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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

AN EXPERIMENTAL STUDY ON EFFECT OF WASTE

TYRE RUBBER ON 60/70 GRADE BITUMEN

Mohammed Sadeque1* and K A Patil1

Bitumen is an important binder used in flexible pavement construction. About 80% of the producedbitumen is used for pavement construction. The quality of the binders can be improved by theirmodification with polymers and rubber obtained from waste tyre. At the same time, utilization ofwaste rubber would solve a serious environmental problem. In the present study effects ofCrumb Rubber (CR) obtained from waste tyre on physical and strength properties of 60/70penetration grade bitumen are evaluated. The crumb rubber modified bitumen is prepared in thelaboratory, taking CR content 2%, 4%, 6%, 8% and 10% by weight of bitumen. It is found that thephysical and strength properties of the binder are improved due to the modification by wastetyre rubber.

1 Civil Engineering Department, Government College of Engineering, Station Road, Aurangabad 43100, Maharashtra, India.

*Corresponding author:Mohammed Sadeque � mdsadeq@rediffmail.com

ISSN 2319 – 6009 www.ijscer.com

Vol. 3, No. 1, February 2014

© 2014 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2014

Research Paper

Keywords: Waste tyre, Modified bitumen, Crumb rubber

INTRODUCTION

Factors such as durability, strength andeconomic need to be consider in design andconstruction of road pavement. To a largeextend these factors are depends on theproperties of binder. Bitumen is recognized asgood adhesives and load resistant materialssuitable for paving applications. The strengthand durability of the bitumen can be increasedby adding small quantity of polymer in it.Polymer, such as styrene–butadiene–styrene(SBS), has been shown to be very effectivemodifier for bitumen due to its thermoplasticelastomeric properties. Uses of SBS

copolymers as bitumen additives are limiteddue to their high cost in comparison tobitumen. Therefore the use of crumb tyrerubber (CR) is an interesting alternative fromboth economical and environmental point ofview. In the present study effect of CR onphysical and Marshall Properties of bitumenhave been studied.

EARLIER STUDIES

Many studies have been carried out on the useof crumb rubber for modification of bitumen.Hak-Seo Kim (2010) claimed that the use ofcrumb rubber as a modifier have positive

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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

effects on rheological properties of thebitumen, including improved penetrationresistance and less potential to permanentdeformation. The creep compliance value forcrumb rubber modified bitumen isconsiderably lower than neat binder. Additionof rubber to the virgin binder increases thecomplex modulus at higher temperatures, andlowered the phase angle at lowertemperatures. Baha Vural Kök et al. (2011)concluded that both SBS and CR modifiedbitumen exhibited reduced temperaturesusceptibility with increasing additive contents.However, this trend was more pronounced forthe SBS modified bitumen. Abdelkadar et al.(1996) based on laboratory investigation onmodification bitumen by pyrolytic carbon blackconcluded that addition of pyrolytic carbonblack in 5 to 30% of weight of the binderchanges the rheological properties of thebinder. The temperature susceptibility of thebitumen is reduced and the loss modulus andthe storage modulus increase significantly at30% pyrolytic carbon black. Also softeningpoint, temperature susceptibility of penetrationand viscosity are also improved by the additionof pyrolytic carbon black.

Praveen Kumar (2009) based on hislaboratory study on rheological properties ofcrumb rubber modified bitumen found that thephysical properties like penetration, ductilityand softening point are improved due to

addition of crumb rubber. It is also found thatcomplex modulus increases with increase inmodifier content but the phase angledecreases with increase in modifier. Theincrease in complex modulus and decreasein phase angle is an indication of higherresistance to deformation as compared tounmodified bitumen. Airey et al. (2002)reported that modified bitumen using crumbrubber showed an improvement in theperformance of pavements over the basebinders as a result of the interaction of crumbrubber with base binders. Due to thisinteraction, the viscosity, physical andrheological properties of the modified bitumenare improved.

MATERIALS AND METHODS

For present study 60/70 penetration gradebitumen, obtained from Shell Corporation Indiais used as base material. The physical andstrength characteristics of the base bitumenare as shown in Table 1.

The rubber used was a sample of reclaimedcar tyres shredded into fine fibers. Apart fromuse as a bitumen modifier, this rubber is alsoused for playground surfaces and athletictracks, carpet backing, brake pads, roofingand cattle mats. The sample used was derivedfrom ambient grind of waste tyres. Table 2contains typical constituent of crumb rubber as

indication of content only.

Table 1: Properties of Base Bitumen

Properties Penetration Value Softening Point Ductility Stability Flow

Values 67 (dmm) 40 (ºC) >120 (cm) 16.38kN 3.05mm

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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

Experimentation

The crumb rubber modified bitumen isprepared in the laboratory by heating bitumenup to 200oC and shredded waste tyres aremixed and stirred for 1 h. The waste rubber ismelted and blended in the bitumen. The wastetyre modified bitumen is prepared for 2%, 4%,6%, 8% and 10% of waste tyre by weight ofbitumen. The various physical and mechanicalproperties like penetration, softening point andductility of these modified bitumen aredetermined and compared with neat bitumen.The penetration test is carried out by standardbitumen penetration test apparatus, measuredin terms of 1/10th of mm under weight of 100 gfor 5 s at 25oC. The softening point isdetermined by ring and ball method. Theductility is determined in terms of centimeterat 27oC. Also the Marshall Stability and flow ofneat and modified bitumen is determined. The

aggregate grading taken for the MarshallStability test is as shown in the Table 3 andgradation curve is as shown in Figure 1.

