presentation; introduction asphalt technology
TRANSCRIPT
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HMA MATERIALS
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Background
Asphalt
Soluble in petroleum
products
Generally a by-product of petroleum
distillation process
Can be naturally
occurring
Tar
Resistant to
petroleum products
Generally by-productof coke (from coal)
production
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Background
First US hot mix asphalt(HMA) constructed in
1870s
Pennsylvania Ave.
Used naturallyoccurring asphalt from
surface of lake on Island
of Trinidad
Two sources Island of Trinadad
Bermudez, Venezuela
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Background
Each lake asphalt source very consistent
Used solubility test to determine source
Insolubles differed substantially between
sources
Demand for paved roads exceeded the supply of
lake asphalts in late 1800s
Led to use of petroleum asphalts
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Petroleum -Based Asphalts
Asphalt is waste product from refinery
processing of crude oil
Sometimes called the bottom of the barrel
Properties depend on:
Refinery operations Composition crude source-dependent
Gasoline
Kerosene
Lt. Gas Oil
Diesel
Motor Oils
Asphalt
Barrel of Crude Oil
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Asphal t Cement Components
Asphaltenes Large, discrete solid inclusions (black)
High viscosity component
Resins Semi-solid or solid at room temperature
Fluid when heated
Brittle when cold
Oils Colorless liquid
Soluble in most solvents
Allows asphalt to flow
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Refinery Operat ion
FIELD STORAGE
PUMPINGSTATION
LIGHT DISTILLATE
HEAVY DISTILLATE
PROCESSUNIT
ASPHALTCEMENTS
FOR PROCESSING INTO
EMULSIFIED AND
CUTBACK ASPHALTS
STILL
AIR
AIRBLOWNASPHALT
STORAGE
TOWERDISTILLATIONREFINERY
RESIDUUM
OR
GAS
PETROLEUM
SAND AND WATER
CONDENSERSAND
COOLERS
TUBEHEATER
MEDIUM DISTILLATE
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Types
Asphalt cements
Generally refinery produced material
Air blown asphalt cements
Cutbacks Asphalt cements cut with petroleum solvents
Emulsions
Mixture of asphalt cement, water, and emulsifying
agent
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Cutbacks
Rapid cure (RC) (Naphtha or Gasoline)
High volatility of solvent
Tack coats, surface treatments
Medium cure (MC) (Kerosene) Moderate volatility
Stockpile patching mix
Slow cure (SC) (Low viscosity oil)
Low volatility
Prime coat, dust control
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Emuls ions
Emulsifier gives surface charge to asphalt dropletssuspended in water medium
Anionic
Negative charge
Alkaline
Good with limestones (positive charge)
Cationic
Positive charge
Acid
Good with silica gravels (negative charge)
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Purchasing of Asphalt Cements
Need to be able to specify desirable
characteristics
Desirable characteristics have evolved
over time and with increasingtechnological advances
Purchasing requires speci f icat ions
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Early Speci f icat ions
Lake Asphalts
Appearance
Solubility in carbon disulfide
Petroleum asphalts (early 1900s)
Consistency
Chewing
Penetration machineMeasure consistency
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Penetrat ion Testing
Sewing machine needle
Specified load, time, temperature
100 g
Initial
Penetration in 0.1 mm
After 5 seconds
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Penetrat ion Speci f icat ion
Five Grades
40 - 50
60 - 70 85 - 100
120 - 150
200 - 300
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Viscosi ty Graded Speci f ications
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Viscosity: the ratio between the applied shear
stress and the rate of shear.
h = t / g
Defini t ion
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Types o f Viscosi ty Tubes
Asphalt Institute TubeZietfuchs Cross-Arm
Tube
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Test ing
Absolute viscosity
U-shaped tube with
timing marks & filled with
asphalt
Placed in 60C bath
Vacuum used to pull
asphalt through tube
Time to pass marks Viscosity in Pa s (Poise)
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Tab le 1 Example
AC 2.5 AC 40
Visc, 60C 250 + 50 4,000 + 800
Visc, 135C 80+ 300+
Penetration 200+ 20+
Visc, 60C
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40
50
60
7085
100
120
150
200300
Penetration Grades
AC 40
AC 20
AC 10
AC 5
AC 2.5
100
50
10
5
Vis
cosity,
60C(
140F)
AR 16000
AR 8000
AR 4000
AR 2000
AR 1000
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Aggregates
Usually refers to a soil that has in some way beenprocessed or sorted.
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Excavat ion
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Crushing
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Transportat ion
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Sizing
Stockpi l ing
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Desired Aggregate Properties
ToughnessSoundness
Deleterious Materials
Gradation
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Soundness
Before After
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Mechan ical Sieve
Individual Sieve Stack of Sieves
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Mechanical Sieve
Stack in
Mechanical
Shaker
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* Uniformly graded- Few points of contact- Poor interlock (shape dependent)
- High permeability
* Well graded- Good interlock
- Low permeability
* Gap graded- Only limited sizes- Good interlock- Low permeability
Types of Gradations
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Aggregate Size Defin i t ions
Nominal Maximum Aggregate
Size
one size larger than the first sieve
to retain more than 10%
MaximumAggregate Size
one size larger than nominal
maximum size
100
10090
72
65
48
36
22
15
9
4
100
9989
72
65
48
36
22
15
9
4
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100
0.075 .3 2.36 4.75 9.5 12.5 19.0
Percent Passing
control point
restr icted zone
max density line
max
size
nom
max
size
Sieve Size (mm) Raised to 0.45 Power
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Quest ions - ?