PAVES THE WAY. BITUMEN. Tar Natural Asphalt / Rock Asphalt / Lake Asphalt Bitumen. Types of Binders. Produced from Wood or Coal by destructive distillation process Coke Oven Tar Produced at temperatures above 1200 O C during manufacturing of coke. High aromatic content.
Natural Asphalt / Rock Asphalt / Lake Asphalt
BitumenTypes of Binders
Coke Oven Tar
Produced at temperatures above 1200OC during manufacturing of coke.
High aromatic content.
Pitch content - 50 %.
Low Aromatic Tar
Produced at temperatures 600OC to 700OC.
Paraffinic in nature.
Pitch content - 35 %.Tar
A VISCO - ELASTIC MATERIAL
In solids : process
E = s
where, E = Elastic modulus
e =StrainThe Stiffness Concept
Bitumen is a visco-elastic material & it’s deformation under stress is a function of both temperature & loading time
At higher temperature &/or longer loading time
Behave as viscous liquids
At low temperature &/or short loading time
Behave as elastic solids
The intermediate range of temperatures, more typical of the conditions in service, result in visco-elastic behaviour.Engineering Properties of Bitumen
In visco-elastic material : under stress is a function of both temperature & loading time
St,T = s
Where, St,T = Stiffness modulus at specific time t & Temp. T.
et,T= Strain at specific time t & temp. T.The Stiffness Concept
B I T U M E N
Carbon 82 - 88 % under stress is a function of both temperature & loading time
Hydrogen 8 - 11 %
Sulphur 0 - 6 %
Oxygen 0 - 1.5 %
Nitrogen 0 - 1 %Elemental Analysis
Increases Softening Point, reduces Penetration Index, increases Viscosity
Reduces Shear Susceptibility
Ensure road behaves in a predictable way under stress is a function of both temperature & loading time
Bitumen performs the desired function on the road
Does not fail under predictable loads
Resists deterioration of road with time
Is able to withstand expected climatic conditions
Mix easily and form strong bond with a wide variety of aggregates
Is safe to handle
Modified Bitumen and Bitumen Emulsions should be a stable mixture in storage and handlingWhat is expected from Bitumen?
Hardness – Penetration under stress is a function of both temperature & loading time
Withstand high temperatures – Softening Point
Withstand repetitive loading/unloading – Ductility
Withstand low temperatures – Fraass breaking point
Ease of mixing with aggregate – Viscosity at 135OC
Safety in handling - Flash point
Purity – Solubility in Trichloroethylene
Weight to volume conversion – Specific gravity
Deterioration of properties w.r.t. time and temperature – Thin Film Oven TestWhat properties need to be tested?
Penetration under stress is a function of both temperature & loading time
Fraass Breaking Pt
Choice of Bitumen is based on under stress is a function of both temperature & loading time
Climatic Conditions - Maximum & Minimum temperature & rainfall.
Intensity of Traffic - Number of vehicles per day, Traffic speed & axle load of vehicles.Choice of Grade
Less viscous grade. under stress is a function of both temperature & loading time
Used in all climatic conditions.
Suited for traffic load < 1500 cv/day.
Better suited for high altitude/snow bound regions irrespective of traffic intensity.Applications of 80/100 Grade
More viscous grade. under stress is a function of both temperature & loading time
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 60/70 Grade
Suited for areas where diff. between min. & max. temp. < 25 under stress is a function of both temperature & loading timeoC.
Suited for traffic intensity > 1500 cv/ day
Used in metropolitan areas.
Used in airport runways.Applications of 30/40 Grade
Bitumen hardens with time under stress is a function of both temperature & loading time
Softening Point increases
Factors affecting hardening
Surface area exposed to air
Exposure to UV radiationHardening of Bitumen
Normally Bitumen hardens by one grade during mixing and laying.
Bitumen mixing and laying.
Smooth mixing and laying.
Resistant to de-icing material
Better riding quality mixing and laying.
Absence of joints
Estimated 15% increase in pavement life for 50% increase in smoothness
Less wear and tear to vehicle
Lesser fuel consumption
Better skid resistance over a longer period of time mixing and laying.
Use of OGFC reduces Tyre Spray, Hydroplaning and Improves Visibility
Better contrast with pavement markingsSafe
Low initial cost compared to PCC mixing and laying.
