,radicals and ions because of high electron energy density. Therefore,

rates%)

phalt mixtures – MW, HMDSO – iCl4 - MW)

asphalt mixturesMW)

BC: Bitumen ContentOBC: Optumun Bitumen ContentMS: Marshall StabiltyIDT: Indirect Tensile StrengthMMA: MethylmethacrylateHMDSO: HexamethyldisyloxaneSiCl4: Silicon tetrachlorideMW : MicrowaveRF : Radio Frequency

OBC 5%

Max MS MMA -MW

aboratory works.

essing set up.

Fig. 4. FTIR spectra of plasma modified MMA–MW and limestone.

286 S.S. Karahancer et al. / Construction and Building Materials 71 (2014) 283–288

randomly occurred cross-linked structures take place at aroundlimestone particles without any degradation. There was no sig-nificant change on characteristic peaks of limestone after modifica-tion. The presence of FTIR absorption peaks at different frequencieslike 874 cm�1, 1434 cm�1, 2518 cm�1 and 2874 cm�1 which areidentified for mineral in the samples. The peaks at 874 cm�1 and708 cm�1 belong to the C@O stretching and CAH vibration, respec-tively [20]. The frequency at 1434 cm�1 is due to (CO3)2 stretchingmode vibration and the band at �3444 cm�1 corresponds to OAH

Limestone unmodified

Fig. 5. SEM image of MMA–MW plasma-mod

Fig. 6. Change in Dp and Dt for different

stretching vibrations in water and hydroxyl groups in variousorganic and inorganic substances [21]. Additional peak appearedat around 3642 cm�1 after plasma modification. It can be attributedthe OAH stretching mode vibration depending on the increasedfunctionalization [22]. Organic carbon is present in almost all thesamples, which have frequency at 2874 cm�1.

The expected morphology of MMA–MW plasma modified lime-stone sample is observed by SEM analyses. From the SEM images(Fig. 5), space-filling and dense morphology is observed afterMMA–MW plasma-modified limestone sample.

4.2. Marshall stability test results

Average practical specific gravity (Dp), average theoreticalspecific gravity (Dt), void percentages (Vf), void volume values(Vh), voids in mineral aggregate (VMA), stability and flow valueswere obtained from the test results. Graph of Dp and Dt resultsare illustrated in Fig. 6. According to the graph, different plasmamodifications did not affect the Dp and Dt results significantly.

Vh, VMA and Vf results of all samples are illustrated in Figs. 7and 8. Vh value was obtained as 7.1%, 3.36%, 6.61% and 2.67% forunmodified limestone, HMDSO–MW, HMDSO–RF and MMA–MW,respectively. Besides, Vf value was obtained as 59.86%, 74.22%,58.75%, 74.34% for limestone, HMDSO–MW, HMDSO–RF andMMA–MW, respectively.

VMA value was obtained as 17.64%, 14.64% 17.81% 14.63% forunmodified limestone, HMDSO–MW, HMDSO–RF, MMA–MW,respectively. It was observed that VMA value of MMA–MWdecreased.

MMA - MW plasma modified

ified for 1 h and unmodified limestone.

plasma-modified asphalt mixtures.

Fig. 7. Change in Vh and Vf for different plasma-modified asphalt mixtures.

Fig. 9. Flow values for plasma-modified asphalt mixtures.

Fig. 10. Marshall stability results for plasma-modified asphalt mixtures.

Fig. 11. Marshall stability test results.

Fig. 12. IDT strength test results for MMA plasma-modified and limestone asphaltmixtures.

Fig. 8. Voids in mineral aggregate (VMA) graph.

S.S. Karahancer et al. / Construction and Building Materials 71 (2014) 283–288 287

Fig. 9 represents flow values for modified and unmodified sam-ples. Flow values approve limit values according to TechnicalSpecifications of Highways and it reflects the plasticity and flexibil-ity properties of asphalt mixtures. Flow values have a linearinverse relationship with internal friction.

As a result, MS value was obtained as 1242 kg, 1112 kg, 1000 kg,1222 kg for limestone, HMDSO–MW, HMDSO–RF, MMA–MW,respectively. The MMA–MW resulted in the highest value compar-ing to the other plasma modified samples (Fig. 10).

As shown in Fig. 11, MS value was obtained as 886 kg, 1050 kg,1030 kg and 853 kg for limestone, MMA–MW, SiCl4–MW 1 h andSiCl4–MW 30 min, respectively. It is clear that MMA–MW hasshown the best stability.

4.3. Indirect Tensile (IDT) Strength test

IDT Strength test was carried out in order to assess MMA–MWplasma-modified sample which is the best-resulted sample. Fig. 12

Fig. 13. IDT Strength vs Air Voids for limestone and MMA–MW plasma-modified samples.

288 S.S. Karahancer et al. / Construction and Building Materials 71 (2014) 283–288

shows the IDT Strength for MMA–MW and unmodified limestone.In view of IDT strength, MMA–MW plasma-modified asphalt mix-tures were higher than 30% of unmodified limestone samples.

The moisture susceptibility of the asphalt mixtures reducesthrough the modification of mineral filler because of increasementof the air voids. Besides, the strength of the plasma-modifiedasphalt mixtures can also be improved. Fig. 13 shows the IDTstrength vs. air voids (%) for plasma-modified samples in compar-ison with unmodified limestone. It is seen that the non-uniformvoid distribution of the asphalt mixture played a significant rolein producing a round of problematic Indirect Tensile Strength inwhich the specimens prepared at 5% bitumen content.

5. Conclusions

Limestone mineral filler was modified by MW (2.45 GHz) andRF (13.56 MHz) plasma discharges without using extra solventand precursor agents. Plasma processing supplied homogeneity,easy, fast and controllable modification for the study. The impactsof MMA, HMDSO and SiCl4 plasma modification to the limestonewere evaluated comparatively in the HMA mixtures. The laborato-ry tests (IDT strength and MS) examined and the following conclu-sions is obtained:

1. Plasma modification is a useful and eco-friendly technique toobtain the improved asphalt mixtures.

2. Surface area of the limestone has increased after plasmamodification.

3. Moisture susceptibility of the asphalt mixtures reduced becauseof the increased air voids.

4. IDT strength and MS results showed that MMA–MW plasma-modified asphalt mixture is higher than that of 30% the unmo-dified and other plasma modified asphalt mixtures.

5. Future work will be focused on additional performance tests ofthe plasma-modified asphalt mixtures and further studiesregarding to plasma modified road construction materials.

Acknowledgement

This project has been supported by TUBITAK (Scientific andTechnological Research Council of Turkey) under the Project Num-ber: 112M182.

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