14-08-2012, 12:59 PM
RUBBERISED BITUMEN FOR ROAD WORKS
FINAL SEMINAR REPORT OF RBFRW.docx (Size: 416.08 KB / Downloads: 287)
INTRODUCTION
Development of infrastructural facilities like road is vital for the economic growth of a country and also roadways are considered as one of the most important elements of infrastructure and they play an essential role in our daily lives. Good roads improve connectively, accessibility, mobility and productivity.
In India, it is estimated that over 33 lakh kilometers of road exists. The road transport carries close to 90% of passenger traffic and 70% of freight transport.
Over the years, road structures have deteriorated more rapidly due to increases in service traffic density, axle loading and low maintenance services. To minimize the damage of pavement surface and increase durability of flexible pavement, the conventional bitumen needs to be improved with regards to performance related properties, such as resistance to permanent deformation (rutting) and fatigue cracking and Increasing pressure by the vehicular traffic on the road is compelling highway authorities to look for high performance bitumen as such the modification of bituminous binder has been explored over the past years in order to improve road pavement performance properties.
Investigations in India and countries abroad have revealed that properties of bitumen and bituminous mixes can be improved to meet requirements of pavement with the incorporation of certain additives or blend of additives. These additives are called “Bitumen Modifiers” and the bitumen premixed with these modifiers is known as modified bitumen.
HISTORY AND PRESENT STATUS:
IN WORLD
The earliest experiments date back to the 1840s, which Involved incorporating natural rubber into bitumen to increase its engineering performance properties. The process of bitumen modification involving natural and synthetic rubber was introduced as early as 1843. Then, in 1923, natural and synthetic rubber modifications in bitumen were further improved (Isacsson and Lu 1999; Yildrim, 2007). According to the study of Yildrim (2007), the development of rubber-bitumen materials being used as joint sealers, patches and membranes began in the late 1930s. In 1950, the use of scrap tyre in asphalt
In 1960, Charlie Mac Donald working as head material engineer in Phoenix, Arizona, used ground tyre rubber as an additive in bitumen binder modification. He found that after completing the mixing of crumb rubber with the conventional bitumen and allowing it to blend for mix duration of 45 to 60 min, there were new material properties produced, which resulted in swelling in the size of the rubber particles at higher temperatures allowing for higher concentrations of liquid bitumen contents in pavement mixes (Huffman, 1980). In the mid-1980s, the Europeans began the development of newer polymers and additives for use in bitumen binder modification (Brule, 1996). In recent years, the use of crumb rubber has gained interest in pavement modification and has shown that crumb tyre rubber can improve the bitumen performance properties (Brown et al., 1997).
BINDER USED IN ROAD CONSTRUCTION
BITUMEN
Bitumen is final product that obtained when crude petroleum product is refined. Bituminous materials or asphalts are extensively used for roadway construction, primarily because of their excellent binding characteristics and water proofing properties and relatively low cost. Bituminous materials consists of bitumen which is a black or dark colored solid or viscous cementitious substances consists chiefly high molecular weight hydrocarbons derived from distillation of petroleum or natural asphalt, has adhesive properties, and is soluble in carbon disulphide. Tars are residues from the destructive distillation of organic substances such as coal, wood, or petroleum and are temperature sensitive than bitumen. Bitumen will be dissolved in petroleum oils where unlike tar.
Rubber Modified Bitumen
Proper blending of bitumen with natural rubber in a fixed proportion confers good elastic recovery to the blend. Incorporation of 2-4 per cent natural rubber into bitumen thus improves the properties of the later substantially and rubberized bitumen is found to be an excellent binder for rubble and sand. The rubberized bitumen formed minimizes permanent deformation due to overload on the road. This bitumen is unaffected by changes in atmospheric temperature and improve skid resistance due to increased aggregate retention and elimination of bleeding. Rubber increases the resistance to flow of bitumen at high temperature and improves the resistance to brittle fracture at low temperature. The above properties increase the service life of rubberized roads in many cases to more than 100% when compared to that of bituminous roads. Thus, rubberisation of roads will combine savings with safety.
Technique of rubberisation
Basically rubberized bitumen comprises of a bituminous compound into which rubber in a suitable form and proportion is incorporated using an appropriate technique. Rubberized bitumen is then used in pavings using conventional road building techniques. Following the incorporation and uniform distribution of rubber, bitumen undergoes radical changes in its properties depending to a large extent on the type and grade of rubber used, ratio of bitumen to rubber and the method of incorporation of rubber into bitumen.
