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Journal of Hazardous Materials 279 (2014) 302–310

Contents lists available at ScienceDirect

Journal of Hazardous Materials

jo ur nal ho me p ag e: www.elsev ier .com/ locate / jhazmat

n approach to the usage of polyethylene terephthalate (PET) wastes roadway pavement material

etin Gürüa,∗, M. Kürs at C ubukb, Deniz Arslanb, S. Ali Farzanianb, Ibrahim Bilici c

Gazi University, Eng. Fac., Chem. Eng. Depart., 06570 Maltepe-Ankara, TurkeyGazi University, Eng. Fac., Civil Eng. Depart., 06570 Maltepe-Ankara, TurkeyHitit University, Eng. Fac., Chem. Eng. Depart., 19100 C orum, Turkey

i g h l i g h t s

We derived two novel additive mate-rials from PET bottle waste: TLPP andVPP.We used them to modify the baseasphalt separately.The additives improved both theasphalt and the asphalt mixture per-formance.TLPP, VPP offer a beneficial way aboutdisposal of ecologically hazardousPET waste.

g r a p h i c a l a b s t r a c t

800

840

880

920

960

1000

1040

5.554.54

Asphalt Content (%)

Mar

shal

l S

tab

ilit

y (

kg

)..

0% (w/w) VPP 1% (w/w) VPP 2% (w/w) VPP

3% (w/w) VPP 5% (w/w) VPP 10 % (w/w) VPP

r t i c l e i n f o

rticle history:eceived 4 April 2014eceived in revised form 13 June 2014ccepted 10 July 2014vailable online 18 July 2014

eywords:odified asphalt

olyethylene terephthalate

a b s t r a c t

This study investigates an application area for Polyethylene Terephthalate (PET) bottle waste which hasbecome an environmental problem in recent decades as being a considerable part of the total plasticwaste bulk. Two novel additive materials, namely Thin Liquid Polyol PET (TLPP) and Viscous Polyol PET(VPP), were chemically derived from waste PET bottles and used to modify the base asphalt separately forthis aim. The effects of TLPP and VPP on the asphalt and hot mix asphalt (HMA) mixture properties weredetected through conventional tests (Penetration, Softening Point, Ductility, Marshall Stability, NicholsonStripping) and Superpave methods (Rotational Viscosity, Dynamic Shear Rheometer (DSR), Bending BeamRheometer (BBR)). Also, chemical structures were described by Scanning Electron Microscope (SEM)

hin Liquid Polyol PETiscous Polyol PETatiguetripping resistance

equipped with Energy Dispersive Spectrometer (EDS) and Fourier Transform Infrared (FTIR) techniques.Since TLPP and VPP were determined to improve the low temperature performance and fatigue resistanceof the asphalt as well as the Marshall Stability and stripping resistance of the HMA mixtures based onthe results of the applied tests, the usage of PET waste as an asphalt roadway pavement material offersan alternative and a beneficial way of disposal of this ecologically hazardous material.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

Plastics create considerable amount of solid waste in the worldue to their usage in many areas of our lives like packaging, buildingnd construction, automotive, electric and electronic applications.

∗ Corresponding author. Tel.: +90 312 5823555; fax: +90 312 2308434.E-mail address: mguru@gazi.edu.tr (M. Gürü).

ttp://dx.doi.org/10.1016/j.jhazmat.2014.07.018304-3894/© 2014 Elsevier B.V. All rights reserved.

They are synthetic materials derived mainly from petroleum ornatural gas and composed substantially of carbon, hydrogen andoxygen combinations. Since they have high decomposition tem-perature, high resistance to ultraviolet radiation and are mostlynot biodegradable, they can remain on both land and sea for

years causing environmental pollution. Plastics tend to break intosmaller fragments called macro/meso/micro-plastics which havespecific and significant set of impacts on ecosystem and can affecthuman and animal health negatively associated with their chemical

rdous Materials 279 (2014) 302–310 303

stc

atSvtimosa

nptthmPiSaasarawt(RMwwfifMsbaao

batwbTdno

TP

Table 2Descriptive properties of the aggregate.

