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Construction Methods & Materials II Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter 2019 1 Construction Methods and Materials II Asphalt and Asphalt Mixtures Construction Methods & Materials II 2 Introduction US petroleum consumption: 20 million barrels/day 149 operating refineries in the US Over 600 million barrels/year of asphalt is produced and marketed. About 85 to 90% of this is asphalt for paving.

Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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Page 1: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 1

Construction

Methods and Materials II

Asphalt and Asphalt

Mixtures

Construction Methods & Materials II

2

Introduction

US petroleum consumption:

20 million barrels/day

149 operating refineries in the US

Over 600 million barrels/year of asphalt is produced and marketed.

About 85 to 90% of this is asphalt for paving.

Page 2: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 2

Construction Methods & Materials II

Introduction One barrel of crude

oil equals 42 gallons (or 159 liters).

Typical products from a barrel of crude oil is shown here.

The amount of each product that can be derived from crude vary depending on the crude source.

3Liquefied petroleum gas or liquid petroleum gas (LPG or LP gas), aka propane or butane.

Construction Methods & Materials II

4

Bituminous Materials Topics History

Introduction

Refiners

ExxonMobil—a global supplier

Types of asphalt products

Uses of asphalt

HMA pavement construction

Characterization of asphalt binders

Superpave HMA mix design

Other asphalt uses

Page 3: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 3

Construction Methods & Materials II

History of and Use of Bituminous Materials

Use in Ancient Times

From 6000 B.C. through Columbus voyage

Mastic in statuary, pottery, and ornaments -6000 B.C.

Caulking for ships - 600 B.C.

Embalming purposes - 2500 to 1500 B.C.

Paved streets and constructed walls of bricks set in asphalt - 600 B.C.

Medicinal - 1400 to 600 B.C.

New World - Christopher Columbus caulked the seams of the ship with Trinidad asphalt - 1498

5•Mastic asphalt is a sticky, black and highly viscous liquid.

Construction Methods & Materials II

History of and Use of Bituminous MaterialsUse in Modern Times

Began in 1700's Tar in roofing in Germany - 1730

Seyssel asphalt deposit - marketed for surfacing floors, bridges, sidewalks, and waterproofing - 1790

McAdam develops compacted layered rock design-unbound-1817

Coal tar used in tar-macadam pavement in Gloucestershire-1832

Rock asphalt from Europe used in New York - 1870

Barber Asphalt Paving Co. develops equipment and processes for sheet asphalt paving - 1899

Asphalt produced commercially from petroleum - 1902

Hot mix plants developed - 1910

Mix Designs developed - 1930's6

Page 4: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 4

Construction Methods & Materials II

Terminology

Bitumen

Black or dark-colored cementitious substances

Solid, semisolid, or viscous

Natural or manufactured

High molecular weight (complex) hydrocarbons

Soluble in carbon disulfide

asphalt

tars

pitches7

Construction Methods & Materials II

Terminology

Asphalt Cement - asphalt refined to meet specifications

Asphalt Concrete - mixture of asphalt cement and aggregate

Cutback Asphalt - liquid asphalt - blend of asphalt cement and petroleum solvents

Emulsified Asphalt - liquid asphalt - blend of asphalt cement, water, and emulsifying agent

8

Bitumen Material

Hardness(Ambient Temp.) Source

Asphalt Variable Natural or Fractional Distillation of Petroleum

Tar Liquid or Semi-Liquid

Destructive Distillation of Coal or other Organic Matter

Pitch Hard - Liquefies with Heat

Fractional Distillation of Tar

Coal Tar Hard - Liquefies with Heat

Destructive Distillation of Coal

A suspension of tiny droplets of one liquid in a second liquid.

Page 5: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 5

Construction Methods & Materials II

Tars and Pitches Most tars produced from coal

Coal heated to produce coke

Lighter fractions vaporized

These lighter fractions collected and distilled to create desired grades

Road Tars

Resistant to the dissolving actions of petroleums

Road tar concrete on airfields at refueling points

In emulsions, surface sealant on parking lots

Built-up roofing

Waterproofing of foundations, retaining walls, dams, etc.

9

Construction Methods & Materials II

Natural Asphalt Same material as petroleum

Lighter fractions removed by natural processes

Earliest use of asphalt were from natural deposits

1. Native or Lake Asphalts

Asphalt occurring in nature, open deposits

Up to 65% asphalt

Trinidad, West Indies

Bermudez, Venezuela

La Brea Atar@ pits near Los Angeles

2. Rock Asphalts

Porous rock impregnated with natural asphalt

sandstone

limestone

2 to 20% bitumen

Seyssel asphalts from France

Uvalde, Texas rock asphalt10

Page 6: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 6

Construction Methods & Materials II

11

Natural sources

Trinidad Lake Asphalt

Primary world asphalt supplier 1875 - 1900

Construction Methods & Materials II

12

Natural sources

Gilsonite

Naturally occurring asphalt in Utah

Picture from Asphalt Associates, Ltd.

Gilsonite, also known as asphaltum, is a bitumen-impregnated rock (asphaltite) mainly found in the Uintah Basin of Utah and Colorado. It is a naturally occurring solid hydrocarbon bitumen.

