crumb rubber modified bitumen (crmb)
Post on 17-Jan-2017
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Crumb Rubber Modified Bitumen BYASHWANI KUMARNMIT,BANGALORE
Bituminous Pavements Life Cycle Issue
Solution isMODIFIED BITUMENMODIFIERBITUMEN
MODIFIERSCrumb rubberThe scrap tyre is shredded into small pieces by the help of mechanical blades up to sizes of 1mm-75m.
CRMB DevelopmentCharles McDonald ,an engineer with City of Phoenix, Arizona, US developed in 1960s.
Source of Crumb RubberCrumb rubber is obtained from truck or automobile tyres .
Whole truck tyres contain 18 % natural rubber compared to 9 percent in automobile tyre.
Production methodIt is produced from discarded rubber by two methods:-
Ambient GrindingProcessed at or above ordinary room temperature
Produces irregularly shaped ,torn particles with relatively large surface area
Cryogenic GrindingThis process uses liquid Nitrogen to freeze CR.
It has relatively lower surface area.
Method of mixing of CR in Bitumen
Dry ProcessIntroduced by two Swedish company
Crumb rubber as a substitute for a part of mineral aggregate
Wet ProcessThoroughly mixing crumbs of CR with bitumen and allowing it to react for a period of 45min-1 hour.
High temperature should be maintained.
ComparisonCharacteristicVG 10VG 30VG 40CRMB-50CRMB-55CRMB-60
Penetration at 25 C,(0.1 mm, 100g, 5 Sec.)80-10050-7040-60< 70< 60< 50
Softening Point, C
(R&B), Minimum40 4750505560Flash Point, COCC, Min220220220220220220
Waste tyre crumb for roadsGlobally over 15 million tones of waste tyres are generated, annually. India also contributes approx. 1 million tyres annually.If Waste tyre crumb is to be used with bitumen for wearing course, an approx. 250 no's of tyre waste can be consumed in roads every day or 100,000 no's of waste tyre annually .
AdvantagesLower 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.
DisadvantagesThe 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 CR-MB at elevated temperature without equipping storage tanks with augurs.
Quality control requirementsCRMB 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.
ReferencesA Study on the 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 modied bitumen and hot mix asphalt by Baha Vural Kka , Hakan olak.