MODIFIED BITUMEN-Product, Purpose, Advantages Including Global and Indian

Scenario

Dr Sunil BoseDeputy Director

Central Road Research InstituteNew Delhi

TYPICAL PROBLEMS IN INDIA

• Severe Overloading

• Extreme variation of climatic conditions

• Premature cracking of pavements

LIMITATIONS OF CONVENTIONAL BITUMEN

• BRITTLENESS AT LOW TEMPERATURE• BECOMES SOFT IN HOT CLIMATIC CONDITIONS• HIGH TEMPERATURE SUSCEPTIBILITY• SUSCEPTIBLE TO VISCOELASTIC DEFORMATION (RUTTING)• FATIGUE FAILURE (CRACKING)

POOR ADHESION

CRRICRRI

CRACKING AT LOW TEMPERATURE

Hot Temperature Failure, Rutting

CRRICRRI

Bitumen produced by the traditional

methods of vacuum reduction and

air blowing of petroleum crude can not

meet all the requirements of increasing

severe service conditions namely :

1. Roads with high traffic intensity of

expressways & highways

2. Road locations subjected to heavy traffic

stress e.g. bus stops, intersections,

roundabouts & bridge decks.

3. Reflection cracks in bituminous overlays

over cracked concrete pavements

4. Urban roads where reduced surfacing

thickness is desired

5. Surfacing for low temperature snow

bound areas

6. Airfield surfacing where high stiffness

and thermal stability is required

A S0LUTION FOR ALL THESE PROBLEMS LIES IN USE OF POLYMER MODIFIED BITUMEN

WHAT ARE POLYMERS?

When small chemical units, called monomers, are

joined together in chains they form polymers.

When monomers such as styrene and butadiene

are reacted into chains, for example, they form

polystyrene and polybutadiene, respectively.

EFFECTS OF POLYMERS ON BITUMEN PROPERTIES

Reduced temperature

Susceptibility resulting in :

Increased stiffness at high

Road temperatures

(reducing permanent deformation)

Reduced stiffness at low road

Temperatures

(reduced cracking)

Classification of Polymer Modifiers

There are mainly two types of polymers used for development of Polymer Modified Bitumen (PMB)

Thermoplastic:

Plastomers: e.g low density Polyethylene (LDPE)

Ethylene Vinyl Acetate (EVA)

Elastomers: Ethylene Butyl Acrylate (EBA).

Styrene Butadiene Rubber (SBR)

Styrene Butadiene Styrene (SBS)

Polyisoprene, chloroprene

Polybutadiene, Ethylene Ter Polymer

Natural Rubber,

Waste Tyre Rubber

Thermosets :

Epoxy Resins

Properties Improved by Rubber/Polymer

A sufficient increase in viscosity, prevents

plastic deformation.

An increase in flexibility and elasticity of

binder at low temperatures to delay the crack

formation (mainly due to fatigue failure) and

loss of chipping.

High thermostability, improved homogeneity and

aging resistance, thus helping to reduce the

hardening of the binder during mixing, laying and

pavement service life.

Development of PMB

• Melting Behaviour of Polymers LDPE - 114 ° C EVA - 90 ° C Ethylene Ter Polymer - 60 ° C • Degradation Behaviour Above 250 ° C

Basic Blending Plant

~15-20 HP

~100RPM

Temperature of Asphalt 160 °C.

Ability to add polymers

Polymer’s Interaction with Bitumen

Polymer Dispersed in Bitumen

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Polymer’s Interaction with Bitumen

Bitumen Dispersed in Polymer

Polymer’s Interaction with Bitumen

Polymer Network in Bitumen

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Polymer’s Interaction with Bitumen

Polymer Network Grafted to Bitumen

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PRODUCT (MODIFIED BITUMEN)

Be compatible with bitumen

Resist degradation of bitumen at mixing temperature

Be capable of being processed by conventional mixing and laying

machinery

Produce coating viscosity at application temperature

Maintain premium properties during storage, application

and in service

Be cost-effective on a life- cycle-cost basis.

Advantages of PMB

- Lower susceptibility to daily and seasonal

temperature variations

- Higher resistance to deformation at elevated

pavement temperature

- Better age resistance properties

- Higher fatigue life of mixes

- Better adhesion between aggregates

and binder

- Prevention of cracking and reflective

cracking

- Overall improved performance in

extreme

climatic conditions and under heavy traffic

conditions.

