Asphalt Paving Materials Bituminous Materials

Bitumen—also known as asphalt or —is a black, oily, viscous form of , 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% and lesser amounts of , nitrogen, sulfur, and other elements.

CIVL 3137 2 Bituminous Materials

Bituminous Materials

Natural Tar & Petroleum Asphalts Asphalts

(late 1800s)(late 1800s) (early 1900s)

CIVL 3137 3 Natural Asphalt

Rock Asphalt Asphalt 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 . 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 & IN KENTUCKY

CIVL 3137 7 Asphalt

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 (www.gstt.org) Native Asphalt

CIVL 3137 14 La Brea “Tar” Pits

Wilshire Blvd

CIVL 3137 15 , 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 and free carbon, obtained from a variety of organic materials such as , 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 .

CIVL 3137 25 Wood Tar Kiln, Sweden

https://en.wikipedia.org/wiki/Tar CIVL 3137 26

Coal tar is produced by heating coal without oxygen to produce coke and oil gas. Coal tar was used to construct the first surfaced . This is where we get the term “tarmac” or “tar ”. 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 (greater than 500°C) so it represents the residual left over after everything else (gasoline, , diesel, etc.) has boiled off in the distillation process.

CIVL 3137 32 Crude Oil Chemistry

Oils (Hydrocarbons)

Resin-coated

CIVL 3137 33 Crude Oil

Light Crude Heavy Crude

“oils” “oils” “oils” “oils”

Aromatic Saturated Hydrocarbons Hydrocarbons(oils)

CIVL 3137 34 Atmospheric Distillation

Butane & 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

Light Gas OIl Medium Gas OIl Heavy Gas Oil

Topped Crude Heat Bitumen Residuum (Asphalt )

Vaporizes the topped crude without using excessive heat (“cracking”)

CIVL 3137 36 Crude Oil

Gasoline Kerosene 6 Lt. Gas Oil 7 21 33

Hv. Gas Oil 26 14 10 20

28 16 Bitumen 58 Residuum

27 30

Boscan Arabian Nigeria Heavy Light

CIVL 3137 37 Petroleum Asphalt

Petroleum asphalt at room temperature is very stiff. In order to mix it with aggregate to make asphalt , 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-

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)

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 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

Anionic Emulsifier Cationic 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