Page 7: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 7

Construction Methods & Materials II

Production of Asphalt from Petroleum

Most asphalts used in construction are from fractional distillation of crude oils in refineries

Common Refinery Products

Straight run gasoline

Naphtha

Kerosene distillate

Diesel fuel

Lubricating oils

Heavy residue

13

Construction Methods & Materials II

Production of Asphalt from Petroleum Asphalts

Come from heavy residue

Second stage distillation completed on heavy residue

vacuum tower fractionation

heavy residue again heated and distilled

Produces

additional lighter oils

asphalts of desired consistencies

Air Blowing Air-blowing modifies asphalt cements for roofing applications

Produces stiffer asphalt that retains that stiffness at higher temperatures

A type of polymerization

14

Page 8: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 8

Construction Methods & Materials II

Asphalt Cement (aka Paving Asphalt)

Asphalt cement is a type of asphalt that is very sticky and highly viscous, specially prepared with the quality and consistency required in the manufacture of asphalt pavements (hot-mix pavements). Asphalt cements are used because

Ability to coat aggregate

Act as a binder between aggregate particles

Water resistance

Typical uses

road construction

roofing applications

roofing shingles

water proofing applications

coatings15

Construction Methods & Materials II

Liquid Asphalts Asphalt cements are stiff at normal temperatures

Softening by heating not feasible in all cases

Liquid asphalts are liquid at normal ambient temperatures

Two Types - both produced from asphalt cement

Cutback Asphalts

Emulsified Asphalts

1. Cutback Asphalts

Asphalt cement recombined with diluent (also called solvent, distillate, or cutter stock)

Diluent evaporates leaving original asphalt cement

Adding sufficient diluent produces liquid asphalt

Type of diluent determines how rapidly it will evaporate

16

Page 9: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 9

Construction Methods & Materials II

Liquid Asphalts2. Emulsified Asphalts

Asphalt cements mixed with emulsifying agent and water in colloidal mill

Water is continuous phase (at least 25%)

Asphalt is the discontinuous phase

Emulsifying agent places electrical charge around each droplet of asphalt

negative (anionic)

positive (cationic)

Since like electrical charges repel, droplets stay suspended in continuous water phase

Stable situation until disrupted by

mixing with aggregates

evaporation of water17

Construction Methods & Materials II

ExxonMobil Complex—Baytown, Texas

Globally produces 6 million tons (or about 30 million barrels) of asphalt per year which is marketed in 30 countries.

Only 19 of ExxonMobil’s 49 refineries can produce asphalt.

18

Page 10: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 10

Construction Methods & Materials II

ExxonMobil Complex—Baytown, Texas

19

Construction Methods & Materials II

ExxonMobil Complex—Baytown, Texas

20

Page 11: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 11

Construction Methods & Materials II

ExxonMobil Tankers Offloading Crude —Baytown, Texas

21

Construction Methods & Materials II

22

Types of asphalt products

Distillation of crude oil

Asphalt cements

Cutback asphalts

Slow-curing

Medium-curing

Rapid-curing

Emulsified asphalts

Less used today due to environmental impacts.

Page 12: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 12

Construction Methods & Materials II

Uses of asphalt

The primary one of interest for CM 323 is hot mix asphalt (or hot mix asphalt concrete).

WSDOT pavements (total of 18,000 lane-miles)

HMA 60%

Bituminous surface treatment (BST) 27%

PCC 13%

23

Construction Methods & Materials II

24

HMA pavement construction

Pavement cross sections

Overview of HMA plant operations

Trucks

Pickup machines

Laydown machines

Page 13: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 13

Construction Methods & Materials II

Bituminous Surface Treatment

HMA

25

Pavement cross sections

HMA Bituminous Surface Treatment

12-ft

0.5 to 1-in.

Thickness ranges from 2 in. to over 1 ft.

Construction Methods & Materials II

HMA and Asphalt Binders

26

Page 14: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 14

Construction Methods & Materials II

Bituminous Surface Treatment (BST)

(aka seal coat or chip seal)

Construction Methods & Materials II

Production of HMA (plant operations)

28

Page 15: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 15

Construction Methods & Materials II

29

Plant—aggregate conveyors

Construction Methods & Materials II

30

Plant—mixing drum

Page 16: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 16

Construction Methods & Materials II

31

Plant—mixing drum

Construction Methods & Materials II

32

Plant--burner

Page 17: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 17

Construction Methods & Materials II

33

Plant—aggregate storage bins

Construction Methods & Materials II

34

Plant—adding RAP to drum and RAP stockpile

RAP: Recycled Asphalt Pavement

Page 18: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 18

Construction Methods & Materials II

35

Plant—storage silos

Construction Methods & Materials II

36

Plant—control house

Page 19: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 19

Construction Methods & Materials II

37

Trucks—Flowboy

Construction Methods & Materials II

38

Trucks—Belly Dump

Page 20: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 20

Construction Methods & Materials II

39

Remixing—Blaw-Knox MC-30

Construction Methods & Materials II

40

Remixing—Roadtec Shuttle Buggy

Photo courtesy of Roadtec

Page 21: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 21

Construction Methods & Materials II

41

Remixing—Roadtec Shuttle Buggy

Construction Methods & Materials II

42

Remixing—Roadtec Shuttle Buggy

Page 22: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 22

Construction Methods & Materials II

43

Infrared Image—End Dump

Route: SR-203

Section:

King/Snohomish

Line to SR-2

Binder: PG 64-22

Mix: Class A

Haul Time: 30

minutes

Haul Length: 18

miles

Plant Temp: 290°F

Mat Temp: 255°F

Comments:

Thermal

differential of 140

degrees between

crust and internal

mix.

