Waste Tyre Rubber in Asphalt Pavement Modification

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/263277401 Waste Tyre Rubber in Asphalt Pavement Modification. Article in Material Research Innovations · April 2014 Impact Factor: 0.83 · DOI: 10.1179/1432891714Z.000000000922 CITATIONS READS 2 60 2 authors, including: Nuha Mashaan University of Malaya 33 PUBLICATIONS 76 CITATIONS SEE PROFILE Available from: Nuha Mashaan Retrieved on: 16 May 2016 YOUR ARTICLE Please review the proof* of your article carefully, checking for any final typographical errors or minor necessary updates. Please address and answer in full any queries which the copyeditor may have raised on the Author Query sheet accompanying your proofs. Please make clear any necessary corrections, within 3 working days, using one of the following methods: ƒ Use Adobe's Comments and/or Editing Tools to indicate changes directly onto the PDF and return via email. Please request guidelines if required. ƒ Email the necessary corrections as a list citing the page and line number where a correction needs to be made, how the text currently appears, and what it should be changed to. ƒ Use the BSI proof marks to indicate changes on a paper printout of the PDF and email, fax or post the pages (contact details below). Production Editor, MRI Maney Publishing, 1 Carlton House Terrace, London, SW1Y 5AF, UK Tel.: +44 (0) 20 7451 7369 Fax: +44 (0) 20 7451 7307 mri@maneypublishing.com VIEWING YOUR ARTICLE’S PRODUCTION STATUS AND PLACING ORDERS USING MANEYTRACK http://maneytrack.maney.co.uk Approximately three weeks ago, you will have received an email detailing your log-in details for Maney Publishing’s web-based production tracking system, ManeyTrack. Via ManeyTrack you can: - View the production status of your article at any time. - Place orders for, offprints or to make your article open access. Please log in using the web address, above. If you have misplaced your log-in details please check your spam/junk folder. If you are still unable to find them please click on the above url and click on ‘Forgot Password’ and follow instructions. If you require further technical assistance, please contact the Administrator: ManeyTrackAdmin@maneypublishing.com ADDITIONAL INFORMATION This journal is hosted online at www.maneyonline.com/mri OFFPRINTS: You will receive a complimentary PDF eprint of your final article. If you wish to purchase traditional hardcopy offprints please log in to ManeyTrack to view prices and to place your order – see details for ManeyTrack above. GET FOUND, GET READ, GET CITED As part of our commitment to making the content we publish as visible as possible, Maney offers its authors use of the Kudos service which is designed to help you increase article readership and citations by enabling you to explain, enrich and share your articles. Corresponding authors will receive a registration email regarding the service once the article is published. To find out more visit www.growkudos.com. FEEDBACK Tell us about your publishing experience at: https://www.surveymonkey.com/s/stm_authorsurvey *Please note this PDF file may not be offered for commercial sale or for any systematic external distribution by a third party. Kind regards, Production Editor Waste tyre rubber in asphalt pavement modification Nuha Salim Mashaan* and Mohamed Rehan Karim Currently, a serious problem that leads to environmental pollution is the abundance and increase of waste tyres from vehicles. The major approach to solve this issue is to recycle waste tyre rubber including its use as crumb rubber modifier in asphalt pavement. This study aims to investigate the effect of crumb rubber modifier on engineering properties of rubberised asphalt. The physical and rheological properties of rubberised asphalt binder that include different percentages of crumb rubber modifier (0, 4, 8, 12, 16 and 20%) were determined and assessed using various laboratory tests. Results showed that 16% crumb rubber modifier at 180°C blending temperature have a significant effect on modified binder engineering properties. Also, the study promotes the recycle of waste tyre rubber in an environment friendly manner. Keywords: Waste tyre rubber, Bitumen, Rubberised bitumen, Physical properties, Rheology, Environmental impact Introduction Scrap tyres lead to serious disposal problems. However, the use of scrap tyres in asphalt pavements in the form of fillers/additives could