Asphalt Paving Materials Bituminous Materials Bitumenalso known as - PowerPoint PPT Presentation

Asphalt Paving Materials

Bituminous Materials Bitumen—also known as asphalt or tar—is a black, oily, viscous form of petroleum, which is a naturally occurring organic byproduct of decomposed plants. Natural bitumen is the thickest form of petroleum there is, and is made up of 83% carbon, 10% hydrogen and lesser amounts of oxygen, nitrogen, sulfur, and other elements. CIVL 3137 2

Bituminous Materials Bituminous Materials Natural Tar & Petroleum Asphalts Pitch Asphalts (late 1800s) (late 1800s) (early 1900s) CIVL 3137 3

Natural Asphalt Rock Asphalt Asphalt Sand Native Asphalt CIVL 3137 4

Rock Asphalt Asphalt rock is formed when natural layers of petroleum harden in the pores of sedimentary rocks such as limestone or sandstone. Over time, the lighter components evaporate away leaving material that ranges in consistency from a thick liquid to a crumbly sand or stone. Only about 5% to 15% of the composition of asphalt rocks is asphalt. CIVL 3137 5

Rock Asphalt CIVL 3137 6

Rock Asphalt ROCK ASPHALT & OIL SHALE IN KENTUCKY CIVL 3137 7

Asphalt Sands Asphalt sands (also called oil or tar sands) are either loose sands or partially consolidated sandstone containing a mixture of sand, clay, water, and bitumen. It is increasingly used as a source for crude oil thanks to technological developments such as steam extraction. CIVL 3137 8

Asphalt Sands CIVL 3137 9

Asphalt Sands CIVL 3137 10

Asphalt Sands CIVL 3137 11

Native Asphalt Native asphalts are seepages of natural asphalt that rise to the surface from deeper oil-bearing rocks and collect in depressions on the ground surface. The lighter components evaporate to leave behind a viscous or semi-solid deposit. The asphalt is so viscous you can walk on the surface. But if you stand on the surface for too long, you will slowly sink into it! CIVL 3137 12

Native Asphalt CIVL 3137 13 Source: Geological Society of Trinidad and Tobago (www.gstt.org)

Native Asphalt CIVL 3137 14

La Brea “Tar” Pits Wilshire Blvd CIVL 3137 15

Pitch Lake, Trinidad CIVL 3137 16

Pitch Lake, Trinidad CIVL 3137 17 http://www.flickr.com/photos/striderv/4314238332/lightbox/

Pitch Lake, Trinidad CIVL 3137 18

Pitch Lake, Trinidad CIVL 3137 19

Pitch Lake, Trinidad CIVL 3137 20

Pitch Lake, Trinidad CIVL 3137 21

Pitch Lake, Trinidad CIVL 3137 22

Bituminous Materials Bituminous Materials Natural Tar & Petroleum Asphalts Pitch Asphalts (late 1800s) (late 1800s) (early 1900s) CIVL 3137 23

Tar / Pitch Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a variety of organic materials such as coal, wood, or peat. The material is heated without oxygen (so the source material doesn’t burn) until the tar liquefies and seeps out. CIVL 3137 24

Wood Tar Wood tar (primarily made from pine wood) has many uses as a disinfectant, a flavoring agent for candies and alcohol, a spice for meat, and a water repellant. It is also used in cosmetics and anti-dandruff shampoos. Turpentine and charcoal are the byproducts of wood tar distillation. CIVL 3137 25

Wood Tar Kiln, Sweden https://en.wikipedia.org/wiki/Tar CIVL 3137 26

Coal Tar Coal tar is produced by heating coal without oxygen to produce coke and oil gas. Coal tar was used to construct the first surfaced roads. This is where we get the term “tarmac” or “tar macadam”. Today it can still be found in some parking lot sealers though it’s being phased out due to environmental and health concerns. CIVL 3137 27

Dunlap, TN Coking Ovens CIVL 3137 28

Chickamauga Coking Ovens CIVL 3137 29

Pennsylvania Coking Ovens CIVL 3137 30

Bituminous Materials Bituminous Materials Natural Tar & Petroleum Asphalts Pitch Asphalts (late 1800s) (late 1800s) (early 1900s) CIVL 3137 31

Petroleum Asphalt Petroleum asphalt is produced as a byproduct of crude oil distillation. It is the fraction of the crude oil with the highest boiling point (greater than 500°C) so it represents the residual left over after everything else (gasoline, kerosene, diesel, etc.) has boiled off in the distillation process. CIVL 3137 32

Crude Oil Chemistry Oils (Hydrocarbons) Resin-coated asphaltenes CIVL 3137 33

Crude Oil Light Crude Heavy Crude “oils” “oils” “oils” “oils” Aromatic Saturated (oils) Hydrocarbons Hydrocarbons CIVL 3137 34