290.5

148.9

>302.0°F

<68.0°F

80 .0

100 .0

120 .0

140.0

160 .0

180 .0

200.0

220.0

240.0

260.0

280.0

300.0

Construction Methods & Materials II

Trucks—end dump into paving machine

44

Page 23: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 23

Construction Methods & Materials II

Trucks—end dump into paving machine

45

Construction Methods & Materials II

Infrared Image—End Dump

46

Route: SR-203

Section: King/Snohomish Line to

SR-2

Binder: PG 64-22

Mix: Class A

Haul Time: 30 minutes

Haul Length: 18 miles

Plant Temp: 290°F

Mat Temp: 255°F

Comments: Temperatures and

corresponding densities.

94.6%

201.2

89.8%

154.392.7%

176.693.7%

194.992.4%

204.387.8%

206.0

*>237.6°F

*<68.0°F

80 .0

100 .0

120 .0

140.0

160 .0

180 .0

200.0

220.0

Page 24: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 24

Construction Methods & Materials II

47

Finish roller on I-90 near Vantage

Construction

Methods and Materials II

HMA PLACEMENT

Hauling

Placement

Compaction

48

Page 25: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 25

Construction Methods & Materials II

49

Different types of trucks are used

Construction Methods & Materials II

50

Self Propelled Paver

Page 26: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 26

Construction Methods & Materials II

51

Self Propelled Paving Machine

THE BASIC PRINCIPLE HAS NOT CHANGED MUCH SINCE THE 1930’s

Construction Methods & Materials II

52

HMA Flow

Self Propelled Paving Machine

Page 27: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 27

Construction Methods & Materials II

53

Compaction

GOOD COMPACTION LEADS TO GOOD PERFORMANCE

Compaction is the single most important factor that affects the ultimate performance of an HMA pavement.

Construction Methods & Materials II

Reason For Compaction

To prevent further compaction

To provide shear strength or resistance to rutting

To ensure the mixture is waterproof

To prevent excessive oxidation of the asphalt binder

54

Page 28: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 28

Construction Methods & Materials II

55

Temperature is critical

Construction Methods & Materials II

One of the most important factors is the mix temperature

Too cold and the mix cannot be compacted

Too hot and the mix will not support the rollers

56

Temperature is critical

Page 29: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 29

Construction Methods & Materials II

57

Vibratory Roller

Construction Methods & Materials II

Vibratory Roller Vibratory rollers come in a variety of configurations.

Single drum and double drum.

These rollers can be operated in any one of three modes:

static (with the vibrators off),

with one drum vibrating and one static, and

with both drums vibrating.

These rollers provide two types of compactive force to the HMA - static force and dynamic (impact) force.

The static force is caused by the weight of the roller and frame.

The dynamic force is caused by the impact produced by a rotating eccentric weight located inside the drum or drums. As the eccentric weight rotates about the shaft inside the drum, a dynamic force is produced.

58

Page 30: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 30

Construction Methods & Materials II

59

Pnuematic Roller

Construction Methods & Materials II

Pnuematic Roller

Most pneumatic rollers are operated as intermediate rollers - behind a vibratory or static steel wheel breakdown roller and in front of a static wheel finish roller.

The compactive force is a function of the wheel load of the machine, the tire pressure, the tire design and the depth of penetration of the tires into the mix.

The tire pressures range from 60 to 120 psi and the minimum weight is 15 tons. For a tender mix a lower tire pressure should be used. For a stiff mix a higher tire pressure should be used.

60

Page 31: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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Construction Methods & Materials II

61

Steel Wheeled Roller

Steel wheel rollers range from 3 to 14 tons.

They can either be three wheel here or tandem.

Construction Methods & Materials II

62

Extracting A Core

Cores are taken for density determination and thickness. They are usually cut to obtain a sample of the layer being

placed. The bulk specific gravity of the core is determined and

using that with the maximum specific gravity it is possible to determine the percent compaction.

Page 32: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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63

Cost of HMA

Construction Methods & Materials II

64

Page 33: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

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Professor Kamran M. Nemati

Winter Quarter 2019 33

Construction Methods & Materials II

Primary Reference Information

Pavement Interactive Asphalt

(http://www.pavementinteractive.org/article/materialsasphalt/)

Asphalt tests (http://www.pavementinteractive.org/category/testing/asphalt-tests/?show=all)

Superpave mix design (http://www.pavementinteractive.org/category/testing/asphalt-tests/?show=all)

Chip seals or BSTs (http://www.pavementinteractive.org/article/bituminous-surface-treatments/)

65

Construction Methods & Materials II

66

Characterization of asphalt binders

Prior to PG (Performance Graded) grades, asphalt binder specifications typically were based on measurements of viscosity, penetration, ductility, and softening point temperature.

Performance Graded (PG) Binder (a.k.a. Asphalt Cement)

Penetration Measurement

Page 34: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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Winter Quarter 2019 34

Construction Methods & Materials II

67

Characterization of asphalt binders

Softening Point TemperatureDuctility Test

Viscosity TestViscosity denotes the fluid property of bituminous material and it is a measure of resistance to flow.

Construction Methods & Materials II

Manufactured sources

Crude oil

Crude oil surpassed natural sources in 1907

Atmospheric

DistillationVacuum

Distillation

Vacuum

Residual

Conversion Unit

Asphalt

CrudeOil

PrincipalRefineryProducts

Lube oilsFuel oilsSolventsWaxesGrease

GasolineJet FuelDieselKeroseneChemicals

68

Page 35: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 35

Construction Methods & Materials II

Crude oil make-up

26

28

30

7

10

16

14

20

21

33

58

27

1

6 3

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Boscan Venezuela Arabian Heavy Nigerian Light

Crude Oil Type

Perc

en

t

Gasoline

Kerosene

Light Gas Oil

Heavy Gas Oil

Bitumen Residuals

69

Construction Methods & Materials II

Crude oil

Utah West Texas North Sea

Sudan Illinois

Source: http://www.chevron.com 70

Page 36: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 36

Construction Methods & Materials II

71

Asphalt characteristics

Thermoplastic material

Properties change with temperature

Important characteristics

High temperature: construction workability

Medium temperature: deformation resistance

Low temperature: thermal cracking resistance

Construction Methods & Materials II

72

Low Temp Test

Range

Middle Temp Test

Range

High Temp Test

Range

PG Test Temperatures

The properties of asphalt are susceptible to change as temperature changes.

