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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