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Increase in environmental concerns has been leading to develop innovative and eco-friendly ideas to re-use the waste byproducts from industries and domestic use. Scrap tires are one of the world’s most troublesome solid waste problems. Every year more than 90000 tons of Crumb Rubber (waste tires) pile up in Bangladesh alone. Besides their sheer volume, bulky discards presents many problems in local landfill creating a global challenge. On the other hand, Bangladesh is a country with vast variation in temperature and the amount of rain is not uniform over the year. Over 90 percent of highways and roads of Bangladesh are constructed with flexible pavement. Most of the roads get deteriorated due to high temperature susceptibility and lower resistance to moisture induced damaged of the conventional bitumen used in Bangladesh. Increased traffic factors such as heavier loads, higher traffic volume and higher tire pressure demand higher performance pavements. So to minimize the damage of pavement surface and increase durability of flexible pavement, the conventional bitumen needs to be improved. So an undergrad research study has been made to evaluate the performance of Crumb Rubber Modified Bitumen (CRMB). As a first part of the study, an attempt has made to access the stabilization of the bitumen containing crumb rubber waste by performing basic tests such as Penetration Test, Ductility Test, Softening Point Test, and Flash & Fire Point Test.
Addition of Crumb Rubber has major effect on physical properties of bitumen. A significant decrease in penetration and ductility and considerable increase is in softening point, flash and fire points are observed with increasing percentage of Crumb Rubber. Lower penetration value making harder grade of bitumen, giving additional strength to the road and reduces water damage. The significant reduction in the ductility indicates a great loss in the flexibility of the base bitumen occurred by addition of small percent of crumb rubber. Higher softening point is required for better resilience of bituminous pavements. Thus, increase in softening point indicates that CRMB will be less susceptible to high temperature change and more resistance to rutting. The increment in both flash and fire points is around 20% with addition of Crumb Rubber. Finally, from the above discussions, it is clear that there is improvement in the physical properties of bitumen modified with Crumb Rubber. It is evident that the addition of CRM to the bitumen has shown an improvement in consistency and safety characteristics. On the basis of the performance of the modified bitumen, the range of optimum percentages of Crumb Rubber Waste has been selected as 10% of bitumen for the further investigations related to Marshall Mix Design.
Marshall Values, namely Marshall Stability Value, Marshall Flow Value, Voids Present in Air, Voids in Aggregates and Voids in Bitumen have been determined from the Marshall Stability, serves as a benchmark values to access the quality of Bituminous Pavement. After conducting Marshall Test on Pure Bitumen and Crumb Rubber Modified Bitumen (CRMB) and comparing their graphs, it have been found that Crumb Rubber Modified Mixture has a better results compared to the non-modified mixtures. Marshall Stability and Flow values as well as other Marshall values have been improved remarkably.
By studying the test results of common laboratory tests and Marshall Test on pure bitumen and crumb rubber modified bitumen it is concluded that properties of pure bitumen can be improved significantly by modifying it with addition of crumb rubber which is a major environment pollutant. CRMB provides much greater performance and it’s application can go beyond highway use to airport runways, landfill liners and many more uses. While other modified bitumen are patented processes, the fact that CRMB is a widely available public process assures countries like Bangladesh that they are paying fair market product. By using CRMB we get pavements that give better performance and higher quality that lasts longer than traditional bituminous road with half the material. Moreover, everyone benefits from elimination of dangerous tire piles and reduction of landfilling volume. The test results tells the story and the specifications are available today. That’s why Crumb Rubber is a pavement of choice for more and more countries around the world. Therefore in a country like Bangladesh, crumb rubber modified bitumen (CRMB) is suggested as one of the methods that might be able to solve the environmental problem and roadway pavement. Once for all, utilization of Crumb Rubber can be the beginning and dawn of a new era of transportation in Bangladesh.