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186 J SCI IND RES VOL 72 MARCH 2013Journal of Scientific & Industrial ResearchVol. 72, March 2013, pp. 186-192

*Author for correspondence

E-mail: [email protected]

Laboratory performance of stone matrix asphalt containing composite

of fly ash and plastic waste

Umadevi Rongalia, Gagandeep Singhb, Anita Chourasiyacand P.K. Jaind

CSIR-Central Road Research Institute, New Delhi-110025, India

Received 11 May 2012; revised 06 November 2012; accepted 03 January 2013

In this paper, the optimum composition of fly ash and plastic waste in a composite has been established based on various

performance tests. The optimum dose of plastic waste in composite is 8% weight of fly ash. Laboratory tests indicated increased

resistance to moisture damage in stone Matrix Asphalt (SMA) mixture containing composite as filler. The values of resilient

modulus of the SMA mixture containing composite are fairly high compared to SMA mixture containing lime as filler. The rutting

in SMA mixture containing composite is reduced to one third as compared to conventional SMA mixture without composite. The

results of mechanistic analysis indicate that there is an increase in allowable number of traffic on modification of SMA with

fly ash plastic waste composite as filler in place of lime.

Keywords:Stone Matrix Asphalt, Fly Ash, Plastic waste, Composite, Resilient Modulus, Rutting.

Introduction

Stone Matrix Asphalt (SMA) is a gap graded mixture

that maximizes the coarse aggregate content to the tuneof 70-80% in the mixture to ensure stable stone-on-stone

contact1-8. The requirement of filler in SMA mixture isof the order of 10-12 percent and binder content is high

(more than 6 %), so that to form mortar in voids of SMA

structure and achieve better durability. Cellulose fiber is

added to prevent drain down of the binder at highoperating temperatures. The increase of contact pointsin aggregate matrix of SMA mixture produce high

resistance to rutting in bituminous surface. IRC: SP: 79-

2008 specify requirements of design and construction ofbituminous surface using SMA mixture9. The sources of

good quality mineral aggregate and traditional filler likelime are depleting due to large scale development of road

infrastructure. Therefore, a need is felt to explore

alternate materials for conservation of available mineralmaterials. Highway sector has potential to utilize

sufficient quantity of waste materials10, if their effect on

performance of pavement proves to be technically,economically and environmentally acceptable and meet

the requirement of standards and specifications. Presently,about 100 thermal power plants operating in India are

producing over 170 million tones of fly ash every year,

which is dumped in the land adjoining to thermal power

plants, adversely affecting nearby environment besidesconsuming useful land. Nearly, 65,000 acre of land isoccupied by ash ponds in the country. It is estimated that

production of ash will reach to 600 million tons in 203010.Fly Ash (FA) and Plastic Waste (PW) are two abundantlyavailable waste materials with several good

characteristics, which make them suitable for bituminousroad construction10-18. Incorporation of 10% fly ash asfiller is reported by researchers14. Some studies also

reported significant improvement in fatigue life of mixesupon addition of fly ash17. Particle size of fly ash has

been found to make significant effect on viscosity of fly

ash and bitumen blend. The viscosity values of finerblends are observed higher. Better performance in termsof resistance to rut depth, tensile strength and fatigue

life26 .Use of fly ash as filler also leads to reduction inrolling temperature and thus consumption of lesserenergy27.

Use of plastic waste in bituminous mixes has been

found acceptable on the basis of several studies19-25

. Thebituminous mix containing 8% waste polymer modifier(WPM) leads to considerable improvement in propertiesof mix20. Regarding availability of plastic waste, the per

capita consumption of solid plastic in developing countrieslike India is 10kg in a year. Solid plastic litter generatedfrom plastic goods is non bio-degradable 1 9 . Since

requirement and other pertinent physical properties offly ash and fly ash plastic waste composite as filler for

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187RONGALI et al: LABORATORY PERFORMANCE OF STONE MATRIX ASPHALT

bituminous mixture are acceptable and SMA mixtureconsume 10-12% filler by weight of total mineral

aggregate, a study was undertaken to explore use of

alternate filler materials such as fly ash and its compositewith plastic waste as a substitute of traditional filler lime.

In view of above cited literature and associated problemsfor disposal of fly ash and plastic waste, a study on use

of these solid waste materials in roads construction wastaken up. The main objectives of this study were to

evaluate mechanistic properties addressing performance

of fly ash plastic waste composite with differentcompositions as alternate to conventional lime filler in

bituminous road construction.

