flexible pavement materials characterization for the 2002 ...flexible pavement materials...

Flexible Pavement Materials Characterization for the 2002 Pavement Design Guide

Ramon Bonaquist, Ph.D., P.E.Chief Operating Officer

Advanced Asphalt Technologies, LLC

New Jersey PavementTechnology Workshop

February 25, 2003


“Engineering Services for the Asphalt Industry”

Acknowledgements

• NCHRP Project 1-37A– Dr. Amir Hanna– Project Panel

• ERES Consultants– Prime Contractor

• Professor Matthew W. Witczak– Flexible Pavement Team Leader

• Members of the Flexible Pavement Team



Outline

• Overview of 2002 Flexible Pavement Design Process

• Importance of Material Characterization• Hierarchical Approach for Design Inputs• Flexible Pavement Materials

Characterization– Asphalt Concrete– Subgrade and Unbound Base/Subbases

• Summarize



Design ProcessFoundation

AnalysisClimate Material

PropertiesTraffic Analysis

ModifyStrategy

InputsAnalysis

No

Trial Design Strategy

Pavement Response Model

MeetPerformance

Criteria?Distress Prediction Models

ConstructabilityIssues

Viable Alternatives Life Cycle CostAnalysis

Select Strategy

Yes

DamageAccumulation

Strategy Selection



Distresses

FatigueCracking

Thermal Cracking

Longitudinal Cracking

IRI

Rutting



Damage

TIME

Criteria

TIME

FATIGUECRACKING

RUTDEPTH Criteria

DesignPeriod



Materials in Design ProcessFoundation

AnalysisClimate Material

PropertiesTraffic Analysis

ModifyStrategy

InputsAnalysis

No

Trial Design Strategy


MeetPerformance

Criteria?Distress Prediction Models

ConstructabilityIssues

Viable Alternatives Life Cycle CostAnalysis

Select Strategy

Yes

DamageAccumulation

Strategy Selection




• Multilayer Elastic Solution– JULEA

• Material Properties– Modulus– Poisson’s Ratio

εt

ε

δ

C



tε

tε

3f32f21

kk

t1ff E

11kNββ

εβ

=

From LayeredElastic Analysis

Field Calibration Factors

Fatigue Cracking

Modified Shell Fatigue Equation

Asphalt Modulus



Hierarchical Design Inputs

PoorDefaults, Judgement3

FairRegression equations, Regional values

2

GoodProject/Segment Specific Measurements

1

Knowledge of Input Parameter

Determination of Input Values

Input Level



New Asphalt Concrete

• Modulus Mastercurve– Structural Response– Rutting and Fatigue

• Low Temperature Creep Compliance and Strength– Thermal Cracking Analysis

• Poisson’s Ratio Predicted From Modulus



Mastercurve

100

1,000

10,000

100,000

-6 -4 -2 0 2 4 6

Log Frequency (Hz)

E*

MPa

-9°C4.4 °C21.1 °C37.86C54.4°C

Reference Temperature 21.1 °C

100

1,000

10,000

100,000

-6 -4 -2 0 2 4 6

Log Reduced Frequency (Hz)

E*

MPa

-9°C4.4 °C21.1 °C37.86C54.4°CMaster Curve

-6-4-20246

-20 0 20 40 60Temperature, °C

log

a(T)

)(log)log()log( Taffr −=



Compliance

1.E-07

1.E-06

1.E-05

1.E-04

1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10

Loading Time, s

D(t

), 1/

psi

3214-4D(t)^



New Asphalt Concrete

Input Level Property Characterization Method

Modulus Dynamic Modulus |E*| Test ASTM D3496Creep/Strength Indirect Tensile Creep/Strength AASHTO TP9Modulus Predicted From Volumetrics and Binder PropertiesCreep/Strength Extrapolated From limited Creep/Strength TestsModulus Predicted From Volumetrics and Binder GradeCreep/Strength Predicted From Binder Grade

1

2

3



Dynamic Modulus TestLevel 1

σc

∆σ

StressStrain

Time

Phase Lag

*E σε

=(ASTM D3496, NCHRP 9-19)



Witczak Predictive EquationLevels 2 and 3



Witczak Predictive Equation

0.1

1

10

100

0.1 1 10 100

Measured E (10^5 psi)

Pred

icte

d E

(10^

5 ps

i)

new database

original database



Creep and StrengthLevel 1

AASHTO TP9

1.E-07

1.E-06

1.E-05

1.E-04

1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10

Loading Time, s

D(t)

, 1/p

si

3214-4D(t)^



Creep and StrengthLevels 2 and 3

m

TTC r

tDDtD

+= − )(10 210

)(

Function of Material Characteristics

D(t) = Compliancet = timeT = TemperatureTr = Reference Temperature



Existing Asphalt Concrete

• Damaged Modulus– Structural Response– Rutting and Fatigue

• Poisson’s Ratio Predicted From Modulus



Damaged Modulus Mastercurve

Damaged Modulus Mastercurves

100

1000

10000

100000

1000000

10000000

1E-08 0.000001 0.0001 0.01 1 100 10000 1000000 1E+08

Reduced Time

Mod

ulus

(psi

)