Page 37: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 37

Construction Methods & Materials II

Viscosity

Quantity that describes a fluid resistance to flow.

There exist several different test methods for measuring viscosity

73

Construction Methods & Materials II

What is a Poise?

74

It is a measure of viscosity.

Units: dyne-second/cm2

A dyne is 10-5 Newtons.

Named after a French physician, Jean Louis Poiseuille (1799-1869).

A commonly used measure is centipoises (or 1/100 P).

1 Pa·s = 1,000 cP or

1 Poise = 100 cP = 0.1 Pa·s

And centistokes = centipoises/specific gravity

Page 38: Asphalt and Asphalt Mixtures - University of Washingtoncourses.washington.edu/cm323/asphalt.pdf · 2019-02-28 · Asphalt and Asphalt Mixtures Professor Kamran M. Nemati Winter Quarter

Construction Methods & Materials II

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Construction Methods & Materials II

75

A Sample of Viscosities in cP

Material Viscosity (cP)

PG Binders @ 135°C(AASHTO M320 and ASTM D4402)

3,000 max

Venezuelan Orinoco heavy oil @ 53°C

1,500—3,000

Motor oil @ SAE 10 @ 20°C 65

Motor oil @ SAE 30 @ 20°C 150—200

Motor oil @ SAE 40 @ 20°C 320

Bunker C Fuel Oil

(ocean vessels but often quoted in centistokes)

Gasoline 0.6

Water 1

Construction Methods & Materials II

76

Material Viscosity (cP)

Olive Oil @ 25°C 80

Peanut Butter 250,000

Tar @ 20°C 30,000,000

Blood @ 20°C 3 to 4

Honey @ 20°C 10,000

Ketchup @ 25°C 50,000 to 100,000

A Sample of Viscosities in cP

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 39

Construction Methods & Materials II

77

Asphalt grading

Grading

Shorthand way of describing asphalt physical properties

Performance Grading (PG) System

Specifications account for:

Local environment

Traffic loading (somewhat)

WSDOT asphalt binder grading in accordance with AASHTO M320 (or ASTM D 6373)

Construction Methods & Materials II

ASTM D6373

78

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Construction Methods & Materials II

79

PG System

Nomenclature

PG 64-22

Performance grading

system

Expected average 7-day maximum

pavement temperature = 64°C

Expected minimum

pavement temperature =

- 22°C

Construction Methods & Materials II

80

PG Grades

Temperatures listed in Centigrade

Increments of 6°C

PG 46-34

PG 46-40

PG 46-46

PG 52-10

PG 52-16

PG 52-22

PG 52-28

PG 52-34

PG 52-40

PG 52-46

PG 58-16

PG 58-22

PG 58-28

PG 58-34

PG 58-40

PG 64-10

PG 64-16

PG 64-22

PG 64-28

PG 64-34

PG 64-40

PG 70-10

PG 70-16

PG 70-22

PG 70-28

PG 70-34

PG 70-40

PG 76-10

PG 76-16

PG 76-22

PG 76-28

PG 76-34

PG 82-10

PG 82-16

PG 82-22

PG 82-28

PG 82-34

Cold climate Hot climate

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 41

Construction Methods & Materials II

Washington Base PG Binders

PG 64-22

PG 64-28

81

Construction Methods & Materials II

82

California Base PG Binders

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 42

Construction Methods & Materials II

83

PG Binder Grade Determination

Must account for:

Expected traffic loading

Expected traffic speed

And…WSDOT uses 4 types of HMA mixes which are based on nominal maximum aggregate size (NMAS): 3/8-inch, ½-inch, ¾-inch, and 1-inch.

Construction Methods & Materials II

84

PG Binder Grade Determination

Base PG grades with no adjustment for traffic speed or ESAL level Western Washington: PG 64-22

Eastern Washington: PG 64-28

Adjustment for traffic speed Standing (0 to 10 mph): Increase PG high temperature by 2 grades (12°C)

Slow (10 to 45 mph): Increase PG high temperature by 1 grade (6°C)

Free flow (45+ mph): No adjustment

Adjustment for traffic loading (20 year basis) 10,000,000 ESALs: No adjustment

10,000,000 to 30,000,000 ESALs: Consider an increase in the PG high temperature by 1 grade (6°C)

30,000,000 ESALs: Increase PG high temperature by 1 grade (6°C)

Maximum PG high temperature: The maximum increase in the PG high temperature for any combination of conditions will not exceed a 2 grade increase (or 12°C) over the base PG grade.

