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Asphalt Binders

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Introduction

• Terminology / Uses• Sources / Manufacturing • Composition / Product Types• Temperature Susceptibility• Specifications / Testing• Modifiers / Additives

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Terminology• Asphalt/Bitumen

– A mixture of heavy carbon-based compounds containing a high percentage of multiple-ring aromatics, many involving sulfur, nitrogen and oxygen atoms

– hydrocarbons soluble in CS2

– Brown-Black semi-solid material which is solid at room temp but softens and flows when heated

– Asphalt Cement - binder - oil• Asphalt Concrete - Pavement

– Asphalt Cement plus Aggregate

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Asphalt Uses• Paving Material• Preservative / Protection• Waterproofing / Roofing• Insulator / Adhesive / Lubricant• Industrial & Building Material• Fuel oil - Bunker, LIFO, MIFO• Conversion Feedstock

– produce lighter petroleum products - gasoline, diesel etc

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Asphalt Uses

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Asphalt Uses

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Asphalt Uses

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Asphalt Uses

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Asphalt Uses

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Asphalt Uses

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Asphalt Sources• Native or Natural Asphalts

– bitumens with inorganic impurities• Trinidad lake has 25-50% insolubles

– Asphaltites - no impurities, high asphaltene content• Gilsonite - Eastern Utah

– Rock Asphalts -- asphalt in rock• impregnated sandstones - Oklahoma• tar sands - Alberta• oil shales - Colorado

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Asphalt Sources

• Tars - distillation of coal– Pitch is distillation residue of tar

• Petroleum asphalts from crude oil

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Manufacturing

• Asphalts produced from crude oil• Crude Oil Taxonomy - 18 Classes

– Light, Intermediate, heavy– Sweet, Intermediate, Sour– Paraffinic, Napthenic

• Best crudes for paving asphalts are heavy napthenic crudes

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Crude Oil• Crude oil is found as a natural deposit on the

earth’s surface or buried up to 18,000 ft deep• First oil wells were drilled in China in 347 AD

using bits attached to bamboo poles and achieved depths up to 800 ft

• Modern oil era was originally driven by kerosene oil for lamps

• Edison’s light bulb reduced demand but was offset by internal combustion engine gasoline

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Petroleum Deposit of Western Canada

• Western Canada has the complete spectrum of hydrocarbons from light sweet crude to tar sands

• Generally oil is heavier towards the northeast. That is the closer to the Rockies, the lighter the crude.

• Lloydminister heavy oil can be produced by conventional means while Cold Lake can only be recovered by thermal stimulation

• The tar sands must be physically mined

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Refining Crude• Most impact on the asphalt properties is from the crude

source but the manufacturing process can also have an effect

• There are 80 refineries in North America producing asphalt - 5 in Western Canada

• Typically integrated refineries produce asphalt as a by-product, but there are dedicated asphalt refineries as well.

• Primary asphalt manufacturing is by fractional distillation

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Refining Crude

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Cracked Asphalts

• Very poor paving materials• breaking down large hydrocarbons into smaller molecules

through the application of temperature pressure and use of catalysts

• Thermal crackers• Cokers• Catalytic Cracking• Hydrocracking

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Constitution of AsphaltAsphalt - colloid multiphase mixture of millions of different

components

Identification by groups of components

Asphalt

heptane

asphaltenesTCE

polar aromatics

toluene

methanol + toluene

saturates naphthene aromatics

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Asphaltenes

• General belief that unaltered asphaltenes have a definite composition• Notable variation in the proportion of heteroatoms:

– Oxygen: 0.3 -4.9%– Sulphur : 0.3 - 10.3%– Nitrogen : 0.6 - 3.3%

• Dark brown or black solids insoluble in nonpolar solvents

• Elemental composition varies only over narrow rangeCarbon : 82 3%Hydrogen : 8.1 0.7%

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Asphaltenes

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Resins• Dark semisolid or solid, very adhesive fractions• Soluble in liquids that precipitate asphaltenes

C/H ratio : 7.5 ~ 9.1Hydrogen : 9.5 ~ 11%

• Polycyclic structures with 5~6 rings (2~3 aromatic on which there are aliphatic substituents

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Oils

• Lowest molecular weight hydrocarbons in asphalt • Similar to lubricating oils - highest boiling

fraction of lubricants• Control the harness of asphalt• Single or condensed naphthene and aromatic rings

with side chains of varying length

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Oils

mono-, di-, polynuclear aromaticsC/H ratio : 6.8 ~ 8molecular weight : 240 ~ 800, most 360 ~ 500

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Structure and Colloidal Properties of Asphalts

• Physical properties of asphalt = f (dispersion of asphatenes in maltenes)

• Peptizing effect of aromatic and resin portions of maltenes keep the colloidal structure of asphalt

• Prime consideration - rate of absorption of higher MW maltenes on the asphaltene particles = f(time, temperature)

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Structure and Colloidal Properties of Asphalts

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Asphalt Products

• Asphalt Cements– reduce viscosity by heating

• Cutback Asphalts– reduce viscosity by blending with a solvent– RC, MC, SC

• Asphalt Emulsions– Asphalt in water - or inverted– Anionic or Cationic - charge of particles– RS, MS, SS

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Asphalt Testing

• Penetration• Viscosity (shear rate)• Softening Point (R & B)• Ductility• Flashpoint (COC, PM)• Solubility (TCE)• TFOT, RTFOT• Mass Loss, Aging Index

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Specifications

• Classical Specifications were designed to describe the material not its performance

• Recent specifications (CGSB ) have incorporated some performance criteria

• Superpave specifications are used to define performance using new methods of measuring properties

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