Experimental DetailsMaterialsPlastic waste in the shredded form (2-8 mm) was

used in this study. The Thermo Gravimetric Analysis(TGA) and Differential Scanning Calorimeter (DSC)

study of plastic waste indicated initial decompositiontemperature as 399C. The melting temperature was

observed in the range of 124-129C from DSC analysis

Fly ash used in this study was obtained from NTPC Ltd.Dadri, (U.P). To check the suitability of fly ash various

tests were performed on fly ash such as bulkdensity(IS:2386 Part 1),specific gravity(IS:2386 Part 1),

water absorption(IS:2386 Part 3), finenessmodulus(IS:2720 Part 4), methylene blue(IS:2720 Part 26)and plasticity index tests(IS:2720 Part 6) and values

obtained were 1.21, 2.1, 1.59, 2.44, 0.59 and non plasticrespectively.

Bitumen

VG-30 grade paving bitumen from Mathura refinery

conforming to IS: 73-2006 was used. Various physical

properties of bitumen were found such as penetrationvalue, softening point, ductility, specific gravity, viscosity

at 60C and 150C as per IS: 1201 to 1210. The values

obtained are 61, 47, 75+, 1.01, 2449 and 360 respectively.

Aggregate

The mineral aggregate (granite) was obtained from

the local quarry and various physical properties wereobtained, as per IS:2386 to check the quality such as

aggregate impact value (11.23), water absorption test(0.85%), specific gravity (2.63), combined (elongation

and flakiness) index (29.5%) and stripping (99%).

Mixture design method

In the present study, three different SMA mixtureswere designed and made according to IRC SP: 79-2008

standards. The aggregates were blended to obtain the

values of grading as specified in IRC: SP-79-20099. Threedifferent mixes, controlled SMA (with lime filler), SMA

containing fly-ash and SMA containing fly ash- plasticwaste composite were made and are designated as SMA

1, SMA 2 and SMA 3 respectively. Effect of plastic waste

on VCA and air voids is shown in Figure 1.

Specimen preparation

Fly ash was coated by pre decided quantity of plastic

waste at different dosage level. The design of optimumbitumen content was done by standard Marshall Method

(ASTMD: 1559). Specimens of mixes were prepared

by heating aggregates at 150 C. The fly ash pre coatedwith plastic waste in requisite quantity was then added

and mixed thoroughly in a mixing pan followed by additionof melted bitumen at 164 C. Ingredients were then mixed

thoroughly and poured in Marshall mould assembly at

150 C. Samples were prepared using Marshall Method

Fig. 1Effect of plastic waste on VCA and air voids of SMA mixture containing fly ash

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188 J SCI IND RES VOL 72 MARCH 2013

50 blows on both faces. The properties of designed SMA

mixtures are given in Table 1.

Test procedures

I ndi rect tensile strength (ITS) test

Indirect tensile strength test is significant to evaluate

resistance of compacted bituminous mixture to crackingas well as sensitivity of mixture to moisture damage. To

identify whether the coating of bitumen binder and

aggregate is susceptible to moisture damage, TensileStrength Ratio (TSR) is determined according to

AASHTO T 283, Results of indirect tensile strength andTSR are plotted in Figure 2 and Figure 3.

Resistance to deformation

The aspect of deformation at high temperature has

been investigated by conducting rutting test. Rutting isan important parameter for design of a SMA mixture.

To check the rutting resistance of the mixture, test wasperformed by Wheel Tracking Device (WTD). The

WTD is destructive test and it involves direct contact

between the loaded wheel and the rectangular test

specimens. The test was conducted on the prepared slab

specimen of 300X300X50 mm at optimum binder contentcontaining lime, fly ash and fly ash - plastic waste

composite as filler. The test was conducted as per BS:598-1998. The total numbers of 20,000 passes were

applied at 45 C and resulting rut depth was measured.

The data of rut depth of different mixes are plotted inFigure 4.

Table 1Properties of designed SMA mixture

Properties Requirements SMA1 SMA 2 SMA 3

Bitumen content, % 5.8 min 6.0 6.2 6.0

Stabilizing additive, % Min 0.3%, 0.3 0.3 0.3

Air void content, % 4 4.4 4.1 4.3

Void in mineral aggregate, % 17min 17.0 17.5 18.8

Compactive effort, No of blows 50 50 50 50

Drain down, %

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Resil ient modulus (MR) test

To check the effect of fly ash and plastic waste and

their composite with different composition on the resilient

modulus values, the repeated loading indirect tensile teston compacted bituminous mixtures was performed as

per ASTM D-4123. The test was conducted by applyingthe compressive load in the form of haversine wave at

25, 30, 35, 40 and 45 C for controlled SMA mixture

(SMA 1), SMA with fly ash filler (SMA 2) and SMAwith fly ash plastic waste composite filler (SMA 3).

The specimens were conditioned for 24 h in theenvironmental chamber at the given temperature and then

subjected to repeated loading pulse width of 100 ms, and

pulse repetition period of 1000 ms the results are plottedin Figure 5.

