Crumb Rubber Modified Bitumen (CRMB)

Crumb Rubber Modified Bitumen (CRMB) is hydrocarbon binder obtained through physical and chemical interaction of crumb rubber (produced by recycling of used tyres) with bitumen and some specific additives.

1. Crumb Rubber Modified Bitumen BY ASHWANI KUMAR NMIT,BANGALORE

2. Bituminous Pa v em e nts – Life Cycle Is s ue AXLE LOAD WATER HEAT BITUMEN Poor susceptibility

3. Solution is MODIFIED BITUMEN MODIFIER BITUMEN

4. MODIFIERS Crumb rubber The scrap tyre is shredded into small pieces by the help of mechanical blades up to sizes of 1mm-75µm.

5. CRMB Development Charles McDonald ,an engineer with City of Phoenix, Arizona, US developed in 1960s.

6. Source of Crumb Rubber Crumb rubber is obtained from truck or automobile tyres . Whole truck tyres contain 18 % natural rubber compared to 9 percent in automobile tyre.

7. Production method It is produced from discarded rubber by two methods:- Ambient grinding Cryogenic grinding

8. Ambient Grinding Processed at or above ordinary room temperature Produces irregularly shaped ,torn particles with relatively large surface area

9. Cryogenic Grinding This process uses liquid Nitrogen to freeze C R. It has relatively lower surface area.

10. Method of mixing of CR in Bitumen Dry process Wet process

11. Dry Process Introduced by two S wedish company Crumb rubber as a substitute for a part of mineral aggregate

12. Wet Process Thoroughly mixing crumbs of CR with bitumen and allowing it to react for a period of 45min-1 hour. High temperature should be maintained.

13. CR-interaction Process

14. Comparison Ch a r a cteri s tic VG 10 VG 30 VG 40 C R M B -50 C R M B -55 C R M B -60 Penet r ati o n at 25º C , (0.1 m m , 100g, 5 Se c .) 80-100 50-70 40-60 < 70 < 60 < 50 Softe n in g P o in t, ºC (R&B), Mini m um 40 47 50 50 55 60 Fl ash Point, COC º C , Min 220 220 220 220 220 220

15. Waste tyre crumb for roads Globally o v er 1 5 m i ll i on t o nes of w a s te tyres are generated, annuall y . I nd i a a lso cont r i bu t es app r o x . 1 m i l l i o n tyres ann u all y . I f Waste tyre crumb is to b e u s ed with bit u m en fo r w earing course, an app r o x . 25 n o 's o f tyre waste can b e c on s u med in ro a ds eve r y d ay or 100 , 00 no's of waste tyre an n ual l y .

16. Advantages Lower susceptibility to daily & seasonal temperature variations. Higher resistance to deformation at elevated pavement temperature. Better adhesion between aggregates & binder. Prevention of cracking & reflective cracking. Overall improved performance under heavy traffic conditions.

17. Disadvantages The bitumen-rubber materials must be properly selected , designed & produced . Construction is more challenging as temperature requirement are more critical. It is not possible to store C R-MB at elevated temperature without equipping storage tanks with augurs.

18. Quality control requirements CRMB producer must obtain the viscosity curve for mix if the source of bitumen and/or crumb rubber changes. It should be agitated continuously. Compaction of asphalt mix containing CRMB should begin promptly to adequate compaction of pavement. Pneumatic- tyred rollers tend to pick up the asphalt mix containing CRMB and therefore , should not be used.

19. References “A Study on t he Performance of Crumb Rubber Modified Bitumen by Varying the Sizes of Crumb Rubber” by Nabin Rana Magar . “Quality control requirement for using crumb rubber modified bitumen(CRMB) in bituminous mixtures” by Prithvi Singh kandhal . “Recycled tyre rubber modified bitumens for road asphalt mixtures :A literature review” by Davide Lo Presti . “Laboratory comparison of the crumb-rubber and SBS modified bitumen and hot mix asphalt” by Baha Vural Köka , Hakan Çolak .

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