Test Value

Los Angeles abrasion, % 9.2MgSO4 freezing loss, % 0.16Flakiness index, % 14.5Methylene blue 1.5Water absorption, % 2.11Coarse aggregate specific gravity (g/cm3), bulk 2.643Apparent 2.709Fine aggregate specific gravity (g/cm3), bulk 2.732Apparent 2.778

dried 8 h at 105 C. The glycolysis reactions of PET were carriedout in a 1 L five-necked flask equipped with stirrer, thermocou-ple and refluxing condenser unit under nitrogen atmosphere toavoid oxidation. The established glycols, PET and catalyst (0.02% of

80

100

)

Type-1 Gradation limitsAggregate gradation

ASTM Sieves 200 80 40 10 4 3/8" 1/2" 3/4"

M. Gürü et al. / Journal of Haza

tructure. Toxic chemicals within the plastic can bioaccumulate uphe food chain through ingestion by wildlife meaning that humanan also be subjected to those chemicals.

Plastics are used by almost all end-use segment of the economynd their usage is quite likely to increase with the developments inhe plastic industry, which in turn causes increase of plastic wastes.ince they are found to alter the working of ecosystem [1–3], pre-ention/minimization of plastic becoming waste and recovery ofhis ecologically hazardous waste should be taken into accountnstead of being left freely in nature or landfilled. Available waste

anagement systems include recycling and/or energy recoveryperations, but they need to be improved more. New policieshould thus be developed before plastic waste becomes an unsolv-ble problem.

Being lighter, more durable and less bulky than many alter-ative materials, one of the main application and so the mainost-consumer waste for plastics is packaging and polyethyleneerephthalate (PET) bottles generate considerable part of this sec-or. PET has exceptional gas and moisture barrier properties withigh shatter resistance and can contain carbon dioxide whichakes it ideal for use in water and beverage bottles. Single-use

ET bottles have a short service life and therefore turn into res-dential (post-consumer) plastic waste in a short period of time.ince PET recycling has not been carried out in the same amounts its production [4,5], it would be worthwhile to find out newpplication areas for PET bottle wastes to maximize their end-of-ervice life management effectiveness. The usage of PET waste as

reinforcement component for asphalt concrete pavement mate-ial, Hot Mix Asphalt (HMA), can be a research area for such anim which is still in its infancy. In the previous studies, PET wasteas generally added to the asphalt mixture with dry process (mix-

ure modification) or used as aggregate in the asphalt mixtureaggregate replacement) in order to improve HMA performance.esearches have shown that permanent deformation resistance,arshall Stability, stiffness and fatigue life of the asphalt mixturesere increased while moisture damage resistance was decreasedhen PET was used as additive in the mixture (mixture modi-cation) [6–9]. The replacement of aggregate with PET was also

ound to increase permanent deformation resistance but decreasearshall Stability and stiffness of the mixtures [10,11]. However,

pecific gravity of the asphalt mixtures was found to be decreasedy either method [7,11]. Different from the mentioned studiesbove, asphalt was modified with additive derived from PET byminolysis and found to improve the Marshall Stability dependingn the asphalt and additive contents [12].

The selected additive can be incorporated to the asphalt mixturey dry process or wet process. The dry process covers mixing thedditive with aggregates prior to adding the binder to the mix-ure while wet process refers to the modification of the binderith the additive at an elevated temperature prior to adding the

inder to the mixture. In this study, two novel additive materials,hin Liquid Polyol PET (TLPP) and Viscous Polyol PET (VPP), were

erived chemically from PET bottle wastes. This paper presents aovel approach about the incorporation of PET waste in the formf TLPP and VPP to HMA mixtures by means of a feasible wet

able 1hysical properties of the base asphalt.

Test Value Standard

Specific gravity, 25 ◦C (g/cm3) 1.02 ASTM D-70Penetration 25 ◦C, 100 g, 5 s (0.1 mm) 45 ASTM D-5Softening point (◦C) 51.5 ASTM D-36Viscosity, 130 ◦C (Pa s) 0.186 ASTM D-4402140 ◦C (Pa s) 0.126 ASTM D-4402Ductility, 15 ◦C (cm) +105 ASTM D-113

Filler specific gravity (g/cm3), bulk –Apparent 2.823

process and investigates the effects of PET waste both onasphalt and on HMA mixture performances through conventionaltests (Penetration, Softening Point, Ductility, Marshall Stability,Nicholson Stripping) and Superpave methods (Rotational Viscos-ity, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer(BBR)). Also, chemical structures were described by results of SEMequipped with EDS and FTIR instruments.

