Technical Seminar ReportON
Uses of Rubber modified bitumen and Crumb rubber modified bitumenSubmitted as a part of course curriculum
BACHELOR OF TECHNOLOGY IN DEPARTMENT OF CIVIL ENGINEERING 2012-13
Submitted by: G.S.NISHANK (09B91A0124) IVTH YEAR
GURU NANAK INSTITUTIONS TECHNICAL CAMPUS SCHOOL OF ENGINEERING & TECHNOLOGY[Affiliated to JNTU-Hyderabad NBA and NAAC accredited]
IBRAHIMPATNAM RR DISTRICT-501506(A.P)1
INDEX
Introduction Objective What is asphalt..? Why is rubber mixed with asphalt..? What is the need for modifying asphalt..? Common types of modified asphalt or bitumen Rubber modified bitumen Benefits of NRMB Possible problems of NRMB Applications of NRMB Crumb rubber modified bitumen Methods of crumb rubber modified bitumen Advantages of CRMB Applications of CRMB Comparison of performance characteristics of NRMB over CRMB Conclusion
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EVALUATION SHEET
Name of the candidate: G.S.NISHANK
Roll No:09B91A0124
Uses of Rubber modified bitumen and Crumb rubber modified bitumen
REPORT SUBMISSIONTAGET DATE SUBMISSION DATE RECIEVERS SIGNATURE
PPT SUBMISSIONTAGET DATE SUBMISSION DATE RECIEVERS SIGNATURE
REMARKS BY THE REVIEW COMMIITEE
NAME OF THE EVALUATOR
MARKS
Maximum Marks
Awarded Marks
Signature of the Supervisor
Signature of the HOD
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SEMINAR REPORT ON Uses of Rubber modified bitumen and Crumb rubber modified bitumen Subject- Concrete Technology
REPORT BY G.S.NISHANK (09B91A0124)
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INTRODUCTION:Roadways are considered one of the most important elements of infrastructure and they play an essential role in our daily lives and facilities for the economic growth of a country. Good roads improve connectively, accessibility, mobility and productivity. Generally bitumen is used for the pavements but bitumen in its pure form is not suitable for modern pavements and undergoes too many types of failure during service time. This is the reason for interests in bitumen modification field have grown and usage of rubber and its products with bitumen is being practiced for several years by now and has also shown good results. In road pavement construction, the use of natural and crumb rubber for the modification of bitumen binder is considered as a smart solution for sustainable development by reusing waste materials. The waste rubber was incinerated, landfilled and dumped illegally under water before it was used for the modification of bitumen which could lead to serious environmental problem. Thus by using this wastes we can reduce the environmental issues to great extent. Natural Rubber Modified Bitumen (NRMB) is widely used in road construction which is obtained by adding natural rubber latex to boiling bitumen where as crumb rubber modified bitumen (CRMB) is obtained from the scrap tyres which helps in improving bitumen binder performance properties of hot mix asphalt. This study aims to present and discuss the findings from some of the studies, on the use of crumb rubber and natural rubber in asphalt pavement.
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Objective:This seminar is focused as a brain storming session on emerging areas of developments in field of construction technology. Young and upcoming engineers should take advantage by getting advanced knowledge about the uses of natural rubber modified bitumen and crumb rubber modified bitumen. It will provide a unique opportunity to the emerging students to present their innovative ideas in these thrusts areas. The main objective of this seminar is to present the uses of natural rubber modified bitumen and crumb rubber modified in the construction of roads. The usage of these materials with bitumen will provide strength, stability and has longer life when compared to the normal bitumen. Through this technique we can use the waste rubbers by recycling which will reduce the environmental degradation caused by the waste rubbers and ensures betterment in the environmental condition
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What is asphalt? The word bitumen is also known as asphalt which is derived from the French word asphalte and it is also known as moom in Persian language.
Fig. Asphalt. Naturally occurring bitumen is also known as crude bitumen from which refined bitumen is obtained. Bitumen is a black liquid or semisolid form of petroleum which is highly viscous and sticky. Bitumen consists 80% of carbon, 15% of hydrogen and the remaining 5% is the combined mixture of oxygen, sulphur, nitrogen and other trace elements. Aggregates used for asphalt mixtures are crushed rock, sand, gravel or slags. Bitumen helps in binding these aggregates into a cohesive mixture. This gives the pavement the ability to distribute the loads of the traffic before it arrives at the formation level. It has high molecular weight, thermoplastic hydrocarbon constituent It is found in a large number of petroleum crude oils. It is non-crystalline in nature and is soft when hot and hard when cooled.