Source: WSDOT Pavement Policy, June 2011

ESAL: Equivalent Single Axle Load

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 43

Construction Methods & Materials II

85

PG Specification Table

Construction Methods & Materials II

86

PG Table

Rutting

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Asphalt and Asphalt Mixtures

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Construction Methods & Materials II

87

PG Table

Fatigue Cracking

Construction Methods & Materials II

88

PG Table

Low Temperature Cracking

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Asphalt and Asphalt Mixtures

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Construction Methods & Materials II

89

Summary

Asphalt description

Asphalt sources

Asphalt characteristics

Temperature susceptibility

Binder grading

Performance Grading (PG) system

Construction

Methods and Materials II

90

Mix Design

Asphalt and Asphalt Mixtures

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Asphalt and Asphalt Mixtures

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Construction Methods & Materials II

91

Photos fromChina by Yiming

Construction Methods & Materials II

92

Bituminous Materials Topics

Introduction

Refiners

US Oil and Refining—a producer of asphalt binders

ExxonMobil—a global supplier

Types of asphalt products

Uses of asphalt

HMA pavement construction

Characterization of asphalt binders

Superpave HMA mix design

Other asphalt uses

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Construction Methods & Materials II

93

Superpave HMA mix design

Hot mix asphalt (HMA) description

HMA mixture design

Methods

Volumetrics

Job mix formula

Example

Construction Methods & Materials II

Hot Mix Asphalt (HMA)

94

Distinguished by: Materials (asphalt binder and

aggregate)

Mix design methods

Elevated mixing temperature

Other names: Asphalt concrete (AC)

Blacktop

Bitumen

Bituminous concrete

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 48

Construction Methods & Materials II

HMA Description (dense graded)

Construction Methods & Materials II

HMA Description

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Winter Quarter 2019 49

Construction Methods & Materials II

HMA Description

Construction Methods & Materials II

HMA Description

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Construction Methods & Materials II

99

HMA Description

Construction Methods & Materials II

Types of HMA

(VMA = voids in the mineral aggregate)

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Construction Methods & Materials II

101

This is the type of HMA you mostly see

in use in WA.

The best performing type of HMA as a surface (wearing)

course.

Open graded mixes great for safety but quickly damaged by studded tires and

chains.

Construction Methods & Materials II

Hot Mix Asphalt

Described by:

Maximum aggregate size

Aggregate gradation

Asphalt binder

Asphalt binder content

Section 1

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Asphalt and Asphalt Mixtures

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Construction Methods & Materials II

Maximum Aggregate Size

Largest aggregate “diameter” as defined by:

Maximum SizeThe smallest sieve through which 100 percent of the aggregate sample particles pass

Nominal Maximum SizeThe largest sieve that retains some of the aggregate particles but generally not more than 10 percent by weight

103

Construction Methods & Materials II

Gradation

Dense graded

Most common

Gap graded

Stone matrix asphalt (SMA)

Open graded

Used as a surface course in many areas

Uniformly graded

Not used as a construction material

104

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Professor Kamran M. Nemati

Winter Quarter 2019 53

Construction Methods & Materials II

90105

Construction Methods & Materials II

106 106

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Construction Methods & Materials II

Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 54

Construction Methods & Materials II

Asphalt Binder

Choose asphalt binder grade

Select a grade based on:

Design pavement high temperature

Design pavement low temperature

Adjust based on reliability

Adjust based on traffic speed and loading

Add modifiers to achieve certain properties

107

Construction Methods & Materials II

Asphalt Binder Content

Ratio of asphalt binder to aggregate

Determining this is a key component of mix design

Typical binder contents

Usually expressed as a percentage by weight of total mixture

Dense graded HMA = 4.5 to 6.0%

SMA = 6.0 to 8.0%

108

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

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Construction

Methods and Materials II

Superpave Mix DesignProcedure

Construction Methods & Materials II

Superpave Asphalt Pavement

110

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 56

Construction Methods & Materials II

Superpave History

Under the Strategic Highway Research Program (SHRP), an initiative was undertaken to improve materials selection and mixture design by developing:

1. A new mix design method that accounts for traffic loading and environmental conditions.

2. A new method of asphalt binder evaluation.

3. New methods of mixture analysis.

When SHRP was completed in 1993 it introduced these three developments and called them the Superior Performing Asphalt Pavement System (Superpave).

Although the new methods of mixture performance testing have not yet been established, the mix design method is well-established.

111

Construction Methods & Materials II

Superpave Procedure

The Superpave mix design method consists of 7 basic steps:

1. Aggregate selection.

2. Asphalt binder selection.

3. Sample preparation (including compaction).

4. Performance Tests.

5. Density and voids calculations.

6. Optimum asphalt binder content selection.

7. Moisture susceptibility evaluation.

112

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Construction Methods & Materials II

113

Asphalt-Aggregate Ratio

Mix Design = determining this ratio

Procedure:

Select aggregate gradation

Select asphalt binder

Make samples

Test samples for key parameters

Test results predict field performance

Construction Methods & Materials II

115

Concepts

We design volume but measure mass

Specific gravity is important Converts mass to volume

Constituent

Typical Values

By Total Volume By Total Mix Weight

Air 4% 0%

Asphalt 10% 5%

(Range 4% to 6%)

Aggregate 86% 95%

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Construction Methods & Materials II

116

Variables

Aggregate

Asphalt binder

Ratio of aggregate to asphalt binder

Construction Methods & Materials II

117

Goals

Stability (deformation resistance)

Durability

Fatigue resistance

Ductility (low temp. cracking resistance)

Moisture damage resistance

Skid resistance

Workability

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

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Construction Methods & Materials II

Select Aggregate

Must meet:

Consensus requirements

Source properties

118

Construction Methods & Materials II

Select Asphalt Binder

Almost always done to local standard as illustrated by WSDOT criteria

Easier to follow in specifications

Easier for suppliers

119

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Construction Methods & Materials II

Select Aggregate Gradation

120

Source: WSDOT SS, 9-03.8(6)

Construction Methods & Materials II

Design Aggregate Structure

Not many formal procedures to do this

Typical Superpave aggregate structures create quarry waste

121

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 61

Construction Methods & Materials II

Select Asphalt Binder Content

Level of sample compaction is critical

Bleeding Raveling122

Construction Methods & Materials II

First, define VMA and VFA

VMA: % of total volume in a compacted HMA mix due to

1) air voids and

2) the volume of the binder not absorbed into the aggregate (i.e., the space between the aggregate particles).