2. Materials and methodology

2.1. Asphalt and aggregate

The base asphalt was sourced from Kırıkkale/Turkey PetroleumRefinery and used throughout the study. Table 1 displays the phys-ical properties of the base asphalt.

100 percent crushed basalt aggregate was used to manufacturethe asphalt mixtures. The descriptive properties of the aggregatewere given in Table 2. Gradation characteristics of the aggregateused in Marshall Test samples were shown in Fig. 1 which are theaverage values of the Type-1 wearing course gradation limits ofTurkey’s Highway Technical Specification.

2.2. Preparation of synthetic PET additives

PET waste consisting post-consumer soft-drink bottles wascollected from environment. Collected PETs were purged from con-taminants such as PVC, labels and cut by shredder into small piecesas flake under 10 mm sieve. The flakes were washed with soup and

◦

1001010.10.01Sieve Size (mm), Log

0

20

40

60

Per

cent

Pas

sing (

%

Fig. 1. Gradation characteristics of the Marshall Test samples and specification lim-its.

304 M. Gürü et al. / Journal of Hazardous Materials 279 (2014) 302–310

ctions

PAw2daP

itDaaad(p6f

2

pwamo1

2

SmtaRdsrm1btfRGr

Fig. 2. Additives derived from PET bottle waste by glycolysis rea

ET) were placed in the reactor. Propylene glycol (PG), supplied byklar Kimya, and titanium IV butoxide (TBT), supplied by Aldrich,ere used as glycol and catalyst. Experiments were carried out at

20 ◦C and the reaction was ended when the last piece of PET wasisappeared. Glycolized products, shown in Fig. 2, were labeledccording to the moiety of PET which is 1:2 for Thin Liquid PolyolET (TLPP) and 1:1 for Viscous Polyol PET (VPP).

The acid number is defined as the amount of potassium hydrox-de required to neutralize 1.00 g of polyol and determined byitration of the sample solution with 0.1 N KOH solutions (ASTM3644). During the glycolysis reactions, acid number was measuredt 1 h intervals. The hydroxyl number (OH number) is defined as themount of potassium hydroxide equivalent to the amount of aceticcid involved in the esterification reaction with 1.00 g of polyol andetermined by the conventional acetic anhydride/pyridine methodASTM D4662-03). Acid numbers and OH number of glycolyzedroducts (TLPP and VPP) were recorded as 16.4 and 430 for TLPP,.7 and 340 for VPP, respectively which were found to be properor the glycolysis reaction of PET with PG.

.3. Modification of asphalt with PET additives

Each additive was added to the base asphalt at five different pro-ortions: 1%, 2%, 3%, 5% and 10% by asphalt mass. The base asphaltas put into a metal container and heated to 120 ◦C in an oven

nd then the selected additive (TLPP or VPP) was added as above-entioned proportions. Modification process was performed in an

il bath at 120 ◦C by blending the base asphalt and the additive for0 min with a mechanical four-armed mixer rotating at 1300 rpm.

.4. Methodology

This study includes the results of a group of conventional anduperpave test methods in order to evaluate the effects of PETodification on the asphalt and HMA mixture performances. Rota-

ional viscosity tests were applied on the base and PET modifiedsphalt samples according to ASTM D-4402 using Brookfield DV IIIheometer with spindle no. 29. Penetration, softening point anductility of the asphalt samples with and without PET were mea-ured in accordance with ASTM D-5, ASTM D-36 and ASTM D-113,espectively. Softening point tests were performed with EL46-4502odel ring and ball apparatus. Ductility tests were carried out at

5 ◦C. Complex shear modulus (G*) and phase angle (ı) values of thease and modified asphalt samples were measured through DSRests at 64 ◦C, 70 ◦C for rutting characteristics and 28 ◦C, 25 ◦C for

atigue characteristics with respect to AASHTO T315 using Geminiheometer (Bohlin Instrument) with 10 rad/s (1.59 Hz) frequency.* and ı were used as G*/sin ı and G* sin ı to compare ruttingesistance and fatigue resistance of the asphalt samples. BBR tests

; (a) Thin Liquid Polyol PET (TLPP); (b) Viscous Polyol PET (VPP).

