Bitumen Specifications

Agenda1. What is Bitumen? 2. Modes of Failure of Pavement3. Methods of Classification4. Test Methods

What is Bitumen?

What is Bitumen?Last residue obtained from fractional distillation of Crude OilIs black or dark brown in colourIs a visco-elastic materialDoes not have a distinct melting pointGradually softens when heatedMore solid at low temperatures and more liquid at high temperaturesHas adhesive propertiesHas water proofing propertiesForms good bond with a variety of aggregates

What are Performance Parameters?Mix and form a good bond with aggregate (at high temperature)Not melt on the road at highest atmospheric temperatureNot crack at extreme low atmospheric temperatureBe able to withstand repeated cycles of loading and unloadingBe able to withstand repeated cycles of temperature changeNot be inflammableBe free from impurities

What type of tests do we develop?Tests should be simpleTests should replicate the actual field conditions as accurately as possibleRate of change of properties with time, temperature and load should be measurable or predictable

Modes of Failure

Rutting/ Permanent Deformation

Fatigue Cracking

Low Temperature Cracking

Low Temperature Cracking

Methods of Classification

Methods of ClassificationPenetrationViscosity of TFOTViscosityPerformance

Penetration Based SystemMore than 100 years oldHas stood the test of timeBased on Penetration at 25 OCPenetration 30 to 100 are suitable for road constructionHarder grades suitable for heavier traffic loadsSofter grades suitable for light traffic loads

Viscosity Based SystemViscosity is considered to be the primary propertyMost tests over lap with that of Penetration based classificationClassified as VG 10, 20, 30 and 40 based on viscosity at 60OC

Viscosity of TFOT Residue Based SystemSimulates aging of BitumenViscosity ranging from 40 to 700 pascal seconds at 60OC are suitable for road constructionMost tests overlap with that of Penetration based classificationHigher viscosity for higher traffic and low viscosity for lower traffic

Performance Based SystemRadically different from Penetration & Viscosity based systemNew set of tests developed for better simulation of field conditionsLong term & short term aging taken into considerationClassification is based on the maximum and minimum pavement temperature that the Bitumen can withstand (PG 58 -22)

Test methods

Penetration TestArbitrary Empirical NumberDepth of penetration of a standard size needle under standard test conditionsVery easy to perform at field levelHelps in classification and traceability

Softening Point TestArbitrary test to indicate the temperature at which bitumen is more of a liquid and less of a solidHigher softening points indicate higher resistance to melting on roadHigher resistance to melting indicates higher rutting resistance

Ductility TestArbitrary empirical test to measure the cohesive strengthCohesive strength is loosely related to the fatigue strengthTesting temperatures may vary from country to country and from grade to grade also

Fraass Breaking PointTests low temperature propertiesThis mode of failure likely to take place only when temperatures are less than 0OC

Viscosity TestViscosity at 135OC is a fair indicator of the coating ability of BitumenViscosity at 65OC is a replacement for Softening Point test and is an indicator of the ability of Bitumen to resist rutting.

Thin Film Oven TestThis test simulates the process of aging of Bitumen during mixing and layingSample is kept in an oven at 163OC for 5 hoursTFOT aged bitumen can be tested for Penetration, Softening Point, Ductility, Viscosity, etc.

Other TestsPenetration ratio or penetration indexWax contentSpecific gravityWater contentMatter soluble in organic solventsFlash Point

Performance Grade Tests

Mixing and LayingTested in rotational viscometerMax. viscosity of 3 Pa-s at 135oC

Aging of BitumenDuring ConstructionEarly in Pavements lifePost construction upto two years Late in pavements lifeSeven plus years of life

Rolling thin film oven test (RTFOT)RTFOT + Pressure Ageing Vessel (PAV)

RuttingDue to melting of bitumen on the roadAlways occurs at max. pavement temp.Test to be conducted at max. pavement temp.Tested in Dynamic Shear RheometerComplex Shear Modulus G*/Sind min. 1 kPa, @ 10 rad/s for unaged bitumenG*/Sind min. 2.2 kPa, @ 10 rad/s for RTFOT aged bitumen