VFA: % of VMA filled with asphalt binder.

123

VMA: Voids in the Mineral AggregateVFA: Voids Filled with Asphalt

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Construction Methods & Materials II

VMA: Voids in the Mineral AggregateVFA: Voids Filled with Asphalt 124

Construction Methods & Materials II

125

VMA: Voids in the Mineral Aggregate

VFA: Voids Filled with Asphalt

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 63

Construction Methods & Materials II

Conduct Performance Tests

There are none for Superpave right now

Agencies typically use

Moisture susceptibility test

Laboratory wheel tracking devices

126

Construction Methods & Materials II

Important Volumetric Properties

Tests run on compacted samples Mixture specific gravity (Gmb)

Test run on loose mix (uncompacted) Theoretical maximum specific gravity (Gmm)

Often called “Theoretical maximum density” Often called “Rice density”

Calculated volumes (based on above tests) Air voids (Va) Voids in the mineral aggregate (VMA) Voids filled with asphalt (VFA)

127

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Construction Methods & Materials II

1. HMA Bulk Specific Gravity (Gmb) – Ratio of the weight of a unit volume of compacted HMA mixture to the weight of an equal volume of water (includes permeable voids as part of the volume).

2. HMA Maximum Theoretical Specific Gravity (Gmm) – Ratio of the weight of a unit volume of uncompacted HMA mixture to the weight of an equal volume of water (includes permeable voids as part of the volume). This value is often referred to as the “Rice” gravity.

3. Voids in the Total Mix (VTM) – Also known as air voids. Ratio of the volume of voids in a compacted mixture to the total compacted mixture volume.

4. Voids in the Mineral Aggregate (VMA) – Volume of voids and effective binder in a compacted HMA mixture.

5. Voids Filled with Asphalt (VFA) – The percentage of VMA that is filled with binder.

6. Total Binder Content (Pb) – Total amount of binder in an HMA mixture expressed as a percent of the total mixture weight. It can also be expressed as percent of aggregate weight.

7. Percent Binder Absorbed (Pba) – Amount of binder absorbed by the aggregate in an HMA mixture. It is usually expressed as a percentage of the total aggregate weight.

8. Effective Binder Content (Pbe) – Total binder content less the absorbed binder content.

9. Bulk Density – Terminology loosely used in the industry. To obtain the bulk density, multiply the Gmb by 62.4 pcf.

128

Hot-Mix Asphalt Definitions

Construction Methods & Materials II

Hot-Mix Asphalt - Equations

129

The pycnometer (from the Greek puknos, meaning "density", also called pycnometer or specific gravity bottle),

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Construction Methods & Materials II

Hot-Mix Asphalt - Equations

130

Ps = % aggregate by weight of mix

Gsb = aggregate specific gravity

Gmb = mix specific gravity,

Gmm = theoretical maximum specific gravity

(zero air voids)

Construction Methods & Materials II

Hot-Mix Asphalt - Equations

131

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Construction Methods & Materials II

Equations Air voids

VMA

VFA

100

mm

mbmm

aG

GGV

100

11

sb

bmb

G

PGVMA

sb

smb

G

PGVMA 100

VMA

VVMAVFA a

100T

V

aV

VV

Pb = % asphalt binder by weight of mix, Ps = % aggregate by

weight of mix

Gsb = aggregate specific gravity, Gmb = mix specific gravity,

Gmm = theoretical maximum specific gravity (zero air voids).132

Construction Methods & Materials II

Develop Job Mix Formula (JMF)

End result of mixture design

A specification (along with tolerances) used for plant production of HMA

Cannot be significantly altered without another mix design

133

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Construction Methods & Materials II

Job Mix Formula (JMF)

134

Construction Methods & Materials II

135

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Construction Methods & Materials II

136

Construction Methods & Materials II

137

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Construction Methods & Materials II

138

3 Basic Lab Compaction Methods

Marshall Method

Hveem Method

Superpave Method

All use the same basic procedure

This one exists in CM 323 lab

Most widely used today

No longer used—RIP

Construction Methods & Materials II

Prepare Trial Blends

Goal: usually about 4% air voids (why 4%?)

Achieves most objectives satisfactorily

Adding Asphalt Binder Pouring out the mix

139

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Construction Methods & Materials II

Compact Samples

Simulates field compaction by rollers

Simulation is fair to poor

Marshall Method140

Construction Methods & Materials II

Compact Samples

Simulates field compaction by rollers

Simulation is fair to poor

Superpave MethodHveem Method 141

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Construction Methods & Materials II

142

Compact Samples

Height2.5 inches

Diameter4 inches

Marshall & HveemSuperpave

Height4.5 inches

Diameter6 inches

Construction Methods & Materials II

Test Samples

Measure volume properties (volumetrics)

Containers Used to Agitate and Draw a Vacuum on Submerged TMD Samples

TMD: Theoretical Mass Density 143

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Construction Methods & Materials II

Predict how they will perform in the field

Marshall Stability and Flow Test

144

Test Samples

Construction Methods & Materials II

Air voids = Va = VV/VT = (Gmm – Gmb)/Gmm = (2.513 –

2.371)/2.513 = 0.0565 or 5.6%

VMA = 1 – (Gmb(1 – Pb)/Gsb) = 1 – (2.371(1 - 0.049)/2.691)

= 0.162 = 16.2%

VFA = (VMA – Va)/VMA = (0.162 – 0.056)/0.162 = 0.654 =

65.4%

145

Example AGiven:

Bulk specific gravity = 2.371 (Gmb)

Theoretical maximum specific gravity = 2.513 (Gmm)

Aggregate specific gravity = 2.691 (Gsb)

Asphalt content = 4.9% (Pb)

Find air voids, VMA and VFA.