minimise the environmental pollution and maximise natural resource conservation. There are two major approaches: first to resolve the wastage of rubber and disposal of scrap tyres which are to reuse waste rubber, second to reclaim raw resource of rubber. Crumb rubber is made by shredding scrap tyre into a particular material free of fibre and steel. There are two techniques to produce crumb rubber: ambient grinding and the cryogenic process.1 Ambient grinding process can be divided into two methods: granulation and cracker mills. Ambient describes the temperature when the waste tyres rubber as its size is reduced. The material is loaded inside the crack mill or granulator at ambient temperature. Cryogenic tire grinding consists of freezing the scrap tire rubber using liquid nitrogen until it becomes brittle, and then cracking the frozen rubber into smaller particles with a hammer mill. Cryogenic grinding is a cleaner, slightly faster operation resulting in production of fine mesh size. The high cost of this process is a disadvantage due to the added cost of liquid nitrogen. Malaysia’s production of scrap tyres is about 10 million pieces per annum and unfortunately they are being disposed in an environmentally unfriendly manner.2 A bitumen 80/100 penetration grade is commonly used in Malaysia and due to high traffic loading and hot weather conditions, pavement distresses appear quite early in the service life of the asphalt pavement. Thus, Center for Transportation Research, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia *Corresponding author, email nuhaasim@siswa.um.edu.my © W. S. Maney & Son Ltd 2014 DOI 10.1179/1432891714Z.000000000922 the use of crumb rubber in bitumen modification is considered as a sustainable technology which would transform the conventional asphalt into a new asphalt mixture highly resistant to rutting and fatigue deformations. Since the 1960s, the use of rubberised bitumen binder in road materials applications has gained increased interest in the paving industry. Hence, the task of current asphalt researchers and engineers is to look for different kinds of modified bitumen with rheological properties that would directly affect and improve the asphalt pavement performance. Currently, researches on applications of rubberised bitumen binders have reported many advantages. These advantages include improved bitumen resistance to rutting due to high viscosity, softening point, improved bitumen resistance to surface-initiated cracks and reduction of fatigue cracking, reduction of temperature susceptibility and improved durability as well as reduction in road pavement maintenance costs.3–6 The properties of rubberised bitumen binders at a wide range of temperatures are highly dependent on the chemistry of the bitumen binder, the crumb rubber content, size and texture of rubber particle and the blending conditions.3–7 The viscous-elastic properties of bitumen are determined by the differing percentages between asphaltenes and maltenes fraction. According to the microstructure and the colloidal system of bitumen, asphaltenes are diffused into an oily matrix of maltenes, and encased by a shell of resins whereby its thickness varies with the temperature that is being tested.8,9 Thus, the mechanical properties and microstructure of bitumen are dependent on bitumen composition, blending temperatures and on the degree of aromatisation of the maltenes and the concentration of asphaltenes.9 Previous research has shown that the major mechanism of the bitumen–rubber interaction is the swelling of the Materials Research Innovations 2014 VOL 18 SUPPL 6 S6-1 Mashaan and Karim Waste tyre rubber in asphalt pavement modification 1 Continuous blend asphalt rubber produced at laboratory10 rubber particles because of the absorption of the light fractions oil into the rubber particles and stiffening of the residual binder.5,6 Also, the improved property of rubberised bitumen is likely to depend on interaction between crumb rubber and bitumen binder. Crumb rubber particles swell when mixed with the bitumen binder to form a viscous gel; leading to an increase in the viscosity of the rubberised bitumen binder.3 The aim of this research was to determine the effects of incorporating crumb rubber modifier (CRM) on the engineering properties of modified bitumen binder. The physical and rheological properties of bitumen binders that is modified using various percentages of CRM were