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Why rubber is mixed with asphalt? Tires have great engineering properties, they dont crack in the cold or melt in the heat. They have a wider range of performance temperatures than asphalt.
A good grip is maintained between the vehicles and the pavement. It helps in reducing the cracks in pavements.
Fig. Rubber binding the aggregates. Increase asphalt content and asphalt film thickness. Prevent bleeding, flushing, and drain-down. An aid to increase performance life. Less maintenance is required. Save money in project cost through reduced thickness. Increase safety and reduce noise. Distributes traffic loads.
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What is the Need for modifying Asphalt?Unmodified asphalt can be sensitive to the following considerations such as: Temperature variations Brittle in cold temperatures Thermal Cracks Softens in high temperatures Rutting and surface deformations Modification makes asphalt more temperature stable
Common types of modified asphalt or bitumen:Generally bitumen is mainly classified into four types as follow: Natural rubber modified bitumen Crumb rubber modified bitumen Polymer modified bitumen Bitumen emulsion
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RUBBER MODIFIED BITUMEN:Rubber modified bitumen is also known as natural rubber modified bitumen (NRMB). Natural rubber is melted and is mixed with bitumen and other aggregates such that it binds the material together. Among various forms of rubber used, it is seen that rubber latex is the best form of rubber that can be incorporated into bitumen. The initial process for the production of NRMB was mostly in-situ mixing of natural rubber latex with bitumen. For this the bitumen was heated to about 140:C and small amounts of (1%) of kerosene was added as viscosity modifier. To the boiling bitumen , natural rubber latex about 2 to 4% by weight of bitumen was added , stirred well and kept for about 2 hrs for homogenization. Uniformly blended NRMB thus obtained was used for the urbanization of roads Rubberisation was first experimental in Kerala way back in 1974 when a 1km Stretch of the MC road was paved with Natural Rubber Modified Bitumen (NRMB). Though the experiments was successful there were not many takers for the process, mainly because of the shortage of quality NRMB. After a long time Kochi Refineries started commercial production of rubberised bitumen in 1999. The Refineries is having a commercial plant with a production capacity of 15000 tons per year at a cost of Rs. 40 lakhs Asphalt Rubber or rubber modified bitumen is produced from recycled tires and consumes an estimated 12 million tires annually About 300 million waste tires per year were generated by the US alone In the 90s and only 17% of it were used in new products the rest took up space in landfills or were illegally dumped In todays markets approximately 80% of scrap tires generated are being used Presently estimates are less that 10% of scrap tires are disposed of in landfills.
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Benefits of NRMB:The advantages of the use of rubber-modified bitumen may be thus summarized as below:
Asphalt with admixture of rubber is more durable, resistant to fissures, frost and high temperatures What is more that it is very rough and has a good grip that shortens our breaking distance by 25 % There is also one more interesting thing, because this modified asphalt is noiseless and makes even 6 decibels less noise that normal one The improvements using rubber modified asphalt include decreased thermal cracking, deformation, and ice formation..etc. It ensures extended road life up to three times longer than normal asphalt Better resistance to fatting up or bleeding of bitumen under hot condition Improved skid resistance Low repairs and maintenance cost (about 33% savings) Reduces environmental pollution by less consumption of bitumen Conserves energy, natural resources and bitumen. Enhances tyre rolling and save fuel Less affected by changes in temperature The effect of rubber is to increase the resistance to flow at high temperature and at the same time improve the resistance to brittle fracture at low temperature. Rubberized bitumen shows improved adhesion with aggregates. Rubberisation of roads will create additional demand for natural rubber and it will ensure a remunerative price for rubber farmers
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Possible problems of NRMB : The disadvantages of rubber modified asphalt may be thus summarized as below: It was found to be time consuming and sometimes the mixing was not uniform due to lack of experience of the workers The asphalt separate into two or more phases, because of the weak interaction between the rubber particle surface and the asphalt. Normal asphalt shows a separation of between 2 to 4 % during heated storage. Rubber modified asphalt yields a non-homogeneous blend with up to 25% separation. This non-homogeneity reduces the reliability of the product properties. Separation decreases the expected life of the rubber modified asphalt It is usually necessary for the NRMB to be held in a tank that is capable of being agitated in someway, as the polymers being of a different density to the bitumen tend to separate if kept in storage for prolonged periods. The polymer additive can be destroyed by too high temperature for a long period of time after mixing The binder storage times should be kept as short as possible or deterioration of the polymer may take place
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APPLICATIONS of NRMB: Natural rubber modified bitumen is particularly recommended in places where the traffic intensity is the highest, and where there is a trouble with proper surface maintenance road surfaces with traffic congestion, junctions and access roads, to cover old destroyed and cracked concrete pavements, to cover old cube stone surface, surfaces of the runways and landing paths at airports, layer pavement in areas that are exposed to large deformations, for instance mining damage.
