1. Asphalt and Asphalt Concrete
History
Asphalt and Tar Material
Engineered Asphalt Cements
Hot-mixed asphalt
Cutbacks
Emulsions
Properties of Asphalt

2. History
3500 B.C. natural bitumen used to line reservoirs by the Greeks
First US asphalt in NY and NJ
Automobile drove the ACC industry
The natural bitumen was coal tar with volatile oils. The oils would evaporate to set the asphalt
Sidewalks in Brooklyn (1865) were first major use of asphalt concrete in US. The first pavements were in Newark, NJ (1870).

3. Sources of “Natural” Asphalt Cementè
Natural asphalts are refined by nature
Trinidad Lake asphalt
very hard, mined commercially
Washington, DC 1870’s
Gilsonite in Utah
contains fine sand
Rock asphalt Kentucky, Texas
sandstone impregnated with asphalt
“Tar“ sands
in Canada (Athabasca)
La Brea “tar” pits in California

4. Bitumen and Asphalt
Bitumen: non-volatile hydrocarbon, soluble in carbon disulfide, very complex material structure
Coal tar, asphalt (processed oil residue)
Asphalt (combination of asphaltine, resin, oil)
Asphaltine (C/H>0.8)
Resin (0.8>C/H>0.6)
Oil (C/H < 0.6)
Specific Gravity = 0.95 – 1.05
Tar comes from the destructive distilling of coal, wood, shale to form “pitch” and then adding the distilled non-volitle
Asphaltine provide the body of AC
Resin provide the adhesion and ductility
Oil provides the viscosity and flow
As oils evaporate, AC stiffens.
Resins age by oxidizing (loss of ductility and adhesion)
All properties tend toward pure asphaltine as AC ages.

5. Composition of Asphalt Cementè
Large organic molecules of varying size and polarity
Carbon 80 -
87%
Nitrogen 1%
Hydrogen 9
11%
Sulfur
0.5 7%
Oxygen 2 8%
Heavy metals
0.5%
Heavy metals play important role
Contribute to polarity
Molecular structure very complex
Asphaltenes
largest and most polar
Resins
intermediate, also polar
Oils
smallest, paraffin
like, non
polar
Colloidal model
Asphaltenes surrounded by resins
Oils continuous medium
Asphaltenes
Resins
Oils

6. Refinery Operation Lighter molecules vaporize Asphalt cement remains
FIELD STORAGE TANKS
PUMPING
STATION
LIGHT
DISTILLATE
HEAVY
ASPHALT
CEMENTS
STORAGE
TOWER
DISTILLATION
RESIDUAL
CONDENSERS
AND
COOLERS
TUBE
HEATER
MEDIUM
OIL WELL
SOLVENTS
GASOLENE
JET FUEL
LUBRICANTS
HEATING OIL
Lighter molecules vaporize
Asphalt cement remains
Residual varies in consistency
3 types of petroleum
asphaltic crude (Texas heavy crude)
paraffin crude (Saudi light crude)
Mixed crude

7. Asphalt Characterization
Flash Point: temperature at which a substance will ignite with a open flame
Rolling Thin-Film Oven: indicator of the aging effect of short term high temperatures when producing ACC.
Viscosity: rotational viscometer measures the viscosity at a standard temperature (135C)
Complex Shear Modulus: dynamic shear rheometer
Flexural Creep: bending beam rheometer measure creep stiffness
Tensile Strength

8. 70C to 150C viscous liquid
-20C to 70C viscoelastic solid
< -20C brittle solid

9. Engineered Asphalt Cement
Hot mixed asphalt (pavements)
Viscous semi-solid
Flows for heating into liquid range
Cutback asphalt
Viscous liquid
Cut with oil distillates
Emulsion asphalt
Cut with water
Slow cure (diesel oil), Med. Cure (kerosene), Fast cure (gas or naptha)

10. Emulsions Asphalt Binder Liquefied with Water- è
Water -
reduces viscosity è
Emulsifier gives surface charge to asphalt droplets suspended
in water medium
Anionic
Water
Asphalt
Binder Ÿ
Negative charge Ÿ
Alkaline (Basic) aggregate Ÿ
Good with limestones (positive charge)
Cationic Ÿ
Positive charge Ÿ
Acidic aggregate Ÿ
Good with silica gravels (negative charge) è
Consistency controlled by amount of water è
Stability controlled by choicer of emulsifier è
Environmentally correct