It has been clearly established that for maximum effectiveness, the rubber must dissolve in the binder (bitumen). When properly incorporated, rubber increases the viscosity, strength and heat resistance of the system. Though different polymers have been tried for modification of bitumen for road works, very good results are reported in the case of Natural Rubber modified bitumen and Crumb Rubber Modified Bitumen
Natural Rubber Modified Bitumen (NRMB)
Natural Rubber is a naturally occurring polymer, and a very good one, when added to bitumen it will increase its elasticity, decrease its brittle point and increase its softening point. Natural rubber is usually added to the bitumen part of a material in the form of a liquid latex metered into the mixing drum by a pump system, or it should be.
The latex is supplied in metal drums of varying sizes according to what quantities are being used, the latex has quite a long storage life while in the sealed drums (and frost free) several months at least.
Because rubber is added to the bituminous material in this way, only as much latex is used as is needed, and means small tonnages of modified material are able to be produced at reasonable cost.When using proprietary polymer modified bitumens it is usually the case that a supplier will have to purchase at least a fifteen tonne tanker of binder, this can rule out small tonnage jobs because the cost of the modified mixture has to allow for the cost of buying the tanker load of bitumen, also pre-modified bitumen is not able to kept in storage for long periods.
Crumb Rubber Modified Bitumen (CRMB)
In recent times, a serious problem that leads to environment pollution is the abundance and the increase of waste tyre disposal. Large amounts of rubbers are used as tyres for cars and trucks. Despite the long run in service, these tyres are not discarded. Although, the rubber as a polymer is a thermosetting material cross linked to processing and moulding, however, it cannot be softened or remoulded by re-heating unlike other types of thermoplastics polymer which can be softened and reshaped when heated. The major approach to solve this issue is the recycle and reuse of waste tyre rubber and the reclaim of rubber raw materials like Crumb Rubber Modified Bitumen (CRMB).
CONCLUSION
Addition of rubber in any form to bitumen produces favourable changes in the properties of bitumen. It is found that rubberised bitumen was able to overcome the disadvantages of conventional bitumen roads, which melt during summer and become brittle during winter.
FINAL SEMINAR REPORT OF RBFRW.docx (Size: 416.08 KB / Downloads: 287)
INTRODUCTION
Development of infrastructural facilities like road is vital for the economic growth of a country and also roadways are considered as one of the most important elements of infrastructure and they play an essential role in our daily lives. Good roads improve connectively, accessibility, mobility and productivity.
In India, it is estimated that over 33 lakh kilometers of road exists. The road transport carries close to 90% of passenger traffic and 70% of freight transport.
Over the years, road structures have deteriorated more rapidly due to increases in service traffic density, axle loading and low maintenance services. To minimize the damage of pavement surface and increase durability of flexible pavement, the conventional bitumen needs to be improved with regards to performance related properties, such as resistance to permanent deformation (rutting) and fatigue cracking and Increasing pressure by the vehicular traffic on the road is compelling highway authorities to look for high performance bitumen as such the modification of bituminous binder has been explored over the past years in order to improve road pavement performance properties.
Investigations in India and countries abroad have revealed that properties of bitumen and bituminous mixes can be improved to meet requirements of pavement with the incorporation of certain additives or blend of additives. These additives are called “Bitumen Modifiers” and the bitumen premixed with these modifiers is known as modified bitumen.
HISTORY AND PRESENT STATUS:
IN WORLD
The earliest experiments date back to the 1840s, which Involved incorporating natural rubber into bitumen to increase its engineering performance properties. The process of bitumen modification involving natural and synthetic rubber was introduced as early as 1843. Then, in 1923, natural and synthetic rubber modifications in bitumen were further improved (Isacsson and Lu 1999; Yildrim, 2007). According to the study of Yildrim (2007), the development of rubber-bitumen materials being used as joint sealers, patches and membranes began in the late 1930s. In 1950, the use of scrap tyre in asphalt
In 1960, Charlie Mac Donald working as head material engineer in Phoenix, Arizona, used ground tyre rubber as an additive in bitumen binder modification. He found that after completing the mixing of crumb rubber with the conventional bitumen and allowing it to blend for mix duration of 45 to 60 min, there were new material properties produced, which resulted in swelling in the size of the rubber particles at higher temperatures allowing for higher concentrations of liquid bitumen contents in pavement mixes (Huffman, 1980). In the mid-1980s, the Europeans began the development of newer polymers and additives for use in bitumen binder modification (Brule, 1996). In recent years, the use of crumb rubber has gained interest in pavement modification and has shown that crumb tyre rubber can improve the bitumen performance properties (Brown et al., 1997).