(AASHTO T313) were carried out with Thermoelectric BBR Instru-ment (Cannon) at −6 ◦C, −12 ◦C and −18 ◦C through which the creepstiffness (S) and creep ratio (m) values of the base and modifiedasphalt samples were determined in order to evaluate low tem-perature performance of the asphalt samples. The effect of PETon the mechanical properties of the HMA mixtures were detectedthrough Marshall Test (ASTM D1559) and Nicholson Stripping test(ASTM D1664). Marshall Test samples were produced with 1150 gbasalt aggregate and compacted by 75 blows on each side withMarshall Compactor device (EL45-6600). The stripping resistancesof the mixtures with and without PET were examined with Nichol-son stripping test. The coarse basalt aggregate (6.3–9.5 mm) wascoated with base and PET modified asphalts separately at 110 ◦Cand then immersed in distilled water at 60 ◦C for 24 h without anycompaction. The stripping resistance of each mixture was visuallydetermined and the effect of PET on the adhesive bond strengthat the asphalt-aggregate interface was evaluated. The chemicalchanges on the base asphalt arisen from the PET modification wereexamined by FTIR between 400 and 4000 cm−1 using Jasco 480 plusmodel test device. FTIR test samples were produced with KBr under7 tons pressure. SEM images of the asphalt samples were recordedwith JEOL 6360 model SEM (equipped with EDS) apparatus throughwhich the chemical differences between the test samples were dis-cussed.

3. Results and discussion

3.1. Evaluation of viscosity test results

Viscosity is a fundamental characteristic of any asphalt anddefines the flow resistance of the material at a certain tempera-ture. Related with the fabrication and construction temperaturesof HMA, viscosity tests were applied between 90 ◦C and 160 ◦Cand the results were presented in Fig. 3 as a function of additiveconcentration.

The viscosity of the base asphalt was found to be decreased atall test temperatures by the increase of TLPP concentration. Thedecrement has reached to 32.5% at 160 ◦C for 10% (w/w) show-ing that TLPP can keep its effectiveness at high temperatures andallows to lower asphalt plant working temperature like organic-based synthetic asphalt modifier compounds [13–15] and WarmMix Asphalt (WMA) additives [16,17]. When the optimum asphaltviscosity of 0.2 Pa s is considered during HMA mixture fabrication[18], it is clear from Fig. 3b that TLPP can reduce plant temperatureup to 3.5 ◦C (from 130 ◦C to 126.5 ◦C) through which the heat energy

required for the fabrication of HMA mixtures, the short-term agingof asphalt and the emissions produced from the asphalt plant willalso be reduced but not much as WMA additives do. Similar vis-cosity results, except for the concentration rate of 1% (w/w), were

M. Gürü et al. / Journal of Hazardous Materials 279 (2014) 302–310 305

109876543210

Additive Concentration (% w/w)

0.32

0.36

0.40

0.44

0.48

0.80

0.90

1.00

1.10

1.20

Vis

cosi

ty (

Pa.

s)

1.80

2.00

2.20

2.40

4.40

4.60

4.80

5.00

5.20VPP Modified Asphalt

TLPP Modified Asphalt

90oC

100oC

110oC

120oC

,

,

,

109876543210

Additive Concentration (% w/w)

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Vis

cosi

ty (

Pa.

s)

VPP Modified Asphalt

TLPP Modified Asphalt

130oC

140oC

150o C

160oC

lts; (a

oadhapwt

3r

tfp(fbi[cta

TP

w

(a)

Fig. 3. Viscosity test results of the base and modified aspha

btained by VPP modification. 1% (w/w) VPP has resulted smallmounts of increases on viscosity varying between 0.4% and 5.4%ue to increased cohesion of asphalt at low VPP amounts whereasigher VPP concentrations decreased viscosity up to 21.1%. VPPlso keeps its effectiveness at high temperatures and as the tem-erature increases, in general, the viscosity-reducing effect of VPPas observed to increase (Fig. 3) leading to reduce the fabrication

emperature of HMA mixtures like TLPP.

