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Asphalt Binders. Introduction. Terminology / Uses Sources / Manufacturing Composition / Product Types Temperature Susceptibility Specifications / Testing Modifiers / Additives. Terminology. Asphalt/Bitumen
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Asphalt Binders ENCI 579
Introduction • Terminology / Uses • Sources / Manufacturing • Composition / Product Types • Temperature Susceptibility • Specifications / Testing • Modifiers / Additives ENCI 579
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 ENCI 579
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 ENCI 579
Asphalt Uses ENCI 579
Asphalt Uses ENCI 579
Asphalt Uses ENCI 579
Asphalt Uses ENCI 579
Asphalt Uses ENCI 579
Asphalt Uses ENCI 579
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 ENCI 579
Asphalt Sources • Tars - distillation of coal • Pitch is distillation residue of tar • Petroleum asphalts from crude oil ENCI 579
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 ENCI 579
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 ENCI 579
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 ENCI 579
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 ENCI 579
Refining Crude ENCI 579
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 ENCI 579
Constitution of Asphalt Asphalt - colloid multiphase mixture of millions of different components Identification by groups of components Asphalt heptane methanol+ toluene asphaltenes TCE toluene naphthene aromatics polar aromatics saturates ENCI 579
Asphaltenes • Dark brown or black solids insoluble in nonpolar solvents • Elemental composition varies only over narrow range Carbon : 82 3% Hydrogen : 8.1 0.7% • 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% ENCI 579
Asphaltenes ENCI 579
Resins • Dark semisolid or solid, very adhesive fractions • Soluble in liquids that precipitate asphaltenes C/H ratio : 7.5 ~ 9.1 Hydrogen : 9.5 ~ 11% • Polycyclic structures with 5~6 rings (2~3 aromatic on which there are aliphatic substituents ENCI 579
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 ENCI 579
Oils mono-, di-, polynuclear aromatics C/H ratio : 6.8 ~ 8 molecular weight : 240 ~ 800, most 360 ~ 500 ENCI 579
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) ENCI 579
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 ENCI 579
Asphalt Testing • Penetration • Viscosity (shear rate) • Softening Point (R & B) • Ductility • Flashpoint (COC, PM) • Solubility (TCE) • TFOT, RTFOT • Mass Loss, Aging Index ENCI 579
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 ENCI 579