determined and assessed with laboratory tests. Experimental programme Materials The bitumen binder used in this study was 80/100 penetration grade, obtained from Shell supplier located in Kuala Lumpur, Malaysia. In this study, fine crumb rubber size # 30 (0·6 mm) was selected in order to reduce segregation. Sample preparation Rubberised bitumen binder was prepared by mixing bitumen 80/100 penetration grade with CRM (0, 4, 8, 12, 16 and 20% by binder weight) passing the 30-mesh sieve. The propeller mixer is used to mix the bitumen and the crumb rubber at two different blending temperatures of 160 and 180°C for 90 minutes continuous blending. Binder mixing was conducted at the velocity speed of 350 rev min−1. The fabrication of rubberised bitumen samples as shown in Fig. 1. Results and discussion Penetration test results Figure 2 illustrates the penetration value versus (CRM) content and blending temperature. The penetration value of the CRM-modified binder for different blending temperatures depends on their relation with crumb rubber content. It shows a decrease in penetration as the rubber content increased in the bituminous specimens. It is appears that the decrease in penetration of CRM modified binder samples compared with unmodified binder was approximately about 17–80% for 4 and 20% rubber content, respectively. The results showed that the CRM rubber content in the mixture led to lower penetration values, agreeing with findings of previous studies. These results are due to the crumb rubber content exhibiting a strong effect on penetration reduction by increasing the stiffness of crumb rubber modified bitumen binder. This would make the binder more resistant to high temperature susceptibility, thus leading to high resistance to permanent deformation like rutting.11 Additionally, the increase in blending temperature enhanced the particle size of the rubber and led to the increase in rubber mass through the interaction and swelling of the rubber into the bitumen during the blending process, which led to the decrease in the penetration values of rubberised bitumen samples. Softening point test results Figure 3 shows the softening point value versus (CRM) content and blending temperature. As displayed in Fig. 5, at 160°C the increase in CRM content led to high softening point of modified bitumen samples by about 1–10°C for 4 and 20% rubber content, respectively, while the softening point showed more increase at the Binder tests A series of binder tests were carried out on the modified binder for purpose of selecting the optimum combination parameters of mixing temperature and CRM content. The binder tests include Brookfield viscosity at 135°C (ASTM D4402), penetration test (ASTM D5-2002) softening point test at 25°C (ASTM D 36) and dynamic shear rheometer (DSR) at 76°C (ASTMD-4 proposal P246). This proposal test method focuses on determining the linear visco-elastic properties of bitumen when tested in dynamic (oscillatory) shear using parallel plate test geometry. Specification testing of DSR was performed at a test frequency of 10 rad s−1. S6-2 Materials Research Innovations 2014 VOL 18 SUPPL 6 2 Illustrates the penetration value versus (CRM) content and blending temperature Mashaan and Karim Waste tyre rubber in asphalt pavement modification 3 Shows the results softening point of rubberised bitumen 5 Complex shear modulus results at 76°C blending temperature of 180°C by about 2·5 to 15·5°C for 4 and 20% crumb rubber content, respectively. The increase of rubber content in the mix might be related to an increase in the asphaltenes/resins ratio which enhanced the stiffened property and make the modified binder less susceptible to temperature changes. Also, the increase in blending temperature led to the increase in rubber volume through the interaction and swelling of the rubber into the bitumen during the blending process, thus, leading to the an increase in the softening point values of rubberised bitumen samples. This increase in softening point was similar with the findings of Bahia and Davis.12 The main factor in the increase in softening point can be attributed to crumb rubber content, regardless of type and size. The increase in softening point led to a stiff binder that has the ability to enhance its recovery after elastic deformation. Moreover, this increase in softening point might have resulted from the increase in binder molecular weight when the crumb rubber