.2. Evaluation of penetration, softening point and ductility testsesults

Table 3 exhibits the penetration, softening point and ductilityests results of the base and modified asphalt samples. As expectedrom the previous test, penetration was increased and softeningoint was decreased by TLPP and VPP modifications except 1%w/w) of VPP. These parameters were found to stay at the same levelor 1% (w/w) VPP. The ductility property was not changed by TLPPut decreased with the increasing content of VPP which can be seen

n literature studies carried out with different asphalt additives

19,20]. Softer asphalts may be less susceptible to low temperatureracking and thus preferred to use in cold regions in terms of bet-er low temperature cracking property as they become less hardent low temperatures. So, TLPP and VPP modified asphalts were

able 3enetration, softening point and ductility tests results.

Asphalt Penetration(0.1 mm)

Softeningpoint (◦C)

Ductility @15 ◦C (cm)

Base asphalt 45 51.5 +105a

TLPP modified asphalt, 1% (w/w) 51 48.7 +105a

2% (w/w) 54 48.3 +105a

3% (w/w) 55 48.1 +105a

5% (w/w) 56 47.9 +105a

10% (w/w) 61 47.5 +105a

VPP modified asphalt, 1% (w/w) 45 51.6 +105a

2% (w/w) 50 50.3 843% (w/w) 54 50.1 775% (w/w) 57 50.0 6810% (w/w) 60 49.8 55

a The measuring capacity of the ductility test device was 105 cm and the sampleas not broken in the test.

(b)

) between 90 ◦C and 120 ◦C; (b) between 130 ◦C and 160 ◦C.

expected to show improved performance at cold climate regionsdue to the decreased viscosity and softening point and increasedpenetration.

3.3. Evaluation of BBR and DSR test results

The effects of TLPP and VPP modifications on the low, mediumand high temperature performance of the base asphalt weredetected through BBR and DSR tests. Laboratory facility limitationsmade us reduce the number of test samples. The most effectiveand remarkable amounts of each additive performing significantchanges on asphalt rheology were determined from Fig. 3 as 3%(w/w) TLPP, 5% (w/w) TLPP, 1% (w/w) VPP and 2% (w/w) VPP andhave been selected to compare with the base asphalt.

Creep stiffness (S) and creep rate (m) values of the PAV-agedasphalt samples were determined from BBR tests and the resultswere graphically summarized in Figs. 4 and 5. According to theSuperpave binder specification, S should not exceed 300 MPa andm should be at least 0.3. All the test samples provided these lim-itations at −6 ◦C and −12 ◦C but none of them was successful at−18 ◦C. Asphalt with lower S and higher m performs better at lowtemperatures in terms of low temperature cracking resistance. Asseen from Figs. 4 and 5, S was decreased by both of the additives atall test temperatures while m was increased by 3% (w/w) TLPP and1% (w/w) VPP, reduced slightly with 2% (w/w) VPP and stayed aboutat the same level with 5% (w/w) TLPP modifications. As lower S andhigher m is desired, asphalt with lower S/m value can be said to havemore low temperature cracking resistance [13,14]. S/m values of thebase asphalt at different temperatures were found to be decreasedranging from 0.9% to 29.8% (Table 4) showing the improved perfor-mance of the TLPP and VPP modified asphalts at low temperatures.Besides, 3% (w/w) TLPP modified asphalt gave better S/m values atall test temperatures among the compared asphalt samples.

DSR tests were conducted on the original (unaged), RTFOT-agedand PAV-aged asphalt samples in order to determine the complexshear modulus (G*) values and phase angles (ı) (Table 5) to usein rutting and fatigue evaluation. G* is the total resistance of the

asphalt sample against deformation and can be considered as themeasure of the asphalt stiffness. ı defines the elastic/viscous behav-ior of the asphalt at the testing temperature. ı ranges between 0◦

and 90◦ and the lower the ı, the more elastic the asphalt is. Lower ı

306 M. Gürü et al. / Journal of Hazardous Materials 279 (2014) 302–310

Fig. 4. BBR test results (creep stiffness).

t results (m-value).

imurstrwfiw1tNfct2vvoob6

Table 4S/m values of the asphalt samples with and without additive.