0.000.200.501.001.502.003.005.0010.0020.00

Fatigue Damage



Existing Asphalt Concrete

Input Level Modulus Characterization Method

Damaged Backcalculated from NDTUndamaged Predicted From Volumetrics & Binder Properties From CoresDamaged From Extent of Fatigue CrackingUndamaged Predicted From Volumetrics & Binder Properties From CoresModulus From Condition RatingUndamaged Predicted From Volumetrics and Binder Grade

1

2

3



Existing Asphalt ConcreteLevel 1


100

1000

10000

100000

1000000

10000000

1E-08 0.000001 0.0001 0.01 1 100 10000 1000000 1E+08

Reduced Time

Mod

ulus

(psi

)

0.000.200.501.001.502.003.005.0010.0020.00

Fatigue DamageUNDAMAGED MODULUS

NDT REDUCED TIME

NDT MODULUSDAMAGE



Existing Asphalt ConcreteLevel 2 and 3


100

1000

10000

100000

1000000

10000000

1E-08 0.000001 0.0001 0.01 1 100 10000 1000000 1E+08

Reduced Time

Mod

ulus

(psi

)

0.000.200.501.001.502.003.005.0010.0020.00

Fatigue DamageUNDAMAGED MODULUS

FROM CRACKINGOR

CONDITION RATING

DAMAGED MODULUS



Unbound Materials

RM σε

∆=∆

εc

σc

∆ε

∆σ MR

εa

σa

• Resilient Modulus – Structural Response– Rutting

• Poisson’s Ratio Estimated From Modulus



Stress Dependence of MR

2 3k k

octR 1 a

a a

M k p 1p p

τθ= +

(NCHRP 1-28A)

Bulk (Confining) Stress• Stiffening term (k2 > 0)• Dominates for coarse

granular soils (base, subbase)

Shear (Deviatoric) Stress• Softening Term (k3 < 0)• Dominates for fine-grained

soils (subgrade)



Moisture Effects on MR

( )1 exp ln

10m opt

R env Ropt

b aab k S Sa

env

M F M

F

− +

+ − + −

=

=S = degree of saturationS = saturation at OMCk = regression coefficientma,b = constants (function of soil type)

S = degree of saturationS = saturation at OMCkm= regression coefficienta,b = constants (function of soil type)



Moisture Effects on MR

Coarse Grained

Fine Grained



Unbound Materials

Input Level

Design Type Characterization Method

New Laboratory Resilient Modulus (MR) testRehab NDT backcalculated MR

New MR = f (other properties)Rehab MR = f (other properties)New MR = f (soil classification)Rehab MR = f (soil classification)

1

2

3



Unbound MR: Level 1 New

RM σε

∆=∆

εc

σc

∆ε

∆σ MR

εa

σa

LTPP P-46/AASHTO T307



Unbound MR: Level 1 Rehab

• Backcalculate From FWD

• EDESIGN=CF(EFWD)– CF= user defined

Typical values: CF = 0.40 for subgrade, 0.67 for base/subbase



• Correlations to Other Tests– DCP CBR=(292/PR)1.12

– CBR MR=2555(CBR)0.64 psi

– R-value MR = 1155+555(R) psi

• Correlations Using Gradation and PI• Conversion of Layer Coefficient

– MR=30000(ai/0.14)3 psi

Unbound MR: Level 2



50 6040302015108654321.5

1 2 3 4 5 10 15 20 40 60 80 100

1008060403020151054321

P oor M edium G ood Exce llen tS u b g rad e S o il C ateg ory

A A S H TO S o ilC lassification

M r (ks i)

C B R (% )

R - Valu eA -1-b

A -2-7A -3

A-4A -5

A -6

A -7-6

A-1-a

A -7-5

A -2-5A -2-4

A -2-6

Unbound MR: Level 3



Other Materials

• Portland Cement Concrete• Cementitiously Stabilized Materials

– CTB– Soil Cement

• PCC Slabs– Intact– Rubbilized

Resonant Pavement Breaker



Summary

• Modulus is Key Material Input Parameter

• Hierarchical Input Levels– Level 1: Measured– Level 2: Correlations– Level 3: Defaults

• Agency Choice

50 6040302015108654321.5

1 2 3 4 5 10 15 20 40 60 80 100

1008060403020151054321

P oor M edium G ood Exce llen tSu b g rade So il C ateg o ry

A A S H T O S oilC lassification

M r (ks i)

C B R (% )

R - Valu eA -1-b

A-2-7A-3

A -4A-5

A -6

A -7-6

A -1 -a

A -7-5

A-2-5A -2-4

A -2-6



Summary

• New and Rehabilitation• Load Influences Addressed

– Rate for AC– Stress State for Unbound

• Environmental Influences Addressed– Temperature in AC– Moisture in Unbound

Resonant Pavement Breaker



Questions?

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