Gap widens throughout pavement life
A well designed and constructed pavement
Can last for 25 to 34 years without reconstruction
Can serve for 15 year or more before distresses become sufficient to require rehabilitationEconomical
Pave during off peak hours and open to traffic as soon as it cools down
Reduces work zone accident
Can result in 80% reduction in user delay costs
24-hour closure will have 3 to 10 times more vehicles pass through the work zoneSpeed of Construction
3 dB(A) corresponds to
Doubling the distance in the line of source
Reducing traffic volume by 50%
Reducing traffic speed by 25%
Open graded Friction Course
Reduces noise further
Costs 1/8th of noise barrier on side of the road
Aesthetically superiorQuiet Pavements
Very low level of leachable compounds
Most recycled product in the world
Second highest - Aluminium cans – 60%
Can use waste material from other fields also like worn out PCCEnvironment Friendly
New tests being developed
New plants providing high quality materials
Pavers with laser controlled screeds for even smoother pavements
Better 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 pavementsState-of-the-Art
Being made thicker and/or wider as the need arises
Each successive layer becomes an integral part of the pavement structure, increasing the load carrying capacity.Stage Construction
Also snow and ice melt quickly from bituminous pavementsDe-icing Materials
Bituminous 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.Serviceability
Binder of the future
Demands on Road increasing every year serviceability with minimal disruption to the traffic
Increasing Number of Vehicles
Increasing Axle Load
Desire to maintain higher serviceability level
Higher fatigue resistance
Higher resistance to weathering
Higher stiffness modulus
Lesser cracking, ravelling, deformation & creep failure
Reduce number of overlays
Reduction in vehicle operation costWhy Modified Bitumen?
Bitumen serviceability with minimal disruption to the traffic
Additives (Modifiers/Treated Crumb Rubber)Crumb Rubber Modified Bitumen
THERMOPLASTIC ELASTOMERS serviceability with minimal disruption to the traffic
Ethylene-prppylene-diene terpolymer (EPDM)
Isobutene-isoprene copolymer (IIR)
Ethylene vinyl acetate (EVA)
Ethylene methyl acrylate (EMA)
Ethylene butyl acrylate (EBA)
Atactic polypropylene (APP)
Polyvinyl chloride (PVC)
Trinidad lake Asphalt (TLA)
Fly ashTypes of Modifiers
Types of Modifiers serviceability with minimal disruption to the traffic
SBS, SBR etc.
LDPE, EVA, EBA
Atmospheric Temperature serviceability with minimal disruption to the trafficOC
<35 35-45 >45
<-10 CRMB50 CRMB 55 CRMB 55
-10 to10 CRMB 50 CRMB 55 CRMB 60
>10 CRMB 55 CRMB 55 CRMB 60Selection Criteria
International Use of Crumb Rubber Modified Bitumen serviceability with minimal disruption to the traffic
UK Environmentalist’s want use of CRMB to be encouraged on roads. Govts. especially are considering making the use mandatory.
Belgian Road Research Center is encouraging the use of CRMB on Freeways
South African companies are increasingly using Rubber Modified mixes
International Use of Crumb Rubber Modified Bitumen
ISO Certification of Roads Africa.
Road Safety Audit
Performance Based Specifications
Stone Mastic Asphalt
Polyphosphoric Acid Modified Bitumen
Sulphur Extended Bitumen ModifiersFuture Trends in Bituminous Roads
Voluntary 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 roadsISO Certification of Roads
Safety audit applied to Africa.
Fresh project proposals
Existing network of roads
Specific existing project
Auditors 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.Road Safety Audit
Existing Specifications Africa.
Most tests are empirical tests and are not directly related to performance on the road
Tests are conducted at one standard temp.
Performance under climatic condition prevailing throughout the year are not evaluated
Only short term ageing is evaluated, that too only in a few cases
Performance grade tests simulate the actual field conditions in a more realistic wayPerformance Grade Specifications
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.Stone Mastic Asphalt
Structure Lasts 50+ years airfields.
Bottom-Up Design and Construction
Indefinite Fatigue Life
Renewable Pavement Surface.
High Rutting Resistance
Tailored for Specific Application
Consistent, Smooth and Safe Driving Surface.
Avoids Costly ReconstructionPerpetual Pavements
When hot bitumen (160 to 200OC) comes in contact with cold water (15 to 25OC)
Mixture expands more than 10 times
Forms a fine mist or foam
Foamed bitumen is sprayed on fine aggregate in mixing drums to get a strong flexible pavement material
Used for durable, fast and low cost rehabilitation of existing pavementsFoamed Bitumen
Lower stripping compared to other bitumens airfields.
Reduction in mixing and laying temperatures
Improves fracture strength and ductility
Very low dosage of modifier
Test tracks in the world are still under evaluation but preliminary results are very promisingPolyphosphoric Acid Modified Bitumen
Is added to the hot mix
Melts and disperses easily
Acts as binder extender and asphalt mix modifier
Reduces Bitumen requirement by 30%
Mixing temperature is reduced by 10OC
Higher resistance to rutting, fatigue failure and low temperature cracking
Suitable for perpetual pavementsSulphur Extended Asphalt Modifier