11. Properties of Asphalt Cement
Adhesion: property to connect dissimilar materials
Cohesion: property to connect similar materials
3M scotch tape is adhesive, not cohesive
Silly putty is cohesive, not adhesive
Asphalt is adhesive and cohesive
Adhesion: property to stick to aggregate particles (property to connect dissimilar materials)
Cohesion: ability to stick particles together (property to connect similar materials)

12. Flow properties
Consistency: measure of fluidity at a given temperature
Absolute Viscosity, poises
Kinetic Viscosity, centistokes
Penetration: empirical measure of ease to penetration
Penetration of 1 mm diameter needle.
Abs. Viscosity is measured by drawing a material through a tube with a controlled vacuum.
Kinetic viscosity is determined by using a rotating viscometer.
Penetration is distance a 1mm needle under a constant 100g load penetrates a 25C materia in 5 seconds, expressed in 0.1mm, e.g. 11mm = 110 pen
Examples of viscosity:
Water Poises
Diesel Poises
50 SAE Oil 10 Poises (liquid)
Soft tar 1000 Poises (semi-liquid)
300 pen AC Poises (semi-solid)
15 pen AC 100,000,000 Poises (solid)

13. Performance-Graded Asphalt Binders
Maximum
Temperature (
ºC)
Minimum Temperature (
PG 46 - 34 40 46
PG 52 10 16 22 28
PG 58 - 16 22 28 34 40
PG 64 10
PG 70
PG 76
PG 82
As an example, a PG 64 -
28 is acceptable for use in a
climatic region where the maximum temperature is
64°C and the minimum temperature is -
28°C.

14. Selection of Grading Temperatures- 28 22 16
Given that the minimum measured air temperature for a site is
21°C and
the maximum 7
day average temperature is 73°C, which PG grade should
be used for this site.
Here, use PG 76
22.
Pavement
Air Temperature
Maximum 7
day
(Running Average)

15. Alternative Grading System
Grade
Viscosity
Abs., Poises Kinetic, cStokes
Penetration
Flash Point °C
AC-2.5
250
125
220
163
AC-5
500
175
140
177
AC-10
1000 80
219
AC-20
2000
300 60
232
AC-30
3000
350 50
AC-40
4000
400 40

16. Asphalt and Asphalt Concrete
Aggregates
Properties
Pavements
Mixture Design

17. Asphalt Concrete Aggregates
clean and dry aggregates are necessary for adhesion (no dust, no water)
interlocking nature creates internal friction which is important to the long-term properties of the asphalt concrete.
angular shape aggregates 50-80% with 2 angular faces

18. ACC: Importance of Aggregate
Asphalt cement has no strength at temperatures > 60C
Stability of pavements in hot weather is due to internal friction in the aggregates

19. Asphalt Concrete Mixtures
Mixtures of aggregate and asphalt cement binder
about 95% aggregate by weight
about 75% aggregate by volume
ideally, 3-5% air voids

20. Asphalt Concrete Flexibility Short-term Loadings high binder content
low viscosity binder
Short-term Loadings
elastic properties of binder-aggregate matrix

21. Asphalt Concrete Long-term Durability fluid properties of binder
dry clean aggregates
water causes “stripping”
strong porous angular stone
durable aggregates (LA abrasion)

22. Asphalt Concrete
Workability: Ease in which material is handled and laid and compacted.
poor compaction leads to deformation and the permeability of water and air.
temperature affects workability
Strength
high viscosity binder
crushed stone aggregates (interlock)

23. Pavement Section
ACC Surface
ACC Base
Granular Subbase
Subgrade

24. Asphalt Pavement Distress
Cracking
Traffic Associated Fatigue
Rutting

25. Asphalt Concrete Applications
Roofing,
slurry
composition shingles
Sealants
waterproofing for foundations, etc
electrical insulation

26. Asphalt Concrete Applications
Pavements
Hot Mixed Asphalt Cement
(asphaltine, resin)
Emulsions (repairs, small jobs)
moist or dry aggregates
hot or cold applications
no fuel or solvents
anionic or cationic

27. Asphalt Concrete Applications
Cutbacks (on the way out)
RC - flash point in 27°C !!!
hard base (hot regions)
MC - safer
softer base (cold regions)
SC - “Road Oils”
rural roads, sealants

28. Primary Distress Modes HMA Pavements
Rutting
Rutting
Fatigue Cracking 5 -
15 m
Fatigue Cracking
Moisture Damage?
Thermal Cracking

29. Temperature Regimes where Distress Predominates
Low -
temperature thermal
Plexiglas
Shrinkage cracking
Intermediate -
temperature
Salt Water
Consistency
traffic -
associated fatigue
Taffy
Molasses
High -
temperature
rutting - 25 25 50 75
Approximate Temperature, C