VMA: Voids in the Mineral AggregateVFA: Voids Filled with Asphalt

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146

Example BAn HMA pavement was placed 6 months ago and is already

showing signs of rutting. Several cores were taken from the

pavement in question and the following values were

obtained from laboratory tests:

Asphalt content by ignition oven: 5.9% (Pb)

Theoretical maximum specific gravity: 2.567 (Gmm)

Bulk specific gravities on 3 cores: 2.498, 2.501, 2.490

Aggregate specific gravity = 2.690 (Gsb)

The job mix formula called for:

Asphalt content = 5.6 % ± 0.3%

VMA = must be > 14.0%

VFA = between 65% and 75%

Construction Methods & Materials II

Example B (continued)Pb: 5.9%

Gmm: 2.567

Gmb: 2.498, 2.501, 2.490

Gsb = 2.690

Job mix formula: Asphalt content = 5.6% ± 0.3%

VMA = must be > 14.0%

VFA = between 65% and 75%

Air voids = VV/VT = (Gmm – Gmb)/Gmm = (2.567 – 2.498)/2.567 = 0.0269 or

2.7% (others are 2.6% and 3.0%)

VMA = 1 – (Gmb(1 – Pb)/Gsb) = 1 – (2.498(1 - 0.059)/2.690) = 0.1262 =

12.6% (others are 12.5% and 12.9%)

VFA = (VMA – Va)/VMA = (0.1262 – 0.0269)/0.1262 = 0.7868 = 78.7%

(others are 79.5% and 76.7%)

147

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Construction Methods & Materials II

Superpave Mix Design in the Pavement Interactive

Refer to the article “Superpave Mix Design” in the Pavement Interactive Webpage.

http://www.pavementinteractive.org/article/superpave-mix-design/

148

Construction Methods & Materials II

Superpave Mix Design in the Pavement Interactive

149

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Construction

Methods and Materials II

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Asphalt and Asphalt

Mixtures

Other Uses

Construction Methods & Materials II

Latest paving costs for HMA

Washington Region Urban Rural

Western WA $270,000 lane-mile $207,000 lane-mile

Eastern WA $196,000 lane-mile $165,000 lane-mile

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Assumes a HMA overlay 45 mm thick along with traffic control, 12 ft. lane + shoulder, safety and drainage (12%), mobilization (6%), tax (8%), engineering and contingencies (19%), preliminary engineering (10%).

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Asphalt and Asphalt Mixtures

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Brief List

Mixtures

Cutbacks

Emulsions

Uses

Bituminous surface treatments

Fog Seals

Slurry seals

Tack coats

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Cutbacks

Asphalt cement dissolved in volatile solvent

Typically kerosene or naptha (gasoline)

Upon application, solvent evaporates

85% Asphalt

15% Solvent

TypicalConstituents

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 77

Construction Methods & Materials II

Cutbacks 3 basic types based on volatility of

solvent Rapid Curing (RC): 4 – 8 hours to cure

Medium Curing (MC): 12 – 24 hours to cure

Slow Curing (SC): 48 – 60 hours to cure

Type Components

Percent of Component by Grade

30 70 250 800 3000

RC Asphalt cement 65 75 83 87

Solvent (gasoline, naphtha) 35 25 17 13

MC Asphalt cement 54 64 74 82 86

Solvent (kerosene) 46 36 26 18 14

SC Asphalt cement 50 60 70 80

Solvent (fuel oil) 50 40 30 20

Viscosity

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Emulsion

Asphalt cement emulsified in water Emulsifying agent is essentially soap

Upon application to a surface (pavement), the water evaporates

65% Asphalt

35% Water

TypicalConstituents

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 78

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Emulsions

4 types based on speed of setting (coalescing) Rapid Set (RS): 1 to 5 minutes

Medium Set (MS): 5 to 30 minutes

Slow Set (SS): 20 minutes to several hours

High float (HF): less drain-down (e.g., HFMS-1)

Asphalt globules can have + or – surface charges Anionic: net negative surface charge (RS, MS, SS)

Cationic: net positive surface charge (CRS, CMS, CSS)

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Emulsions

Viscosity grades

1 = low viscosity

2 = high viscosity

Base asphalt

“h” = harder residue (e.g., RS-1h)

“s” = soft residue (e.g., HFMS-2s)

CMS-2h RS-1

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Uses

Bituminous surface treatments (chip seals) CRS-2, RS-2

Fog seals Diluted with water (water:emulsion = 3:1 to 5:1)

MS-1, SS-1, SS-1h, CSS-1, CSS-1h

Slurry seals CSS-1, CSS-1h, SS-1, SS-1h

Tack coat Diluted with water (water:emulsion = 3:1 to 5:1)

SS-1, SS-1h, CSS-1, CSS-1h

Construction Methods & Materials II

Chip Seal

Chip seal is a pavement surface treatment that combines one or more layer(s) of asphalt with one or more layer(s) of fine aggregate.

In the United States, chip seals are typically used on rural roads carrying lower traffic volumes, and the process is often referred to as "asphaltic surface treatment“.