S/m

−6 ◦C −12 ◦C −18 ◦C

Base asphalt 314.8 695.0 1902.03% (w/w) TLPP modified asphalt 240.2 567.6 1335.85% (w/w) TLPP modified asphalt 261.4 678.2 1812.7

Fig. 5. BBR tes

s desirable for better rutting and fatigue resistances. TLPP and VPPodifications, in general, were found to reduce ı insignificantly for

naged and RTFOT-aged samples. Asphalt should be stiff/elastic toesist deformation (rutting) whereas should be elastic and not tootiff to resist fatigue cracking. As can be seen in Table 5, modifica-ions decreased G*, except for 1% (w/w) VPP, resulting to reduceutting resistance parameter (G*/sin ı) which can also be obtainedith the other viscosity-reducing asphalt modifiers [13–15]. Con-rming the previous tests results, a small increment in G*/sin ıas obtained with 1% (w/w) VPP. Minimum of G*/sin ı should be

.00 kPa and 2.20 kPa for unaged and RTFOT-aged samples, respec-ively. All the tested samples fulfilled these limitations at 64 ◦C.one of them was found to be sufficient at 70 ◦C. G*x sin ı is the

atigue resistance parameter derived by Superpave binder specifi-ation to a maximum value of 5000 kPa for PAV-aged samples. All ofhe tested samples met the fatigue criteria of G*x sin ı ≤ 5000 kPa at8 ◦C. TLPP and VPP modifications were found to decrease G*x sin ıalue of the base asphalt significantly (Table 5). Since too stiff andiscous asphalts are sensitive to fatigue cracking, TLPP and VPP

ffer improved fatigue cracking resistance by decreasing G*x sin ıf the base asphalt in the range of 8.8% to 12.2% at 28 ◦C. At 25 ◦C,ase asphalt was not able to satisfy the specification limit with177.3 kPa but TLPP brought it within the limitation by reducing

1% (w/w) VPP modified asphalt 268.9 622.0 1553.42% (w/w) VPP modified asphalt 303.5 688.9 1828.7

G*x sin ı at 30.0–34.3% level. VPP was also found to improve thefatigue resistance parameter of the base asphalt by 12.7–13.5% at25 ◦C. In literature, PET modified mixture (with dry process) hasbeen determined to have better fatigue life [9].

3.4. Evaluation of Nicholson stripping test results

Incompatible polarity properties of HMA mixture constituents

make stripping more serious pavement problem. Polar aggregateparticles tend to bond with polar water rather than to bond withnon-polar asphalt. Even if the aggregate and asphalt bond eachother strongly, stripping can occur when they exposed to moisture.

M. Gürü et al. / Journal of Hazardous Materials 279 (2014) 302–310 307

Table 5DSR test results.

Asphalt status Test temp. Variables Base asphalt 3% (w/w) TLPPmodified asphalt

5% (w/w) TLPPmodified asphalt

1% (w/w) VPPmodified asphalt

2% (w/w) VPPmodified asphalt

Original (Unaged) 64 ◦C G* (kPa) 1.4195 1.3564 1.1969 1.4337 1.3097ı (◦) 88.07 86.94 86.18 87.93 87.76G*/sin ı (kPa) 1.4203 1.3583 1.1996 1.4346 1.3107

70 ◦C G* (kPa) 0.63931 0.62465 0.57001 0.64879 0.61173ı (◦) 88.85 88.01 87.46 87.33 88.62G*/sin ı (kPa) 0.6394 0.6250 0.5706 0.6495 0.6119

RTFOT residue 64 ◦C G* (kPa) 3.0898 3.0213 3.0292 3.1275 3.0793ı (◦) 86.24 85.79 85.36 85.12 85.81G*/sin ı (kPa) 3.0965 3.0295 3.0392 3.1389 3.0876

