presentation; introduction asphalt technology

8/13/2019 Presentation; Introduction Asphalt Technology

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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 - ?

presentation; introduction asphalt technology

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