FatigueDue to repeated loading,unloading cyclesAlways occurs near the average pavement temp.Test to be conducted at average + 4OC pavement temp.Tested in Dynamic Shear RheometerFatigue Strength G*Sind max. 5000 kPa, @ 10 rad/s for RTFOT + PAV aged bitumen

Low Temp. CrackingDue to loss of elasticity at very low temp.Always occurs at lowest pavement temp.Testing done at min. temp. + 10OC Bending Beam RheometerCreep Stiffness of max. 300,000 kPa, Rate of Change of Creep with load (m-value) min. 0.30Direct Tension Test - For Modified BitumensFailure strain min. 1%

Performance Vs TestsRuttingFatigue CrackingDuctility

Fatigue Strength

Softening Point, Viscosity &Penetration after AgingFraass Breaking Point

Creep Stiffness

Rate of change of Creep

Failure StrainSoftening Point

Viscosity

Penetration

Complex Shear ModulusLow Temperature CrackingMixing and LayingViscosity at 135OC

Types of BindersTar

Natural Asphalt / Rock Asphalt / Lake Asphalt

Bitumen

TarCOKE OVEN TARProduced at temperatures above 1200OC during manufacturing of coke.High aromatic content.Pitch content - 50 %.LOW AROMATIC TAR Produced at temperatures 600OC to 700OC. Less viscous. Paraffinic in nature. Pitch content - 35 %.

Natural Asphalt / Rock Asphalt / Lake Asphalt

Naturally occurring Bituminous binder.Biggest deposits in Trinidad100 Acres,90 meter deep10 to 15 Million MT Pen - 5 maxAsphalt found in France, Italy & Switzerland - Rock Asphalt.

Bitumen Conventional Bitumen Paving Grade Bitumen Industrial Grade Bitumen

Cutback

Bitumen Emulsions

Modified Bitumen

Modified Bitumen Emulsions

B I T U M E N A VISCO - ELASTIC MATERIAL

Engineering Properties of BitumenBitumen is a visco-elastic material & its deformation under stress is a function of both temperature & loading timeAt higher temperature &/or longer loading timeBehave as viscous liquidsAt low temperature &/or short loading time Behave as elastic solidsThe intermediate range of temperatures, more typical of the conditions in service, result in visco-elastic behaviour.

The Stiffness Concept In solids :E = s ewhere E = Elastic modulus s = Stress e = Strain

The Stiffness ConceptIn visco-elastic material :St,T = s et,TWhere St,T = Stiffness modulus at specific time t & Temp. T. s = Stress et,T = Strain at specific time t & temp. T.

COMPOSITION B I T U M E N

Elemental AnalysisCarbon82 - 88 %Hydrogen 8 -11 %Sulphur 0 - 6 %Oxygen 0 -1.5 %Nitrogen 0 - 1 %

Chemical CompositionDecreases PenetrationIncreases PenetrationReduces Shear SusceptibilityIncreases Softening Point, reduces Penetration Index, increases Viscosity

BITUMEN PRODUTION PROCESSES

Refinery Operation

FIELD STORAGE

PUMPING STATION

LIGHT DISTILLATE

HEAVY DISTILLATE

PROCESSUNIT

ASPHALTCEMENTS

FOR PROCESSING INTOEMULSIFIED ANDCUTBACK ASPHALTS

STILL

AIR

AIRBLOWNASPHALT

STORAGE

TOWERDISTILLATIONREFINERY

RESIDUUM

OR

GAS

PETROLEUM

SAND AND WATER

CONDENSERS AND COOLERS

TUBEHEATER

MEDIUM DISTILLATE

Distillation is used to separate the various crude fractions by boiling point ranges. The crude oil is heated in a large furnace to about 343 oC and partially vaporized. The remaining material is transferred to a distillation tower. Different fractions reach their boiling point ranges at various heights in the tower. When the temperature is reduced, each material condenses on a tray and is drawn off at each level.

