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10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create...

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Marshall Mix Design
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Page 1: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

Marshall Mix Design

Page 2: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 2

Asphalt Concrete Properties

Stability

Workability

Skid Resistance

Durability

Stripping

Fatigue Cracking

Thermal Cracking

Bleeding

Page 3: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 3

Stability

The ability to withstand traffic loads withoutdistortion or deflection, especially at highertemperatures.

To get good stability, use strong, rough, dense-graded, cubical aggregatewith just enough binder to coat the aggregate particles. Excess asphaltcement lubricates the aggregate particles and lets them slide past eachother more easily (which reduces stability). But a thick asphalt coatingprovides good flexibility to resist cracking, which is desirable. Hmmm…

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CIVL 3137 4

Workability

The ability to be placed and compacted withreasonable effort and without segregation ofthe coarse aggregate.

Too much asphalt cement makes the mix tender. Too little asphalt cementmakes it hard to compact. Too much natural sand can also make the mixtender because natural sand has smooth, round grains. Hmmm…

Page 5: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 5

Skid Resistance

Proper traction in wet and dry conditions.

To get good skid resistance, use smaller aggregate so there are lots ofcontact points, use hard aggregate that doesn’t polish and make sure youhave enough air voids to prevent bleeding.

Some states now use an open-graded friction course (OGFC) that allowswater to drain to the sides of the pavement, eliminating hydroplaning. ButOGFC is not very durable because of the open pores. Hmmm…

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CIVL 3137 6

Durability

The ability to resist aggregate breakdown dueto wetting and drying, freezing and thawing,or excessive inter-particle forces.

To get good durability, use strong, tough, nonporous aggregate andenough asphalt cement to completely coat all of the aggregate particles(to keep them dry) and fill all of the voids between particles (to slow theoxidation of the asphalt cement). But this reduces stability. Hmmm…

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CIVL 3137 7

Stripping

Separation of the asphalt cement coating fromthe aggregate due to water getting betweenthe asphalt and the aggregate.

To reduce stripping, use clean, rough, hydrophobic aggregate and addenough asphalt cement to provide a thick coating of asphalt on everyaggregate particle. This improves durability but decreases stability.

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CIVL 3137 8

Bleeding

The migration of asphalt cement to the surfaceof the pavement under wheel loads, especiallyat higher temperatures.

To prevent bleeding, incorporate enough air voids so the asphalt cancompress by closing air voids rather than by squeezing asphalt cementout from between the aggregate particles.

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CIVL 3137 9

Fatigue Cracking

Cracking resulting from repeated flexure ofthe asphalt concrete due to traffic loads.

To minimize fatigue cracking, use the proper asphalt cement grade andhave a thick asphalt cement coating to make the concrete flexible. Thisimproves durability but decreases stability.

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CIVL 3137 10

Thermal Cracking

Cracking that results from an inability toacclimate to a sudden drop in temperature.

To minimize thermal cracking, use the proper asphalt cement grade.

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CIVL 3137 11

Mix Design Basics

The right grade of asphalt cementRelates to fatigue cracking, thermal cracking, stability

The right type of aggregateRelates to stability, durability, stripping, skid resistance

The right mix volumetricsRelates to stability, durability, stripping, bleeding, skid resistance

Page 12: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 13

Marshall Mix Design

Bruce Marshall, Mississippi Highway Department

Page 13: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

Marshall Mix Design Steps

1. Create aggregate blend to meet gradation specifications.

2. Establish mixing and compaction temperatures from the viscosity-temperature chart.

3. Compact three specimens at each of five asphalt contents spanning the expected optimum asphalt content.

4. Determine the relative density of each specimen and the mix volumetrics (mb, AV, VMA, VFA).

5. Measure the performance properties of the each specimen at 60ºC (140ºF).

CIVL 3137 14

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CIVL 3137 15

Marshall Specimens

Traffic Blows / Side

Light 35

Medium 50

Heavy 75

10#18"

Make 3 specimens at each of5 different asphalt contents

Page 15: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 16

Marshall Hammer

Mold

Hammer

Page 16: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 24

Stability and Flow Test

140oF

flow

stability

deflection(0.01 in)

load(lbs)

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CIVL 3137 25

Stability and Flow Test

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CIVL 3137 26

Marshall Mix Design

159

160

161

162

163

164

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Uni

t Wei

ght (

pcf)

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CIVL 3137 27

1500

1600

1700

1800

1900

2000

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Mar

shal

l Sta

bilit

y (lb

s)

Marshall Mix Design

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CIVL 3137 28

1

2

3

4

5

6

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Air

Voi

ds (%

)

Marshall Mix Design

Page 21: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 29

0

5

10

15

20

25

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Flow

Marshall Mix Design

Page 22: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 30

50

60

70

80

90

100

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Void

s Fill

ed w

ith A

spha

lt (%

)

Marshall Mix Design

Page 23: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 31

Marshall Mix Design

%7.43

3.47.41.5AC

MaximumDensity

MaximumStability

4% AirVoids

(The Asphalt Institute Procedure)

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CIVL 3137 32

Marshall Mix Design

5.1

AC 4.7

4.3

4.3%1

MaximumDensity

MaximumStability

4% AirVoids

(The NAPA Procedure)

ThisiswhatTDOTuses

Page 25: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 34

Page 26: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 35

VMA CriteriaM

inim

um V

MA

(%)

10

Nominal Maximum Particle Size

20

30

40

50

2"1½"1"¾"½"4 3/8"840

Deficient in either

asphalt or air voids

(Assuming 4% Design Air Voids)

Page 27: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 36

VMA CriteriaM

inim

um V

MA

(%)

10

Nominal Maximum Particle Size

20

30

40

50

2"1½"1"¾"½"4 3/8"840

Deficient in either

asphalt or air voids

(Assuming 5% Design Air Voids)

1%

Page 28: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 37

VMA CriteriaM

inim

um V

MA

(%)

10

Nominal Maximum Particle Size

20

30

40

50

2"1½"1"¾"½"4 3/8"840

Deficient in either

asphalt or air voids

(Assuming 3% Design Air Voids)

1%

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CIVL 3137 38

1500

1600

1700

1800

1900

2000

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Mar

shal

l Sta

bilit

y (lb

s)

Marshall Mix Design

Page 30: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 39

0

5

10

15

20

25

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Flow

Marshall Mix Design

Page 31: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 40

1

2

3

4

5

6

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Air

Voi

ds (%

)

Marshall Mix Design

Page 32: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 41

50

60

70

80

90

100

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

Void

s Fill

ed w

ith A

spha

lt (%

)

Marshall Mix Design

Page 33: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 42

VMA CriteriaM

inim

um V

MA

(%)

10

Nominal Maximum Particle Size

20

30

40

50

2"1½"1"¾"½"4 3/8"840

Deficient in either

asphalt or air voids

Page 34: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 43

13

14

15

16

17

18

3.5 4.0 4.5 5.0 5.5 6.0 6.5

Asphalt Content (%)

VM

A (%

)

Marshall Mix Design

TDOT requiresthe AC to be lessthan that whichminimizes VMA

Page 35: 10 - Marshall Mix Design - Memphis Handouts/10 - Marshall...Marshall Mix Design Steps 1. Create aggregate blend to meet gradation specifications. 2. Establish mixing and compaction

CIVL 3137 44

Ways to Increase VMA

1. Reduce the dust content2. Open the aggregate gradation3. Gap-grade the aggregate blend4. Increase manufactured sand5. Reduce flat-and-elongated particles

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CIVL 3137 45


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