70 ◦C G* (kPa) 1.5679 1.3596 1.3538 1.6017 1.3729ı (◦) 87.69 87.23 86.90 87.02 87.25G*/sin ı (kPa) 1.5692 1.3612 1.3558 1.6039 1.3745

PAV residue 28 ◦C G* (kPa) 5206.2 n.d.a 4699.9 4501.2 4732.1ı (◦) 53.47 n.d.a 53.23 54.72 53.75G*x sin ı (kPa) 4183.4 n.d.a 3764.8 3674.5 3816.2

25 ◦C G* (kPa) 8031 5357.3 5297.2 6870.7 6768.4◦ 80

3.1

Sroaat

ı ( ) 50.28 53.G*x sin ı (kPa) 6177.3 432

a Not determined.

everal anti-stripping additives were used to improve the strippingesistance of the asphalt mixtures and successfully outcomes were

btained [13–15,21,22]. In this part of the study, the effects of TLPPnd VPP modifications on the stripping resistance of the asphalt-ggregate mixtures were examined through Nicholson strippingest and the results were presented in Table 6.

800

820

840

860

880

900

920

940

960

980

4.54

Asphalt

Mar

shal

l S

tab

ilit

y (

kg

)..

0% (w/w) TLPP 1%

3% (w/w) TLPP 5%

Fig. 6. Marshall Stability of the

800

840

880

920

960

1000

1040

4 4. 5

Aspha

Mar

shal

l S

tabil

ity (

kg)..

0% (w/w) VPP 1%

3% (w/w) VPP 5%

Fig. 7. Marshall Stability of the

50.05 51.69 52.144060.9 5391.2 5343.7

Basalt aggregate was used in the tests and stripping resistance of60% was observed with the base asphalt. The asphalt mixture was

highly affected by the water as 40% of the total aggregate surfacewas found to be stripped although the aggregate is known to havegood stripping resistance. Stripping resistance was improved sig-nificantly by TLPP and VPP and reached to 95–100%. No stripping

5.55

Content (%)

(w/w) TLPP 2% (w/w) TLPP

(w/w) TLPP 10% (w/w) TLPP

TLPP modified samples.

5 5.5

lt Content (%)

(w/w) VPP 2% (w/w) VPP

(w/w) VPP 10% (w/w) VPP

VPP modified samples.

308 M. Gürü et al. / Journal of Hazardous Materials 279 (2014) 302–310

Fig. 8. FTIR patterns of the base and modified asphalt samples.

Fig. 9. SEM images and EDS analyses of asphalt samples; (a) base asphalt; (b) TLPP modified asphalt; (c) VPP modified asphalt.

M. Gürü et al. / Journal of Hazardous

Table 6Stripping resistances (%).

Additive concentration (%, w/w)

0 1 2 3 5 10

wwrti

3

aafFr

adtoMfw([bTaifp

3

go(wtistccfbpTt

3

icbi0

TLPP 60 70 75 100 95 90VPP 60 95 90 90 95 90

as observed with 3% (w/w) TLPP. Similar results were obtainedith PET additive in literature [12]. The increasing of stripping

esistance with TLPP and VPP implies that the adhesion force athe asphalt-aggregate interface was improved through these mod-fications.

.5. Evaluation of Marshall Test results

Marshall Tests were applied in order to detect the effects of TLPPnd VPP on the stability of asphalt mixtures. Tests were performedt four different asphalt contents from 4% to 5.5%. The test resultsor TLPP and VPP modified asphalts were graphically shown inigs. 6 and 7, respectively as a function of asphalt content used. Eachesult seen in figures was obtained from the average of 3 samples.

PET was seen to lead different variations on the stability ofsphalt mixtures. The replacement of aggregate with PET granulesecreased Marshall Stability [11] while PET modification of mix-ure with dry process resulted to increase the stability dependingn the PET content [7]. In our study, TLPP was found to increase thearshall Stability of the mixtures at low asphalt contents (4–4.5%)

or all concentrations of TLPP, this trend was however reversedhen higher amounts of asphalt were used within the mixtures

5–5.5%) such as the study carried on with PET modified asphalt12]. Although not as effective as TLPP, stability was also increasedy VPP at 4% and 4.5% asphalt contents and the increment, unlikeLPP, was kept on for low VPP concentrations (1% (w/w), 2% (w/w)nd 3% (w/w)) at higher asphalt contents (5% and 5.5%) resulting tomprove the mixture resistance against permanent deformationsor a wide range of asphalt content like the polymers SBS, EVA,olyethylene [23–25] and the polyboron additives [26,27].