Bitumen Production ProcessAtmospheric DistillationVacuum DistillationAir Blowing of Short ResiduePropane Deasphalting

Atmospheric DistillationOnly very heavy Crudes like Boscan Crudes can be processedThe atmospheric unit can be adjusted in such a manner that the residue of the atmospheric unit meets the bitumen specifications without any alteration and can be directly used as bitumenVery little scope to control Bitumen properties

Vacuum DistillationHeavy Crudes like Arab Heavy can be processed

Vacuum Distillation Unit (Vacuum Tower Bottoms) may meet the specifications of paving grade bitumen without any further processing

Depending on origin of the crude, bitumen with penetration ranging form 35 to 300 can be produced directly from the Vacuum Distillation Unit

Still little scope for controlling the properties of Bitumen

Air Blowing of Short ResidueRelatively lighter Crudes can be used

The VTB is rectified by blowing hot air into it

The process is controlled by regulating the temperature, rate of blowing, duration of blowing and usage of catalyst

When hot air is blown into VTB the process of oxidation takes place resulting in increase in molecular weight. The increase in molecular weight is due increase in Asphaltenes and Resins accompanied by reduction in Aromatics and Saturates

Catalyst like Ferric Chloride, Phosphorus Pentoxide, Sulphuric Acid or Hydrochloric Acid can also be used to reduce the blowing time. However, the catalyst is consumed in the process of blowing and therefore strictly speaking it is not really catalytic reaction

Catalytic blowing results in bitumen with higher penetration for the same softening point

Propane DeasphaltingThis process takes advantage of the complex internal solubility parameters of bitumen

In the Propane Deasphalting process Propane or mixture of Propane and Butane in liquid state is introduced at the bottom of the column

Under controlled conditions the Aromatics get dissolved in Propane and the resultant material left at the bottom is Propane Deasphalted Asphalt

This has very high concentration of Asphaltenes and Resins and confirms to specifications of harder grades of Bitumen

This can be blended with VTB to get a wide variety of bitumen

Specifications andTest Methods

What is expected from Bitumen?Ensure road behaves in a predictable wayBitumen performs the desired function on the roadDoes not fail under predictable loadsResists deterioration of road with time Is able to withstand expected climatic conditionsMix easily and form strong bond with a wide variety of aggregatesIs safe to handleModified Bitumen and Bitumen Emulsions should be a stable mixture in storage and handling

What properties need to be tested?Hardness PenetrationWithstand high temperatures Softening PointWithstand repetitive loading/unloading DuctilityWithstand low temperatures Fraass breaking pointEase of mixing with aggregate Viscosity at 135OCSafety in handling - Flash pointPurity Solubility in TrichloroethyleneWeight to volume conversion Specific gravityDeterioration of properties w.r.t. time and temperature Thin Film Oven Test

Relationship Between Properties

Penetration at Softening Point 800

Viscosity at Softening Point 1200 Pa s (12000 poise)

Penetration at Fraass Breaking Pt 1.25Interdependencies

Properties B I T U M E N

Relationship between PropertiesPenetrationSoftening PointPenetration is approx. 800Viscosity is 1200 Pa sFraass Breaking PointPenetration is approx. 1.25Viscosity

Bitumen Test Data Chart

Optimal Viscosity for mixing & compaction

Selection

ofGRADE

Choice of GradeChoice of Bitumen is based on

Climatic Conditions - Maximum & Minimum temperature & rainfall.

Intensity of Traffic - Number of vehicles per day, Traffic speed & axle load of vehicles.

Applications of 30/40 GradeSuited for areas where diff. between min. & max. temp. < 25oC. Suited for traffic intensity > 1500 cv/ dayUsed in metropolitan areas.Used in airport runways.

Applications of 60/70 GradeMore viscous grade.Higher softening point.Suited for traffic intensity > 1500 cv/day.Can withstand heavier axle loads.Better suited for highways, expressways & urban roads. Suited for areas where difference between min. & max. temp. is > 25oC.Reduced stripping in presence of water.

Applications of 80/100 Grade Less viscous grade. Used in all climatic conditions. Suited for traffic load < 1500 cv/day. Better suited for high altitude/snow bound regions irrespective of traffic intensity.