Mechanistic anal ysisKENPAVE software is used to calculate the tensile

strain at the bottom of bituminous layer and thecompressive strain at the top of the sub grade layer. These

values are used in the fatigue and rutting model to

estimate the pavement life and the benefits are presentedin the form of Traffic Benefit Ratio (TBR) [34]. In this

study, 8 tonne axle load having two sets of dual tireswith 800 kPa tire pressure and 30 cm dual spacing is

taken as input for the analysis. Based upon test result

values of resilient modulus, mechanistic analysis of three

layer structure with 10 cm of SMA layer as top layer

and 40 cm aggregate layer having resilient modulus value

of 200 MPa and sub grade having CBR of 8% isanalyzed. Results are presented in Table 2.

Discussion of test resultsProperties of ingredients

Result of test performed on different ingredients of

SMA mixture indicates that fly ash used in this study is

non plastic. A lower value of methylene blue shows fewer

amounts of clay and organic material in fly ash. The fly

ash used as filler meet MoRTH requirements.

Classification tests on bitumen were performed and

results of test are given earlier. Test data indicate that

bitumen used in this study can be graded as VG-30. The

particle size of shredded plastic is in the range of 2-8

mm, which lies in conformity of findings reported earlier 19.

The TGA test indicates that decomposition of plastic

waste does not occur below 399 C, indicating its safer

use in bituminous construction. The melting, behavior is

important parameter from mixing point of view. From

DSC analysis the melting range of 124C - 129C of

Table 2Mechanistic analysis of three layered structure

Composition Tensile strains at bottom of Compressive strains on TBR

bituminous layer () top of sub grade()SMA with lime filler 448 520 -

SMA with fly ash 461 524 0.96

SMA with 5% plastic waste by weight 319 469 1.65

of fly ash

SMA with 8% plastic waste by weight 313 466 1.70

of fly ash

Fig. 5Effect of plastic waste on resilient modulus value of SMA mixture containing fly ash and different dosage of plastic waste

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plastic waste is favorable for preparation of mix at 140to 160 C. The endothermic peaks in DSC curves around

260 C indicate initiation of decomposition process.

Design of SMA mi xes

It can be seen from the data given in Table 1 that

the optimum bitumen content is in the range of 6.0 to 6.2

% by weight of aggregate and also meet requirements

described in IRC: SP: 79-2008. It can be seen from thedata that VCA mix values of all the SMA mixtures are

less than/equal to VCADRC

and VMA are more than

specified value of 17 %. Therefore, designed SMA

mixtures are having fairly good stone-on-stone contact

to control rutting in mixture.Figure 1 show effects of

plastic waste on VCA and air voids in the compacted

mixture. There is increase in air voids and VCA, if plastic

waste content is exceed 8% by weight of ash.

Drain down studies

Preventionof draining of bitumen in SMA mixtureduring transportation is an important parameter. It can

be seen from the data given in Table 1 that fly ash as

well as fly ash plastic waste composite as filler in place

of lime reduce draining tendency of binder from mixture.

Moisture sensiti vity studi es

TSR is widely acceptable test to address damage

caused by the ingress of moisture. The TSR value of

traditional SMA with lime as filler (SMA 1) is 86%, which

is in conformity to IRC standard. The values of TSR of

SMA containing fly ash (SMA 2) and fly ash plastic waste

composite(SMA 3) are recorded 92 and 93%, which are

7-8% higher than traditional SMA mixture (SMA 1),

indicating better resistance to moisture damage.

Therefore, SMA mixes containing fly ash and composite

of fly ash plastic waste as fillers may be used in

locations of higher rainfall. Results plotted in Figures 2

and 3 further indicate that highest value of indirect tensile

strength and TSR are observed using a composite

containing 5 to 8 % plastic waste in fly ash plasticwaste composite, used as filler in SMA mixture.

Resil ient modulus Test, MR

Resilient modulus is the most important variable formechanistic design of flexible pavement structure. It is

the measure of pavement response in forms of dynamic

stress and corresponding strains. Figure 5, show the

obtained MRvalues. The data plotted in Figure 5 indicatethat plastic waste modification has improved the resilient

modulus of the modified mixes as compared to traditional

SMA mixture containing lime as filler for all the test

temperatures. The average resilient modulus of traditional

mixture at 35C was found to be 3503 MPa for the

mixture containing 8% plastic waste by weight of added

fly ash in SMA mixture. However, MR

values without

plastic waste containing 10% fly ash at 35 C is observed

1331 MPa in comparison to 1431 MPa of SMA mixture

containing lime as filler. The average resilient modulus

values at 45 C increased from 409 MPa to 1407 MPaupon addition of 8% plastic waste in fly ash which is

quite high. The addition of 2 to 10 % plastic waste in fly

ash resulted progressive increase in MRvalue from 1331

MPa at 2% PW to 3503 MPa at 8% PW. The value of

MRat 5% plastic waste is 2951 MPa at 35 C compared

to 1431 MPa of traditional SMA mixture. Values of MR

at 45C are very high and support to rutting behavior of

their mixtures, when tested by wheel tracking test at

same temperature. The pozzolanic properties of fly ash

together with elastic properties of plastic waste

contributed to high values of MRat 35 and 45 C, resultingto overall performance.