Table 2: Typical Constituentsof Crumb Rubber

Material Content (%)

Natural rubber 25-50

SBR/Butadiene content 5-30

Carbon black 25-30

Processing agents 20-25

Acetone extraction 3.5-9

Ash content 10

Benzene Extraction 4-6

Table 3: Aggregate Grading for Marshall Test

Size (mm) 10.0 4.75 2.36 0.6 0.3 0.15 0.075 Bitumen

Cumulative Percentage 80-100 55-75 35-50 18-29 13-23 8-16 4-10 5%

Figure 1: Gradation Curve of anAggregate Blend for Marshall Test

RESULTS AND DISCUSSION

The penetration test results are as shown inFigure 2. It is observed that penetration valueis reducing with increase in concentration ofCR. This is an indication of increase in stiffnessand shear strength of binder. The penetrationvalue of neat bitumen reduces from 67 dmmto 46 dmm at 10% of CR content. Absorptionof maltene phase by CR increases theasphaltene part of bitumen. Furthermore, thestiffness of CR particles is more than bitumen.Hence, increasing the CR content leads toincreased stiffness.

The effect of crumb rubber on softening pointof bitumen is shown in the Figure 2. The

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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

Figure 2: Effect of CR Concentrationon Penetration of Bitumen

softening point refers to the temperature atwhich the bitumen attains a particular degreeof softening. The use of crumb rubber inbitumen modification leads to an increasein the softening point and viscosity ascrumb rubber content increases Effect of CRon softening point of bitumen is shown inFigure 3. It is found that the softening point ofbitumen is increasing with increase in the CRcontent. The softening point increases from40oC to 56.5oC at 10% of CR content. Crumbrubber absorbs the light oily components ofbitumen in CR-bitumen matrix, which reducesthe content of free radicals. Antioxidant andanti-ozone agent in CR raised the anti-oxidative capacity of Crumb Rubber ModifiedBitumen (CRMB). These two reasonscontribute directly to the improvement of anti-oxidative capacity of CRMB which leads tohigher softening point (Fereidoon et al., 2012).

However, the ductility of the bitumenreduces with increase in the CR percentagein bitumen as represented in Figure 4. The

Figure 3: Effect of CR Concentrationon Softening Point of Bitumen

reduction of oily material in CR-bitumen mixand presence of CR particles in specimenwhich have no deformation properties resultsin reduction of ductility (Fereidoon et al.,2012).

The effect of CR modification on the stabilityand flow value, on the basis of Marshall testare as shown in the Figure 5 and 6 respectively.It is found that the stability value increasing with

Figure 4: Effect of CR Concentrationon Ductility of Bitumen

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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

increasing in CR content; however theflow remains fairly unchanged. This impliesthat the stiffness and deformation property ofthe bituminous concrete is improvingwith increase in CR content. The stability valueof neat bitumen mix increases from 16.38 kNto 28.53 kN for bitumen modified by 10% ofCR.

CONCLUSION

Based on laboratory investigations andobtained results in this study, the followingconclusions can be drawn.

1. The use of crumb rubber as a modifierseems to have positive effects on physicaland strength properties of the binders,including improved penetration, softeningpoint.

2. There is a significant improvement in thestability value of bituminous concrete.However the ductility of the binder reduceswith increase in CR content. It is thereforerecommended to use the 5% to 10% of CRto keep the ductility with in permissible limit.

3. The use of crumb rubber as an additive inbitumen modification would reduce pollutionproblems and protect our environment aswell.

REFERENCES

1. Abdelkader Chaala, Christian Roy andAbdellatif Ait-Kadi (1996), “RheologicalProperties of Bitumen Modified WithPyrolytic Carbon Black”, Fuel, Vol. 75,No. 13, pp. 1575-1583.

2. Airey G D, Singleton T M and Collop A C(2002), “Properties of Polymer ModifiedBitumen after Rubber-BitumenInteraction”, journal of materials in civilengineering, pp. 344-364.

3. Baha Vural Kök and Hakan Çolak (2011),“Laboratory Comparison of The Crumb-Rubber and SBS Modified Bitumen andHot Mix Asphalt”, Construction andBuilding Materials, Vol. 25, pp. 3204-3212.

Figure 5: Effect of CR Concentrationon Stability of Bitumen Mix

Figure 6: Effect of CR Concentrationon Flow of Bitumen Mix

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Int. J. Struct. & Civil Engg. Res. 2014 Mohammed Sadeque and K A Patil, 2014

4. Fereidoon Moghadas Nejad, PedramAghajani, Amir Modarres and HasanFiroozifar (2012), “Investigating TheProperties of Crumb Rubber ModifiedBitumen Using Classic and SHRPTesting Methods”, Construction andBuilding Materials, Vol. 26, pp. 481-489.

5. Hak-Seo Kim, Soon-Jae Lee and SerjiAmirkhanian (2010), “Rheological

Investigation of Rubber Modified AsphaltBinders”, KSCE Journal of CivilEngineering, Vol. 14, No. 6, pp. 839-843.

6. Praveen Kumar H C, Mehndiratta K andLakshaman Singh (2009), “RheologicalProperties of Crumb Rubber ModifiedBitumen-A Lab Study”, Journal ofScientific and Industrial Research, Vol.68, September, pp. 812-816.