Handling

ofBITUMEN

Aging of BitumenBitumen undergoes a process of aging with timeBecomes harder and brittleFactors affecting aging of bitumenHigh TemperatureAvailability of OxygenExposure to UV radiation

Aging of Bitumen

Normally Bitumen hardens by one grade during mixing and laying.

Advantages

AdvantagesSmooth

Safe

Economical

Speed

Quiet

Environment friendlyVersatile

State of-the-art

Stage Construction

Resistant to de-icing material

Serviceability

SmoothBetter riding qualityAbsence of jointsEstimated 15% increase in pavement life for 50% increase in smoothnessLess wear and tear to vehicleLesser fuel consumptionEnjoyable ride

SafeBetter skid resistance over a longer period of timeUse of OGFC reduces Tyre Spray, Hydroplaning and Improves VisibilityBetter contrast with pavement markings

EconomicalLow initial cost compared to PCCGap widens throughout pavement lifeA well designed and constructed pavement Can last for 25 to 34 years without reconstructionCan serve for 15 year or more before distresses become sufficient to require rehabilitation

Speed of ConstructionNewark Airport 1,15,000MT in 15 days, 11,000MT in 24 hoursPave during off peak hours and open to traffic as soon as it cools downReduces work zone accidentCan result in 80% reduction in user delay costs24-hour closure will have 3 to 10 times more vehicles pass through the work zone

Quiet PavementsDense graded asphalt is quieter by 2 to 3 dB(A) compared to PCC3 dB(A) corresponds to Doubling the distance in the line of sourceReducing traffic volume by 50%Reducing traffic speed by 25%Open graded Friction CourseReduces noise furtherCosts 1/8th of noise barrier on side of the roadAesthetically superior

Environment FriendlyUsed for water proofing of fish ponds without any problemVery low level of leachable compounds

Most recycled product in the world100% recyclableSecond highest - Aluminium cans 60%

Can use waste material from other fields also like worn out PCC

State-of-the-ArtRoad design, construction and maintenance methods are being overhauledNew tests being developedNew plants providing high quality materialsPavers with laser controlled screeds for even smoother pavementsBetter material transfer vehicles for uniformity and rollers with increased compactive effort. The ultimate result of this new technology will be: smoother, more durable, longer lasting asphalt pavements

Stage ConstructionBituminous pavements can be constructed in stagesBeing made thicker and/or wider as the need arisesEach successive layer becomes an integral part of the pavement structure, increasing the load carrying capacity.

De-icing MaterialsBituminous pavements are not harmed by de-icing chemicalsAlso snow and ice melt quickly from bituminous pavements

ServiceabilityBituminous pavements can easily maintain a high level of serviceability with minimal disruption to the traffic

Can be easily trenched, patched and quickly opened to traffic when underground utilities need to be repaired.

Versatile

Beautiful

MODIFIED BITUMENBinder of the future

Why Modified Bitumen? Demands on Road increasing every yearIncreasing Number of VehiclesIncreasing Axle Load Desire to maintain higher serviceability levelHigher fatigue resistanceHigher resistance to weatheringBetter adhesionHigher stiffness modulusLesser cracking, ravelling, deformation & creep failureReduce number of overlaysReduction in vehicle operation cost

Crumb Rubber Modified Bitumen

Bitumen+Additives (Modifiers/Treated Crumb Rubber)

Types of ModifiersTHERMOPLASTIC ELASTOMERSStyrene-butadiene-styrene(SBS)Styrene-butadiene-rubber (SBR)Styrene-isoprene-styrene (SIS)Styrene-ethylene-butadiene-styrene (SEBS)Ethylene-prppylene-diene terpolymer (EPDM)Isobutene-isoprene copolymer (IIR)Natural RubberCrumb RubberPolybutadiene (PBD)PolyisopreneTHERMOPLASTIC POLYMERSEthylene vinyl acetate (EVA)Ethylene methyl acrylate (EMA)Ethylene butyl acrylate (EBA)Atactic polypropylene (APP)Polyethylene (PE)Polypropylene (PP)Polyvinyl chloride (PVC)Polystyrene (PS)THERMOSETTING POLYMERSEpoxy resinPolyurethane resinAcrylic resinPhenolic resinCHEMICAL MODIFIERSOrgano-metallic compoundsSulphurLigninFIBRESCelluloseAlumino-magnesium silicateGlass fibreAsbestosPolyesterPolypropyleneADHESION IMPROVERSOrgainc aminesAmidesANTIOXIDANTSAminesPhenolsOrgano-zinc/organo-lead compoundsNATURAL ASPHALTSTrinidad lake Asphalt (TLA)GilsoniteRock asphaltFILLERSCarbon blackHydrated limeLimeFly ash