Extreme climatic conditions require different grades of bitumen similar to

different grades of engine oil in vehicles

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With Polymer Modification, use the same bitumen for areas with extreme climatic

conditions

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APPLICATIONS OF POLYMER AND RUBBER MODIFIED BITUMEN

Stress Absorbing Membranes (SAM)

Stress Absorbing Membranes Interlayer

(SAMI)

Renewal courses as a part of maintenance

High traffic loads, e.g., Highways and

Airfield Pavements

Flexural Fatigue Test

Apply Cyclic load till failure

37.6mmX37.6 mm X200 mmsizeMix Beam

Measured Strain0

2

4

6

8

1 0

1 2

0 1 2 3 4 5 6 7 8 9 1 0 1 1

100 Cycles/Minute

FLEXURAL – FATIGUE LIFE RESULTS

Beam Size- 200 mm x 37. 6 mm x 37.6 mm (Temp

25 °C )

SAMPLE CYCLES SAMPLE CYCLES

TO FAILURE TO FAILURE

A 80/100 4500 A+2 % LDPE 4080

B 60/70 11500 A+5 % LDPE 4800

A+2 % SBS 48802 A+10% LDPE 750

A+5% SBS 91000 A+2 % PE+2% EVA 10840

A+10% SBS 63800 A+2% PE+5% EVA 14750

A+2% EVA 4900 B+2 % PPW 8800

A+5% EVA 8800 B+1% HTPB 46500

A+10% EVA 10100 B+2% HTPB 16500

Global scenario

Modifiers as an individual or as a group

of materials have made successful path

into the road and other construction

industries in advanced countries.

Elastomer modified binders

(SBS, SBR, SIS) 75%

Plastomer modified binders

(EVA, LDPE, EMA, EBA) 15%

Rubber and other miscellaneous

modified bituminous binders 10%

APPLICATIONS AND TYPE OF MODIFIERS

USED IN DIFFERENTCOUNTRIES

INDIAN SCENARIO

LABORATORY RESEARCH

In India, the Flexible Pavements Division

of CRRI initiated laboratory research on

polymer modified bitumen in 1980. Since

then number of polymer/rubber modifiers

were investigated for their feasibility of

using for hot mix as well as cold mix

paving applications.

These modifiers are :

LDPE

EVA

SBS

GILSONITE

NATURAL RUBBER

POLYBUTADIENE RUBBER

ETHYLENE TER POLYMER

SYNTHETIC RUBBER

PLASTIC WASTE

SEALOFLEX

STARFLEX

CRUMB/TYRE RUBBER

CHEMICALLY TREATED CRUMB

RUBBER

Field Trials : Field trials using PMB products patented by CRRI

were carried out in different climatic regions of

India. A list of such trials is given below :

R-54 Ministry of Surface Transport

Research Scheme

• Test Tracks were laid on NH-2 on

Kanpur Varanasi with Bitumen

Modified with LDPE, EVA, SBS

and

Crumb Rubber

PMB Test Tracks using SBS and

EVA were laid on :

NH-3 near Bombay

SH-45 Km. 308.8 to 309.0 Joshimath

Badrinath Road

Manali Kulu Road

Hindustan Tibet Road near Shimla

Chemically Treated Crumb Rubber- Test Tracks were laid on NH-1 near Ambala

- Ring Road Opposite Rajghat near Delhi

Natural Rubber Modified Bitumen- M.C. Road Trivandrum

ETHYLENE TERPOLYMER Jaipur Agra Road near Jaipur

Goa Airfield

PERFORMANCE OF TRIAL SECTIONS

• Periodic performance evaluation of test

section laid with PMB/CRMB upto five

years after construction proved their better

performance over conventional surfacing.

• Maintenance period of 12 years on a

National Highway with a heavy traffic, two

renewal coats will be enough instead of

three as required under the existing

specification.

• The use of SAMI of modified bitumen in

between old surface having extensive

cracks and renewal coats, extends life of

renewal by 2-3 years.

• The cost of periodic maintenance may be

reduced by 20-30 Percent.

PMB Road after 7 years

CRRI

Extensive potholes on the existing surface

prior to laying

Hump formation due to bleedingon the existing surface

Ravelling on the surface before laying the test section

Cracking on the existing surface before laying of test section

View of the test section in 2003

Surface condition of test section in 2006

Crumb Rubber Modifier for Use in Modified Bitumen

CONSTRUCTION OF A PMB SECTION IN PROGRESS

Laying in progress

View of Ahmedabad

Vadodara

Expressway

CRMB SECTION ON NH-8

EXTENSION OF LIFE BY USE OF PMB/CRMB

SPECIFICATION COST(Rs)/m2

LIFE(Years)

EXTRA LIFE(Years)*

25 mm Thick SDBC – 60/70 70 3-4 -125 mm Thick BC – 60/70* 80 4 –5 --25 mm Thick BC – 80/100* 74 4 –5 --25 mm Thick BC – 60/70 96 5-6 +1SAM-CRMB 28 4-5 --SAMI+25 mm Thick BC – 80/100 102 6-7 +2SAMI+25 mm Thick BC – 60/70 108 6-7 +2SAMI+40 mm Thick BC – 80/100 110 7-8 +3SAMI+40 mm Thick BC – 60/70 116 7-8 +3SAMI+25 mm Thick BC (CRMB) 116 7-8 +325 mm Thick BC (EVA+LDPE) 90 7-8 +325 mm Thick SDBC (SBS) 88 7-8 +325 mm Thick SDBC (EVA+LDPE) 84 6-7 +225 mm Thick BC (CRMB) 84 6-7 +3

* with reference to 25 mm thick BC of conventional bitumen, cost 1999