Rutting studiesRutting is key factor for design and evaluation of the

performance of SMA mixtures. It can be seen from Figure4 that observed rut depth values of SMA mixtures are in

the range of 1 to 5 mm using VG 30 bitumen binder and

lime, fly ash/fly ash plastic waste composite as filler.

Table 3Rutting in SMA mixtures

Composition of Composite Rutting in mm for different cycle range

0 - 5000 5000 -10000 10000 - 20000

A. 10% Fly Ash (SMA 2) 1.79 2.04 2.29

B. Fly Ash+ Plastic Waste (5%)(SMA 3A) 1.57 1.79 2.01

C. Fly Ash+ Plastic Waste (10%) (SMA 3B) 0.64 0.77 1.09

D. SMA with Lime (SMA 1) 3.48 4.09 4.71

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Data plotted in Figure 6 indicate that higher resistanceto rutting is observed when fly ash is used. However,lesser rut depth values of SMA mixtures is attributed tohigher percentage of coarse aggregates and developmentof stone on stone contact in the matrix. Data given inTable 3 indicates that SMA mixture containing fly ash

plastic waste as filler, rut depth in mixture specimen isfurther reduced to about 1 mm which is attributed to

higher value of resilient modulus at 45 C. Data given inTable 4 indicates that rate of rutting is highest during 0-5000 cycles for SMA mixture containing lime as filler ascompared to SMA 2 and SMA 3 containing fly ash. Therate of rutting is lowest (Table 4) for SMA mixture

containing filler of composite and presented in Figure 6.

Mechanistic analysis of data

The results of mechanistic analysis of three layeredstructure are presented in Table 5. It can be seen that

the modification of SMA with only fly ash leads toincrease in the tensile strains at the bottom of the SMAlayer from 448.2 to 461.8 but modification of SMAwith fly ash and plastic waste show the positive resultswith the decrease in tensile strain to 318.9 and 313.3 in case of 5% and 8% dosage level of waste plastic ascompare to unmodified SMA. The compressive strainon the top of sub grade also reduces for SMA modified

with fly ash and waste plastic as compare to unmodified

SMA and SMA modified with fly ash only. The

compressive strain falls from 519.7 to 468.8 and 466.2 on modification with 5% and 8% dosage level of waste

plastic respectively and giving the TBR of 1.65 and 1.70.These reductions in the strain values are due to increase

in the resilient modulus values of SMA when modified

with the fly ash and plastic waste composite.

Conclusions and RecommendationsThis study has been done for the performance of

Asphalt with fly ash and the following conclusions are

drawn:

Fly ash can be used as filler in place of traditionallime in Stone Matrix Asphalt.

Properties of fly ash as well as SMA can be

improved by coating fly ash with plastic waste.

The optimum content of plastic waste in

composite is 8% by weight of fly ash. Incorporation of plastic waste in excess of 8%

led to increase in VMA and air voids in compactedmixture.

Plastic waste in fly ash led to increase in values

of indirect tensile strength to resist cracking.

Incorporation of plastic waste in fly ash enhances

values of MRat 35 C and 45 C.

Table 4Rate of rutting in SMA mixture

Composition of Composite Rate of rutting per 1000 cycles

0 - 5000 5000- 10000 10000 -20000A. 10% Fly Ash (SMA 2) 0.358 0.050 0.025

B. Fly Ash + Plastic Waste (5%) (SMA3A) 0.314 0.044 0.022

C. Fly Ash + Plastic Waste (10%)(SMA 3B) 0.130 0.026 0.013

D. SMA with Lime (SMA 1) 0.690 0.034 0.062

Fig. 6Rate of Rutting in different SMA mixture.

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Mechanistic analysis of three layered structure

indicate TBR in the range of 1.65 to 1.70.

Plastic waste reduces rutting in SMA mixture

considerably.

SMA containing composite can be used as

wearing surface and bituminous base coursesubjected to heavy traffic for flexible pavements.

AcknowledgementsSincere thanks are due to Dr. S. Gangopadhyaya

Director CSIR-Central Road Research Institute, NewDelhi 110025 for permission to publish this paper.

Thanks are due to Dr. Divesh Tiwari for the assistance

during testing of mechanistic properties.

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