Types of ModifiersPolymersRubbersPlasticsThermoplasticLDPE, EVA, EBAThermosetEpoxy ResinsSynthetic ElastomersSBS, SBR etc.Crumb RubberChemically TreatedNatural Rubber(Latex)Plain

Selection Criteria Atmospheric Temperature OCMinimum Maximum45 10 CRMB 55 CRMB 55 CRMB 60

Quote: Based on the data analysis presented for the two pavements, an asphalt-rubber pavement would be more cost-effective than a conventional pavement with respect to agency costs as well as user costs. In addition, the good performance of the asphalt-rubber pavement would increase its service life, which in turn would have a substantial impact on life cycle cost analysis. Furthermore, if one or more rehabilitation is eliminated in a typical analysis period (35 years), it would also have a significant impact on user costs during the work zone periods. Unquote.Conclusions

New Trends

Future Trends in Bituminous Roads ISO Certification of RoadsRoad Safety AuditPerformance Based SpecificationsStone Mastic AsphaltPerpetual PavementsFoamed BitumenPolyphosphoric Acid Modified BitumenSulphur Extended Bitumen Modifiers

ISO Certification of RoadsGrowth in EN ISO 9000 certification in European countriesVoluntary activity driven by individual companies or by the national asphalt industry.To obtain management and marketing tools. In several countries certification is becoming a regulatory requirement, usually by mutual agreement between suppliers and clients. Effective quality schedules can be produced only by joint action of supplier and client side of road sector. If the positive aspects of certification are not taken into account in contract arrangements its introduction will increase the overall cost of asphalt roads

Road Safety AuditSafety audit applied toFresh project proposalsExisting network of roadsSpecific existing projectAuditors should be completely independent of the organization involved in development of project.The audit team comprising of 4-5 people inspect the roads during daytime and also at night.The team identifies aspects that the road controlling authority does well, as well as the aspects that could be improved.

Stone Mastic AsphaltIncreasingly popular Worldwide in heavy traffic roads & airfields.Even surface gives better riding comfort.Texture gives good skid resistance & relatively low traffic noise.Strong aggregate structure provided by the coarse aggregate particles gives excellent resistance to permanent deformation. Rich mastic, which fills the voids, makes SMA highly durable.Modified bitumen & Fibres can be used to further enhance the mechanical properties.Allows thin layer application.

Perpetual PavementsStructure Lasts 50+ years Bottom-Up Design and ConstructionIndefinite Fatigue LifeRenewable Pavement Surface.High Rutting ResistanceTailored for Specific Application Consistent, Smooth and Safe Driving Surface.Environmentally FriendlyAvoids Costly Reconstruction

Foamed BitumenMixture of Bitumen (98%), water (1%) and foaming agent (1%)When hot bitumen (160 to 200OC) comes in contact with cold water (15 to 25OC)Mixture expands more than 10 timesForms a fine mist or foamFoamed bitumen is sprayed on fine aggregate in mixing drums to get a strong flexible pavement materialUsed for durable, fast and low cost rehabilitation of existing pavements

Polyphosphoric Acid Modified BitumenLower stripping compared to other bitumensReduction in mixing and laying temperaturesImproves fracture strength and ductilityVery low dosage of modifierTest tracks in the world are still under evaluation but preliminary results are very promising

Sulphur Extended Asphalt ModifierOdourless pellets consisting of Sulphur, Plasticizers and additives Is added to the hot mixMelts and disperses easilyActs as binder extender and asphalt mix modifierEnvironmentally safeReduces Bitumen requirement by 30%Mixing temperature is reduced by 10OCHigher resistance to rutting, fatigue failure and low temperature crackingSuitable for perpetual pavements

Warm Mix AsphaltHelps in reduction of handling temperaturesLower emissionLower fuel costSome proprietary products available in international marketMay have to review the aging of bitumen as handling temperatures will be lowerResearch on at many places on Europe and USA.