BINDER USED IN ROAD CONSTRUCTION
BITUMEN
Bitumen is final product that obtained when crude petroleum product is refined. Bituminous materials or asphalts are extensively used for roadway construction, primarily because of their excellent binding characteristics and water proofing properties and relatively low cost. Bituminous materials consists of bitumen which is a black or dark colored solid or viscous cementitious substances consists chiefly high molecular weight hydrocarbons derived from distillation of petroleum or natural asphalt, has adhesive properties, and is soluble in carbon disulphide. Tars are residues from the destructive distillation of organic substances such as coal, wood, or petroleum and are temperature sensitive than bitumen. Bitumen will be dissolved in petroleum oils where unlike tar.
Rubber Modified Bitumen
Proper blending of bitumen with natural rubber in a fixed proportion confers good elastic recovery to the blend. Incorporation of 2-4 per cent natural rubber into bitumen thus improves the properties of the later substantially and rubberized bitumen is found to be an excellent binder for rubble and sand. The rubberized bitumen formed minimizes permanent deformation due to overload on the road. This bitumen is unaffected by changes in atmospheric temperature and improve skid resistance due to increased aggregate retention and elimination of bleeding. Rubber increases the resistance to flow of bitumen at high temperature and improves the resistance to brittle fracture at low temperature. The above properties increase the service life of rubberized roads in many cases to more than 100% when compared to that of bituminous roads. Thus, rubberisation of roads will combine savings with safety.
Technique of rubberisation
Basically rubberized bitumen comprises of a bituminous compound into which rubber in a suitable form and proportion is incorporated using an appropriate technique. Rubberized bitumen is then used in pavings using conventional road building techniques. Following the incorporation and uniform distribution of rubber, bitumen undergoes radical changes in its properties depending to a large extent on the type and grade of rubber used, ratio of bitumen to rubber and the method of incorporation of rubber into bitumen.
It has been clearly established that for maximum effectiveness, the rubber must dissolve in the binder (bitumen). When properly incorporated, rubber increases the viscosity, strength and heat resistance of the system. Though different polymers have been tried for modification of bitumen for road works, very good results are reported in the case of Natural Rubber modified bitumen and Crumb Rubber Modified Bitumen
Natural Rubber Modified Bitumen (NRMB)
Natural Rubber is a naturally occurring polymer, and a very good one, when added to bitumen it will increase its elasticity, decrease its brittle point and increase its softening point. Natural rubber is usually added to the bitumen part of a material in the form of a liquid latex metered into the mixing drum by a pump system, or it should be.
The latex is supplied in metal drums of varying sizes according to what quantities are being used, the latex has quite a long storage life while in the sealed drums (and frost free) several months at least.
Because rubber is added to the bituminous material in this way, only as much latex is used as is needed, and means small tonnages of modified material are able to be produced at reasonable cost.When using proprietary polymer modified bitumens it is usually the case that a supplier will have to purchase at least a fifteen tonne tanker of binder, this can rule out small tonnage jobs because the cost of the modified mixture has to allow for the cost of buying the tanker load of bitumen, also pre-modified bitumen is not able to kept in storage for long periods.
Crumb Rubber Modified Bitumen (CRMB)
In recent times, a serious problem that leads to environment pollution is the abundance and the increase of waste tyre disposal. Large amounts of rubbers are used as tyres for cars and trucks. Despite the long run in service, these tyres are not discarded. Although, the rubber as a polymer is a thermosetting material cross linked to processing and moulding, however, it cannot be softened or remoulded by re-heating unlike other types of thermoplastics polymer which can be softened and reshaped when heated. The major approach to solve this issue is the recycle and reuse of waste tyre rubber and the reclaim of rubber raw materials like Crumb Rubber Modified Bitumen (CRMB).
CONCLUSION
Addition of rubber in any form to bitumen produces favourable changes in the properties of bitumen. It is found that rubberised bitumen was able to overcome the disadvantages of conventional bitumen roads, which melt during summer and become brittle during winter.