.6. Evaluation of FTIR test results

The FTIR patterns of the base and modified asphalt samples wereiven in Fig. 8. As seen in the patterns, the modified samples werebserved to contain different bond structures of the PET additivesTLPP, VPP). The C O bonds which were formed by the additivesere recorded at 1700 cm−1 evidently. This result is consistent with

he fact that esterification takes place with glycolysis reaction exist-ng C O bonds as explained in the preparation of PET additivesubsection. The C C double bond was seen in the FTIR pattern ofhe base asphalt at 1600 cm−1. After the modification process, bondleavage proceeded at 1600 cm−1 for the base asphalt and alkenesonverted to alkanes. So, the C C double bond (at 1600 cm−1) wasound to be rather poor for the modified asphalt samples. The SO2ond at 1300 cm−1, which was not available in the base asphalt FTIRattern, reflected the additive properties to the modified asphalts.he other bond structures were found to be similar with respect tohe FTIR patterns given in Fig. 8.

.7. Evaluation of SEM results

SEM images and EDS results were shown in Fig. 9. When the SEMmages have been examined, it is clear that the removing of volatile

omponents lead to porosity in the samples. The uniformity haseen observed in all the SEM images of the asphalt samples given

n Fig. 9. According to the EDS results, sulphur was determined as.513% for the base asphalt, 3.706% for the TLPP modified asphalt

Materials 279 (2014) 302–310 309

and 2.765% for the VPP modified asphalt. The significant increasein the amount of sulphur in the modified asphalts was supportedby FTIR results.

4. Conclusion

Two novel additive materials, TLPP and VPP, were derived chem-ically from PET bottle wastes and used as additive within the asphaltin this study. The effects of each additive on the asphalt and HMAmixture properties were examined through conventional tests andSuperpave methods. The outcomes were summarized below:

• TLPP and VPP, except for 1% (w/w) VPP, were found to decreasethe viscosity and softening point and increase the penetration ofthe base bitumen. The ductility property was not affected by TLPPwhile decreased by the increase of VPP concentration.

• The low temperature cracking resistance of the base asphalt wasimproved by TLPP and VPP according to the BBR test results show-ing the improved performance of the modified asphalts at lowtemperatures.

• TLPP and VPP modifications, except for 1% (w/w) VPP, reducedthe rutting resistance but both of them were found to offer sig-nificantly improved fatigue cracking resistance based on the DSRtests.

• According to the Nicholson stripping test, TLPP and VPP increasedthe stripping resistance of the asphalt mixture significantly whichimplies that the adhesion force at the aggregate-asphalt interfacewas strengthened through these modifications.

• At low asphalt contents, the mixture stability was found to beimproved by TLPP modification while similar phenomenon wasobtained by low VPP concentrations for a wider range of asphaltcontent resulting to improve the mixture performance againstpermanent deformations.

• TLPP and VPP modified asphalts were produced at 120 ◦C and10 min which allow to reducing the required heat energy andaging of asphalt during modification process with respect to theother polymer based asphalt additives.

Consequently, TLPP and VPP modified asphalts were recom-mended to use in cold and humid regions, in roadway sections withhigh traffic volume and heavy vehicle, in expressways, at bus sta-tions, at curved roadway sections and at roadway junctions in orderto improve the roadway performance. Moreover, the usage of PETwaste as an asphalt modifier in the form of TLPP and VPP can beaccepted as a new practice about the maximization of its end-of-service life management effectiveness beside the recycling and/orenergy recovery processes and will offer not only an alternativebut also a beneficial way of disposal of this ecologically hazardousmaterial.

Acknowledgements

The authors are grateful to Gazi University and Turkish GeneralDirectorate of Highways for the laboratory facilities.

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