Performance Grade SpecificationsExisting SpecificationsMost tests are empirical tests and are not directly related to performance on the roadTests are conducted at one standard temp.Performance under climatic condition prevailing throughout the year are not evaluatedOnly short term ageing is evaluated, that too only in a few casesPerformance grade tests simulate the actual field conditions in a more realistic way

PERFORMANCE GRADE BITUMEN

BITUMEN TODAYPenetration/Viscosity based classification80/100, 60/70, 30/40Penetration, Softening Point, Ductility, ViscosityEmpirical tests done at standard temp., loading, etc.Ageing is not consideredNo direct correlation with actual field conditions Seems to work somehow Has stood the test of timeNeed to cut inefficiencies Cost effectiveMore direct correlation between bitumen and road performance is needed

BITUMEN TOMORROWMore direct correlation between road performance and properties of bitumenProperties desiredEasier handling (mixing, coating, rolling) Better rutting resistanceHigher fatigue lifeResistance to low temperature cracking - New system of classification to be developed- New tests to be developed

CLASSIFICATIONPG 58 -22Performance GradeAverage 7 day max. pavement design temp.Min. pavement design temp.

MIXING AND LAYINGTested in rotational viscometerMax. viscosity of 3 Pa-s at 135oC

AGEING OF BITUMENDuring ConstructionEarly in Pavements lifePost construction upto two years

Late in pavements lifeSeven plus years of life

Rotating thin film oven test (RTFOT)RTFOT + Pressure Ageing Vessel (PAV)

ROTATING THIN FILM OVEN TEST

PRESSURE AGEING VESSEL

RUTTINGDue to melting of bitumen on the roadAlways occurs at max. pavement temp.Test to be conducted at max. pavement temp.Tested in Dynamic Shear RheometerG*/Sind min. 1 kPa, @ 10 rad/s for unaged bitumenG*/Sind min. 2.2 kPa, @ 10 rad/s for RTFOT aged bitumen

DYNAMIC SHEAR RHEOMETER

FATIGUEDue to repeated loading,unloading cyclesAlways occurs near the average pavement temp.Test to be conducted at average + 4OC pavement temp.Tested in Dynamic Shear RheometerG*Sind max. 5000 kPa, @ 10 rad/s for RTFOT + PAV aged bitumen

LOW TEMP CRACKINGDue to loss of elasticity at very low temp.Always occurs at lowest pavement temp.Testing done at min. temp. + 10OC Bending Beam RheometerCreep Stiffness of max. 300,000 kPa, m-value min. 0.30Direct Tension Test - For Modified BitumensFailure strain min. 1%

BENDING BEAM RHEOMETER

DIRECT TENSILE TESTER

PERFORMANCE EVALUATION

GRADE BUMPINGChoice of grade depends on max. and min. pavement temperature 20 mm below road surface.Correction for Traffic speed> 90 km/h - No Correction< 90 km/h - Increase one high temp. grade< 20 km/h - Increase two high temp. grade Correction for Traffic volume< 10 million ESAL - No Correction> 10 million ESAL - Increase one high temp. grade> 30 million ESAL - Increase two high temp. grade

SafeHandling Practices

Health, Safety & Environmental AspectsLow order of potential hazard provided good handling practices are observed.

Contains Polycyclic Aromatic Hydrocarbons. PCAs with molecular wt. Of 200 to 4500 are biologically active carcenogens. Concentration of these in Bitumen is extremely low.

Other than heat burns, hazards are negligible. However it is prudent to avoid prolonged & intimate skin contact.

Health, Safety & Environmental Aspects (contd.)In case of skin burns plunge the affected area under cold running water for 10 minutes.

When bitumen is heated or mixed with aggregate, fumes are emitted. The fumes contain particulate matter, Hydrocarbon vapours & very small amount of H2S. However, the concentration is rarely above permissible limits.

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