interacted with the bitumen binder. is highly important to select the temperature at which the binder would maintain an acceptable viscosity that enables the bitumen binder to coat the aggregate effectively. This, in turn, would help to ensure better workability of rubberised bitumen, which reduce the permanent deformations. The increase in viscosity might be due to the amount of asphaltenes in the bitumen that enhanced the viscous flow of the modified bitumen sample during the interaction process. In general, higher crumb rubber content was found to lead to an increase in the viscosity at 135°C.3 According to the Asphalt Institute, the specification of a maximum viscosity at 135°C should not be more than 3 Pas for unaged binder. Thus, the viscosity of 20% rubber content at different blending temperatures has exceeded the limit and thus, it is not recommended.14 Dynamic shear test results Complex shear modulus G* result Viscosity refers to the fluid property of the bitumen and it is a gauge of flow-resistance. At the application temperature, viscosity greatly influences the potential of the resulting paving mixes. The increase in viscosity due to varied blending temperature and different CRM content showed significant effect for all modified samples for mixing time of 90 minutes as shown in Fig. 4. The increase in viscosity with increased blending temperature and crumb rubber content has been verified by Bahia and Davies,13 and Lee et al.14 Based on the viscosity results of this study, its increase was accompanied by the increase in rubber content from 4% to a high CRM content of 20% by binder weight. Moreover, the increase in viscosity might be due to CRM content with higher blending temperature, which would increase the elasticity and break down the crosslink of rubber; these aspects would make the modified binder thicker and more elastic. In addition, during sample preparation it As displayed in Fig. 5, an increase in CRM content and blending temperature leads to an increase in the complex shear modulus G* at 76°C. The results showed that G* appears to increased as the crumb rubber content increases. In this study, adding crumb rubber to the base bitumen increased the complex shear modulus (G*) over the range of blending temperatures. Given that the crumb rubber might dissolve and disperse into the bitumen, the mechanical properties of the modified binder could be enhanced. Another reason would be physical chemical properties of both bitumen and crumb rubber. In general, these properties are affected during interaction processes because rubber particle dimensions are reduced, and these are related to breakdown or depolymerisation of rubber particles digested in asphalt binders.15 Adding crumb rubber increased stiffness, thus yielding a higher failure temperature. At high blending temperature, the chemical reaction between rubber and bitumen binder saw to changes in binder properties. As expected, the rubber particles tend to swell due to the absorption 4 Brookfield viscosity results at 135°C 6 Phase angle results of all samples at 76°C Brookfield viscosity test results Materials Research Innovations 2014 VOL 18 SUPPL 6 S6-3 Mashaan and Karim Waste tyre rubber in asphalt pavement modification of aromatic oils, leading to the production of viscous gels.14 Phase angle (delta) result Figure 6 shows the effect of blending temperature and rubber content on the phase angle at 76°C. The blending temperature does affect the properties of rubberised binder in term of phase angle, and the increase in crumb rubber content also led to an obvious decrease of the phase angle of the rubberised binder. Thus, the primary reduction in the phase angle could be attributed to the effect of rubber content. Enhancing the rubber content led to the increase in carbon black reacting with the natural rubber, which corresponded to the elastic part of the crumb rubber chemistry. A phase angle (δ) represents the transition from viscous to elastic solid behaviours of bitumen binders. As mentioned in the literature review, the higher values of phase angles correspond to binders that become more viscous, while with lower value it tends to be more elastic. In general, this reflects a trade-off between high and low temperature performances of bitumen binders.9 Conclusions 1 S6-4 Based on this limited study on the utilisation of crumb rubber modifier in asphalt binders, the following findings were addressed: (i) According to laboratory binder tests, it is clear that rubber crumb content played a major role in influencing significantly the performance and rheological properties of rubberised bitumen binders. It could enhance the performance properties of asphalt pavement resistance against deformation during construction and road services. (ii) The results of binder tests on rubberised bitumen showed the increase in Brookfield viscosity, softening point and complex shear modulus, as well as reduced penetration and phase angle, means using crumb rubber modifier at 180°C significantly affect the performance properties of rubberised bitumen. (iii) The increase in rubber content by 20% showed a corresponding increase in Brookfield viscosity value that is higher than SHRP specification limits (3 Pas). As such, crumb rubber modifier content of 20% and above is not suitable as far as ease of pavement construction is concerned due to the high viscosity of the rubberised binder. Materials Research Innovations 2014 VOL 18 SUPPL 6 (iv) The conclusions arrived at from this research will involve promotion of sustainable technology through recycle waste material to produce a new material in an environment friendly manner. References 1. B. Adhikari, D. De and S. Maiti: ‘Reclamation and recycling of waste rubber’, Prog. Polym. Sci., 2000, 25, 909–948. 2. M. R. Ibrahim, H. Y. Katman, M. R. Karim and A. Mahrez: ‘Properties of rubberised bitumen mixes prepared with wet and dry mixing process’, ‘Proc 8th Int. Conf. of Eastern Asia Society for Transportation Studies’, Indonesia, 2009. 3. C. Thodesen, K. Shatanawi and S. Amerkhanian: ‘Effect of crumb rubber characteristics on crumb rubber modified (CRM) binder viscosity’, Construction Building Mater., 2009, 23, 295–303. 4. F. M. Nejad, P. Aghajani, A. Modarres and H. Firoozifar: ‘Investigating the properties of crumb rubber modified bitumen using classic and SHRP testing methods’, Construction Building Mater., 2012, 26, 481–489. 5. C. C. Wong and W. G. Wong: ‘Effect of crumb rubber modifiers on high temperature susceptibility of wearing course mixtures’, Construction Building Mater., 2007, 21, 1741–1745. 6. F. Xiao, P. E. Zhao and S. N. Amirkhanian: ‘Fatigue behavior of rubberized asphalt concrete mixtures containing warm asphalt additives’, Construction Building Mater., 2009, 23, 3144–3151. 7. J. Shen, S. N. Amirkhanian, F. Xiao and B. Tang: ‘Influence of surface area and size of crumb rubber on high temperature properties of crumb rubber and modified binders’, J. Construction Building Mater., 2009, 23, 304–310. 8. L. H. Lewandowski: ‘Polymer modification of paving asphalt binders’, Rubber Chem. Technol., 1994, 67, (3), 447–480. 9. F. J. Navarro, P. Partal, M. Garcia-Morales, M. J. Martin-Alfonso, F. F. Martinez-Boza, C. Gallegos and A. C. Diogo: ‘Bitumen modification with reactive and non-reactive (virgin and recycled) polymers: A comparative analysis’, J. Indus. Eng. Chem., 2009, 15, 458–464. 10. A. P. Paulo and C. P. Jorge: ‘Laboratory optimization of continuous blend asphalt rubber’, ‘Proc. 3rd European Pavement and Asset Management EPAM 3’, Coimbra, 2008. 11. P. Kumar, H. C. Mehndiratta and K. L. Singh: ‘Rheological properties of crumb rubber modified bitumen – A lab study’, J. Sci. Indus. Res., 2009, 68, 812–816. 12. H. U. Bahia and R. Davies: ‘Effect of crumb rubber modifiers (CRM) on performance-related properties of asphalt binders’, J. Assoc. Asphalt Paving Technologists, 1994, 63, 414–449. 13. H. U. Bahia and R. Davies: ‘Factors controlling the effect of crumb rubber on critical properties of asphalt binders’, J. Assoc. Asphalt Paving Technologists, 1995, 64, 130–162. 14. S. J. Lee, C. K. Akisetty and S. N. Amirkhanian: ‘The effect of crumb rubber modifier (CRM) on the performance properties of rubberized binder in HMA pavements’, Construction Building Mater., 2008, 22, 1368–1376. 15. S. K. Palit, R. K. Sudhakar and B. B. Pandey: ‘Laboratory evaluation of crumb rubber modified asphalt mixes’, J. Mater. Civil Eng., 2004, 16, (1), 45–53. Authors Queries Journal: Materials Research Innovations Paper: MRI_ICOSEM_103 Article title: Waste tyre rubber in asphalt pavement modification Dear Author During the preparation of your manuscript for publication, the questions listed below have arisen. Please attend to these matters and return this form with your proof. Many thanks for your assistance Query Reference Query 1 Please define ’SHRP’. Remarks