Atmospheric Distillation Butane & Propane 1-4 Carbons Distillation Column Gasoline - 70°C 1-4 Carbons Naphtha - 120°C 5-10 Carbons Kerosene - 170°C 10-14 Carbons Crude Diesel Oil - 270°C 15-38 Carbons  400ºC Tube Heater Topped Crude 38-70 Carbons CIVL 3137 35

Vacuum Distillation Vacuum Light Gas OIl Medium Gas OIl Heavy Gas Oil Topped Crude Heat Bitumen Residuum (Asphalt Cement) Vaporizes the topped crude without using excessive heat (“cracking”) CIVL 3137 36

Crude Oil Gasoline Kerosene 6 21 Lt. Gas Oil 7 33 14 Hv. Gas Oil 26 10 20 28 16 Bitumen 58 Residuum 30 27 Nigeria Boscan Arabian Light Venezuela Heavy CIVL 3137 37

Petroleum Asphalt Petroleum asphalt at room temperature is very stiff. In order to mix it with aggregate to make asphalt concrete, it has to be liquefied. CIVL 3137 38

Liquefying Asphalt Cement Asphalt Cement (Bitumen Residuum) Heat Thin it with Suspend it solvents it in water Hot-Mix Cutback Emulsified Asphalt Asphalt Asphalt CIVL 3137 39

Temperature-Viscosity Peanut Butter Ketchup Chocolate Syrup Honey AASHTO T-245 MARSHALL COMPACTING TEMP. RANGE (280 +/- 30 cSt) Tomato Juice AASHTO T-245 MARSHALL MIXING TEMP. RANGE (170 +/- 20 cSt) Vegetable Oil CIVL 3137 40

Liquefying Asphalt Cement Asphalt Cement (Bitumen Residuum) Heat Thin it with Suspend it solvents it in water Hot-Mix Cutback Emulsified Asphalt Asphalt Asphalt CIVL 3137 41

Cutback Asphalt Cutback asphalt is asphalt cement that has been blended with a solvent in order to reduce its viscosity. After a cutback asphalt is applied the solvent evaporates leaving behind asphalt cement residue on the surface to which it was applied. A cutback asphalt is said to “cure” as the petroleum solvent evaporates away. CIVL 3137 42

Cutback Asphalt Cutback asphalt is classified according to the rate at which it cures (fast, medium, slow) and the viscosity of the liquid. The curing rate is a function of the boiling point of solvent used. The viscosity is based on how much solvent is used. CIVL 3137 43

Cutback Asphalt Grade 30 70 250 800 3000 Solvent Asphalt 30-60 70-140 250-500 800-1600 3000-6000 Kinematic Viscosity @ 140°F (in centistokes) CIVL 3137 45

Cutback Asphalt Rapid Curing (RC) Asphalt cement thinned with gasoline or naphtha Used for tack and seal coats (surface applications) Medium Curing (MC) Asphalt cement thinned with kerosene Used for prime coats, cold-laid pavement bases Slow Curing (SC) Asphalt cement thinned with diesel oil or gas oils Used for cold-laid pavement bases CIVL 3137 46

Liquefying Asphalt Cement Asphalt Cement (Bitumen Residuum) Heat Thin it with Suspend it solvents it in water Hot-Mix Cutback Emulsified Asphalt Asphalt Asphalt CIVL 3137 47

Emulsified Asphalt Emulsified asphalt is a suspension of very small asphalt cement droplet in water, which is assisted by an emulsifying agent (e.g., soap) that disrupts the surface tension of the water and imparts an electrical charge to the surface of the asphalt cement droplets so that they do not coalesce into larger droplets and fall out of suspension. CIVL 3137 48

Emulsified Asphalt hydrophilic group(s) Asphalt droplet hydrophobic component CIVL 3137 49

Emulsified Asphalt Asphalt Asphalt droplet droplet Repulsion between negative surface charges prevents coalescence CIVL 3137 50

Emulsified Asphalt CIVL 3137 52

Emulsified Asphalt Cationic Emulsifier Anionic Emulsifier LIMESTONE SILICA CIVL 3137 53

Emulsified Asphalt Emulsified asphalts appear as a thick brown liquid when first applied. When the asphalt droplets start to adhere to the aggregate the color changes to black and the emulsion is said to “break” (i.e., separate). As the water evaporates, the emulsion behaves more like pure asphalt cement. Once all the water has evaporated, the emulsion is said to have “set”. CIVL 3137 54

Emulsified Asphalt There are three main emulsion grades: rapid set, medium set and slow set. The terms relate to the amount of time it takes for the emulsion to set and the amount of mixing that can be performed before the emulsion breaks. Slow setting emulsions can stand up to more mixing than fast setting emulsions. CIVL 3137 55

Emulsified Asphalt Rapid Setting (RS or CRS) Used for surface coats, penetration macadam Medium Setting (MS or CMS) Used for open-graded asphalt-treated base Slow Setting (SS or CSS) Used for dense-graded asphalt-treated base CIVL 3137 56