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Crumb rubber modified bitumen:Crumb Rubber is Vulcanised wasted rubber which has been ground down to a desired mesh size for addition to new compound as a filler. Also is called ground rubber. CRMB is a high performance Crumb Rubber Modified Bitumen manufactured using finely powdered scrap tyre rubber and other additives compatible with bitumen processed in a sophisticated reactor at high temperatures. Complex processing modifies the properties of Bitumen and imparts additional strength, elasticity and other beneficial properties to make it better able to withstand high traffic loads, extreme weather conditions and other forms of stress.
CRMB is manufactured in three grades for differing weathering conditions. Grade 50 is used for colder climates where minimum modification is sufficient. Grade 55 is used in moderate climatic conditions where moderate modification is required. Grade 60 is used in hot conditions where high modification is required to withstand the extra heat.
Temperature is the key for good paving with CRMB. Due to the high viscosity of the mix, the paving unit must have good traction, with four-wheel traction or tracks. Particular care should be paid to the discharging area, as the product is much more sticky Compacting should be done with steel roller, 10/12 tones, or a combination of steel and rubber, with care not to let the tires cool down - otherwise the bitumen will stick immediately. The black crumb rubber is produced from whole tyre scrap.It is available from 18 mesh up to 40 mesh.14
Crumb rubber powder is totally free from metal, fluff etc. Crumb rubber is being extensively used in road construction. It is in great demand by hot-mix construction plants as its usage has resulted in better durability & life of roads. CRMB is generally supplied in bulk, in tankers for ease of handling. It may also be supplied in 200 Kg barrels on request.
Methods of Crumb rubber modified bitumen:Three common methods of modification: Wet Process Rubber is added to liquid asphalt before mixing at the hot plant, rubber is wet before mixing with aggregates. Rubber blended with asphalt at the asphalt mix facility CR content 18 20% Dry Process - Rubber is added at the same time the asphalt and aggregate are mixed, rubber is dry before mixing with the aggregate. Rubber added to mixture either fine or coarse CR content 5 25% Terminal Blend Rubber is blended with asphalt and stored as liquid CR content 5 15%
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Scrap tyres modified to roads:
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Advantages of CRMB: Homogenous product free from perennial problem of phase separation. It has better edge resistance properties Improved adhesion between aggregate and binder ensures longer life ,strength and stability Higher resistance to deformation at elevated pavement temperature Higher fatigue life of mixing due to high elastic recovery Delay of cracking and reflective cracking. Lower susceptibility to daily and seasonal temperature variations Improved ageing resistance Improved resistance to stripping / moisture damage High Marshall stability Overall improved performance in extreme climatic and under heavy traffic conditions Does not require change in construction practices / machinery Cost effective Better water resistance Prevents rutting and provides resistance to creep and higher indirect strength Increased rutting resistance at elevated temperatures Excellent storage and thermal (performance) stability
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Applications of CRMB:CRMB can be used for wearing courses at heavy traffic roads, busy intersections, bridge decks etc.. for increased life of surfacing Rubberized asphalt has a number of uses, including spray and hot mix applications. Chip seals Water proofing concrete structures Hot Mix Asphalt Hot Applied Seal Coats (AC15-5TR) Crack Fillers / Joint Sealers Bridge Deck Coatings Tack Coats Used near high rainfall region For snow bound areas Sand asphalt Busses and trucks parking place Airport runway and parking apron Industrial and multi modal platforms Ground cover under playground equipment and in children parks. Running tracks, sports and playing fields. Horse arena flooring.
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Comparison of performance characteristics of NRMB over CRMB:
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CONCLUSION:Natural rubber modified bitumen and crumb rubber modified bitumen have their own uses but when compared NRMB is more favourable in withstanding the problems occurred by nature, 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. Conclusions drawn from the present study are: The roads surfaced with NRMB provide atleast 50% more service life than normal bitumen roads. Reduction in the road maintenance cost by 30%. Enhances tyre rolling and save fuel by 10%. Reduces traffic noise pollution. More comfort riding. The cost of production is 100% more but is more useful in the longer run Life of NRMB is more when compared to CRMB
Hence, road users would be ensured of safer and smoother roads. Furthermore, the use of NRMB and CRMB as an additive in bitumen modified binder would reduce pollution problems and protect our environment as well.
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