Bitumen & Bituminous Materials Dr Ian M Lancaster
History Formed by Evaporation, oxidation and polymerisation of crude oil Natural deposits: Lake asphalt, rock asphalt, gilsonite Early uses: Waterproofing ships (Noah s Ark) Mortar for Walls (Babylon) Mummification (Egypt) Sealant for temples (3000 BC) Street of Procession (Babylon, 600 BC) Medication (until 1500 AD) 2
What is Bitumen? A dark-brown to black, highly viscous material obtained from the residue of processing suitable crude oils. In chemical terms: A complex mixture of aliphatic, aromatic and naphthenic hydrocarbons in combination with mono-, di- and poly-substituted heterocycles and heterosubstituted chains of varying molecular weight. The predominant hetero-atoms being oxygen, nitrogen and sulphur. 3
Crude oil composition 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% North Sea Russian Middle East S. American Gas Gasoline Diesel Lubes Bitumen 4
Bitumen Production 5
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Bitumen blending 1000 100 35 42 50 60 85 125 190 10 log PEN A %A + log PEN B %B 100 1 0 20 40 60 80 100 7
Specifications 8
Performance Attributes Adhesive Cohesive Waterproof Resilient Flexible Long-lasting (Thermoplastic) (Viscoelastic) 9
Why use Polymer-modified bitumen? To improve performance Rutting, fatigue, fuel resistance To increase pavement lifetime To solve specific pavement problems Point loading Torque stress Fuel resistance To allow changes in design Reduced thickness 10
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Bitumen Behavior - Thermoplastic Hot Soft Fatting up Cold Brittle Fretting Difference between softening point and brittle point should be as great as possible 12
Bitumen Behaviour - Viscoelastic Spring Elastic (rigid) High Speed Dashpot Viscous (Soft) Low Speed 13
Effects of Modification Change in Basic Properties Increase in Softening Point Decrease in Penetration Increase in Viscosity Lower Fraass Brittle Point (also function of base binder) Improved Performance Rheological Properties Rutting & Fatigue Cohesion Tensile Properties Ductility Thermal Cracking 14
Category of Modifier Thermosetting polymers Elastomeric polymers Thermoplastic polymers Chemical modifiers Fibres Anti-stripping agents Natural binders Fillers Fluxes Examples of Generic Types Epoxy resin Polyurethane resin Acrylic resin Natural rubber Styrene-butadiene-styrene (SBS)block copolymer Styrene-butadiene rubber (SBr) Styrene-ethylene/butylene-styrene (SEBS) block copolymer Styrene-isoprene-styrene block copolymer (SIS) Ethylene-propylene-diene terpolymer (EPDM) Isobutene-isoprene copolymer (IIR) Ethylene vinyl acetate (EVA) Ethylene butyl acrylate (EBA) Ethylene methyl acrylate (EMA) Polyethylene (PE) Atactic polypropylene (APP) Polyvinyl chloride (PVC) Polystyrene (PS) Synthetic waxes Organo-metal complexes Lignin Sulfur Cellulose Glass fibre Polyester Polyamide Asbestos Alumino-magnesium silicate Organic amines Amides Phosphates Trinidad Lake Asphalt (TLA) Gilsonite Carbon black Fly ash Lime Hydrated Lime Iron oxides Heavy mineral oil Light mineral oil Vegetable oil 15
Plasticity range Premium Polymer Mid Range Polymer 350/500 Fraass R&B 40/60 160/220-40 -20 0 20 40 60 80 100 16
Cohesion Cohesion /Jcm -2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 Premium 100pen Mid-range 0 20 40 60 80 100 Temperature / C 17
Ductility Tensile Properties Low extension rate Elasticity Unmodified binders low ductility zero recovery Modified binders high(er) ductility good recovery Ductility = Cracking 18
Stiffness Tensile Properties 350 300 250 200 150 100 50 Paving grade Plastomer Elastomer 0-50 0 50 100 150 200 250 300 Elongation 19
Rutting 60 50 40 30 20 10 100/150 70/100 40/60 PMB1 PMB2 0 1 10 100 1000 10000 100000 1000000 20
Rutting 21
Strain (microstrain) Fatigue 10000 1000 Plastomer Unmodified Elastomer 100 100 1000 10000 100000 Cycles to failure 22
Fibre modification Drainage control Increase binder content Increase viscosity Reduce drainage Reduce workability Increase stiffness 23
Bituminous Mixtures Dense Impermeable Divert water from the structure Open Porous, permeable, semi-permeable Conduct water through the structure 24
Material Specifications EN13108 Part 1 Asphaltic Concrete Part 4 Hot Rolled Asphalt Part 5 Stone Mastic Asphalt Part 7 Porous Asphalt PD6691 How to do it PD6692 How to test it 25
Hot Rolled Asphalt Key Requirement: Stiff, yet flexible mortar to reduce rutting Binder with high softening point / viscosity Application General use Prevention of water ingress Bridges High performance with PmB / high stone content 26
Stone Mastic Asphalt Key Requirement: Thick binder film to minimise aging fibres Ease of handling / compaction Polymer modified for flexibility & durability Application General use to high performance Care binder content. compaction cooling 27
SMA / Porous Asphalt Thick film improves durability oxygen Stone-stone contact binder must absorb stresses 28
Ageing control Low mixing temperatures Short storage times Local delivery Low paving temperatures Dense mixes Thicker binder films 29
Effects of Ageing Higher Softening Point Lower Penetration Higher Viscosity More Brittle Chemically Different more asphaltenes & resins less saturates & aromatics Risk of Pavement Failure 30
Asphaltic Concete Key requirement Application dependent Structural layers (EME) Stiff, flexible binder (10/20 or 15/25) Footway application Compliant, easy to lay. 31
Best practice road note 42 Core asphalt principles Pavements should act as one layer Joints are weaknesses Seal & bond layers Asphalt virtues High binder content Small aggregate size Low voids Prevent water ingress Maintain drainage 32
Taking oil further 33