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Mix Design for HMA Mix Design for HMA RecyclingRecycling

National Symposium on HMA Energy & RecyclingOctober 9, 2007Recycling Group

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Do You Need A Mix Design?

Yes!!!!

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Do You Need To Account for Properties of RAP?

Asphalt BinderAggregateAsphalt Binder Content

Yes!!!!

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Are Mix Designers Concerned About the Following?

Yes Yes

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Are Mix Designers Concerned About the Following?

Yes Yes

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Guidance

NAPA – Quality Improvement Series 124Purdue - NCHRP Web Document 30Purdue - NCHRP Report 452New NCHRP Study

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Materials Evaluation

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Virgin Asphalt Considerations

0 to 15% no change in binder grade16 to 25% one temperature grade lower (high and low end)>25% use blending charts

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Blending Charts

46

52

58

64

70

76

82

0 10 20 30 40 50 60 70 80 90 100

Percentage of RAP

Failu

re T

empe

ratu

re fo

r Hig

h Te

mpe

ratu

re S

tiffn

ess

of A

spha

lt B

inde

r, °C

46

52

58

64

70

76

82

Failu

re T

empe

ratu

re fo

r Hig

h Te

mpe

ratu

re S

tiffn

ess

of A

spha

lt B

inde

r, °C

Failure temperature of 79.7°C for RAP

Failure temperature of 58.8°C or greater for virgin asphalt binder

Desire a high temperature grade of 64°C

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Importance of Blending Charts

1

10

100

70 76 82 88

Temperature, °C

Hig

h Te

mpe

ratu

re S

tiffn

ess

of E

xtra

cted

and

R

ecov

ered

Asp

halt

Bin

der,

G*/s

inδ,

kPa

Location 1 Location 2 Location 3 Location 4 Location 5

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What Happens During Mixing with RAP?

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Looking at the Asphalt Films

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Air voidsVirgin BinderRAP Binder

Aggregate

Time 0

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Air voids

Blended Binder

Extent of virgin binder diffusion

RAP Binder, no virgin binder diffusionTime 0 + X

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Air voids

RAP Binder,no virgin binder diffusion

Completely blended binder

Extent of virgin binderdiffusion

Time 0 + Y

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Importance of Material Variability

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8

Sample Number

Hig

h Te

mpe

ratu

re S

tiffn

ess

of E

xtra

cted

and

Rec

over

ed A

spha

lt B

inde

r, 88

°C G

*/sin

d, k

Pa

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Aggregate Considerations

ShapeSurface textureSpecific gravityFrictionOther properties

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QC from RAP (Asphalt Free Gradations)

Test #Reflux Asphalt

Content, %DWA 3/4-in 1/2-in 3/8-in No. 4 No. 16 No. 50 No. 2001 3.25 100 98 89 66 48 27 12.32 3.52 100 99 91 70 42 23 10.93 3.93 100 100 96 74 46 26 11.84 3.83 100 98 92 74 45 22 8.65 3.79 100 98 92 73 45 25 11.76 3.05 100 98 91 66 39 22 11.47 3.31 100 97 90 68 41 23 11.38 3.47 100 98 91 72 44 24 10.4

Average 3.52 100 98 92 70 44 24 11.1 Standard Deviation 0.31 0.0 0.9 2.1 3.4 2.9 1.9 1.1

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Mix Design Procedure

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Mix Considerations

VolumetricsGradationAsphalt binderEngineering properties

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Mix Considerations

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Plant Verification

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Plant VerificationDate

Sampled Sample LocationTest

Purpose

% Passing 3/4 in.

% Passing 1/2 in.

% Passing 3/8 in.

% Passing

No. 4

% Passing No. 16

% Passing No. 50

% Passing No. 200

Asphalt Content %, DWA

100 95 80 54 3.00100 100 90 64 7.00100 98 87 60 32 16 6.21

4/9/2007 Hot Sample Process 100.0 98.7 90.8 65.1 33.6 17.4 6.8 4.824/9/2007 Hot Sample Process 100.0 98.8 87.5 59.5 30.0 15.3 6.1 4.80

4/10/2007 Hot Sample Process 100.0 97.5 86.7 61.6 31.4 15.5 5.8 5.044/10/2007 Hot Sample Process 100.0 97.9 89.7 65.5 31.5 15.2 5.6 5.074/11/2007 Hot Sample Process 100.0 97.9 89.7 65.5 31.5 15.2 5.6 5.074/11/2007 Hot Sample Process 100.0 98.4 89.3 63.8 32.9 15.8 6.5 5.094/12/2007 Hot Sample Process 100.0 97.4 82.9 55.3 28.6 15.0 5.5 5.144/13/2007 Hot Sample Process 100.0 100.0 92.0 66.7 33.3 16.5 6.1 4.804/16/2007 Hot Sample Process 100.0 100.0 93.0 69.0 34.8 16.3 6.4 5.314/16/2007 Hot Sample Process 100.0 100.0 96.1 67.5 34.0 17.0 6.44/16/2007 Hot Sample Process 100.0 100.0 88.6 62.0 34.9 18.3 7.14/16/2007 Hot Sample Process 100.0 98.6 90.5 64.9 38.6 21.5 9.44/16/2007 Hot Sample Process 100.0 97.1 85.3 57.4 30.0 15.4 5.4 5.014/17/2007 Hot Sample Process 100.0 100.0 91.4 60.0 31.1 16.1 5.2 4.964/17/2007 Hot Sample Process 100.0 97.2 86.1 59.7 31.8 17.1 6.8 5.194/17/2007 Hot Sample Process 100.0 97.3 86.3 64.4 36.4 18.7 7.1 5.074/17/2007 Hot Sample Process 100.0 96.7 86.7 60.0 31.1 16.3 6.3 4.774/17/2007 Hot Sample Process 100.0 97.3 87.8 58.1 31.2 15.9 6.1

18 18 18 18 18 18 18 14100.0 98.4 88.9 62.6 32.6 16.6 6.35 5.010.0 1.2 3.1 3.8 2.5 1.6 0.94 0.16

MeanStandard Deviation

Min RequirementMax RequirementMix Design Targets

Number

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Some States Do Not Allow RAP. Why?

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Conclusions

Do we need a mix design?Do we need to consider the properties of RAP?Guidelines

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Questions