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Winter Quarter 2019 80

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160Photo courtesy of MnDOT

Chip Seal

Construction Methods & Materials II

161Photo courtesy of MnDOT

Chip Seal

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Chip Seal

Construction Methods & Materials II

Fog Seal

A fog seal is a light application of a diluted slow-setting asphalt emulsion to the surface of an aged (oxidized) pavement surface.

Fog seals are low-cost and are used to restore flexibility to an existing HMA pavement surface.

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164Fog Seal

Construction Methods & Materials II

Slurry Seal

A slurry seal is the application of a mixture of water, asphalt emulsion, aggregate (very small crushed rock), and additives to an existing asphalt pavement surface.

A slurry seal is similar to a fog seal except the slurry seal has aggregates as part of the mixture.

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Slurry Seal

Photo courtesy of WSDOT

Construction Methods & Materials II

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Slurry Seal

Photo courtesy of WSDOT

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Asphalt and Asphalt Mixtures

Professor Kamran M. Nemati

Winter Quarter 2019 84

Construction Methods & Materials II

What is a “Tack Coat?”

A tack coat is sprayed on the surface of an existing asphalt or concrete pavement by a distributor truck immediately prior to placing an overlay.

The goal is to achieve uniform coverage over the entire surface to be paved.

Once the tack coat is in place it should be given time to cure and become tacky. Normally this would only require a few minutes.

Traffic should NOT be allowed on a tack coat, to avoid getting dust and dirt on the surface.

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Construction Methods & Materials II

169Tack Coat Photo courtesy of WSDOT

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170Tack Coat Photo courtesy of WSDOT

Construction Methods & Materials II

171Tack Coat Photo courtesy of WSDOT

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172Tack Coat Photo courtesy of WSDOT

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Methods and Materials II

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Asphalt and Asphalt

Mixtures

Asphalt Pavement

Deterioration

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 87

Construction Methods & Materials II

Deterioration of Asphalt Pavement

Asphalt is one of the most durable building components.

The life of asphalt pavement can be cut short due to poor installation, or over exposure to the elements without proper asphalt pavement maintenance.

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Construction Methods & Materials II

Deterioration of Asphalt Pavement

Significant asphalt deterioration can begin to take place after the first two years. Around this time, asphalt starts to turn gray and begins cracking.

Water seeps into the cracks, freezes, and thaws during the yearly cycle, causing larger cracks.

The liquid asphalt binder starts to lose it’s water-resistance properties, and this is how water is able to penetrate the asphalt, causing it a great deal of wear and tear.

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Professor Kamran M. Nemati

Winter Quarter 2019 88

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Deterioration of Asphalt Pavement

The water works down into the sub-surface and softens the base. The pavement begins to give way and buckles under the heavy loads.

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Construction Methods & Materials II

Deterioration of Asphalt Pavement

Pavement begins to separate and break up. Potholes are the result. Alligatoring spreads, asphalt mat looses all flexibility and dries out. Total structural failure results.

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Winter Quarter 2019 89

Construction Methods & Materials II

Crocodile or Alligator Cracking Crocodile cracking (aka fatigue or alligator

cracking), is a common type of distress in asphalt pavement.

Crocodile cracking is characterized by interconnecting or interlaced cracking in the asphalt layer resembling the hide of a crocodile.

Cell sizes can vary in size up to 12 inches across, but are typically less than 6 inches across.

Crocodile cracking is generally a loading failure. It is often a sign of sub-base failure, poor drainage, or repeated over-loadings.

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Construction Methods & Materials II

Crocodile or Alligator Cracking

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Rutting Surface depression in the wheelpath.

Pavement uplift (shearing) may occur along the sides of the rut.

There are two basic types of rutting:

Mix rutting

Subgrade rutting

Mix rutting occurs when the subgrade does not rut yet the pavement surface exhibits wheelpath depressions as a result of compaction/mix design problems.

Subgrade rutting occurs when the subgrade exhibits wheelpath depressions due to loading.

In this case, the pavement settles into the subgrade ruts causing surface depressions in the wheelpath.

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Construction Methods & Materials II

Rutting

Severe Mix Rutting

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Rutting in outside wheelpathdue to subgrade rutting

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Rutting – Possible Causes Permanent deformation in any of a pavement’s layers or

subgrade usually caused by consolidation or lateral movement of the materials due to traffic loading.

Specific causes of rutting can be:

Insufficient compaction of HMA layers during construction. If it is not compacted enough initially, HMA pavement may continue to densify under traffic loads.

Subgrade rutting (e.g., as a result of inadequate pavement structure)

Improper mix design or manufacture (e.g., excessively high asphalt content, excessive mineral filler, insufficient amount of angular aggregate particles)

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Construction Methods & Materials II

Raveling

The progressive disintegration of an HMA layer from the surface downward as a result of the dislodgement of aggregate particles.

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Raveling due to low density Raveling from snowplow operations

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Asphalt and Asphalt Mixtures

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Winter Quarter 2019 92

Construction Methods & Materials II

Raveling – Possible Causes Loss of bond between aggregate particles

and the asphalt binder as a result of:

A dust coating on the aggregate particles that forces the asphalt binder to bond with the dust rather than the aggregate.

Aggregate Segregation. If fine particles are missing from the aggregate matrix, then the asphalt binder is only able to bind the remaining coarse particles at their relatively few contact points.

Inadequate compaction during construction. High density is required to develop sufficient cohesion within the HMA.

Mechanical dislodging by certain types of traffic (studded tires, snowplow blades or tracked vehicles).

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Raveling due to inadequate

compaction caused by cold weather

paving