Kamil E. Kaloush PhD, P.E.Associate Professor

September 15th 2009

Mechanistic-Empirical Pavement Design Guide Implementation and Pavement

Preservation Strategies with A-R

“Cut Cost with Asphalt-Rubber” Seminar Columbus, OH

AgendaMEPDGConventional Versus Asphalt Rubber Mixturesmaterial properties input and implementation requirements into the MEPDG issues for short term implementation recommendations for future / long term implementation

ARFC benefits as a pavement preservation strategy

Mechanistic-Empirical Pavement Design Guide-MEPDG

Based on Mechanistic-Empirical principals.Relates pavement material characteristics with their

performance in the field.Calibrated based on data from the LTPP Project.Capability to adapt to local conditions Special emphasis in the design of rehabilitated

pavements

Hierarchical Design Inputs in the MEPDG

Level 1: Accurate data from laboratory testingLevel 2: Intermediate level of accuracy. Inputs

estimated through correlations Level 3: Lowest level of accuracy. Default

values provided by the program

Input for the Asphalt Concrete Layera. Asphalt General – mix volumetricsb. Asphalt Binder – consistency tests /

AC/PG gradeASTM Ai-VTSi

c. Mix Stiffness – Dynamic Modulus

8628.4)sin

1(10

*

G

))log(393532.0)log(313351.0603313.0(34

238384

42

200200

1005470.0)(000017.0003958.00021.0871977.3

802208.0058097.0

002841.0)(001767.002932.0750063.3*log

f

aeff

effa

e

VVV

V

E

MEPDG Outputa. Permanent Deformationb. Cracking: Transverse, Longitudinal, Fatiguec. Thermal Crackingd. Roughness, IRI

Asphalt Rubber Mixtures

ADOT uses AR mixes for new and rehabilitated pavements.

In 1999, ADOT and ASU joint research program: several AR mixes and binders have been characterized, and some are currently being tested at ASU.

Goal of implementing AR in the MEPDG

To date, over 20 projects included AR mixtures that were tested.

 

1

35

4

2

6

7

8

9

10

11

ASTM D8Standard Definitions of Terms Relating to Materials for Standard Definitions of Terms Relating to Materials for

Roads and PavementsRoads and Pavements

Asphalt Rubber– a blend of asphalt cement, reclaimed tire rubber and certain additives in which the rubber component is at least 15% by weight of the total blend and has reacted in the hot asphalt cement sufficiently to cause swelling of the rubber particles.

Interacted Rubber 1-2 mm Particles

Existing or new HMA Base Mix

AR Bitumen 6.8- 8%Air Voids 7 - 10%

AR Bitumen Content 8.8 - 10%Air Voids 18 - 20%

Typical HMA Cross Section

ARFC13 mm

ARAC

50 mm ARAC

OpenGap / 

SMA

Dense

Base Asphalts for AR Use

Type 1: Hot Climate PG 64-16 Type 2: Moderate Climate PG 58-22 Type 3: Cold Climate PG 52-28

Asphalt Rubber Modified Binder

0

0.2

0.4

0.6

0.8

1

1.2

2.7 2.75 2.8 2.85 2.9 2.95

Log-Temperature (Rankine)

Log

log-

Visc

osity

(cP)

I-17 Project AR 58-22I-17 Project AR PG 64-16I-17 Project PG 58-22I-17 Project PG 64-16ADOT Virgin PG 76-16

Two Original and modified AR binders (at RTFO):PG 58-22PG 58-22ARPG 64-16 PG 64-16 AR

A and VTS

Permanent Deformation - Initial Findings

ARFC (in) ARAC (in) Conventional (in)

Sub total AC (in)

Sub total Base-

Subgrade (in)

Total Rutting (in)

1 0.09 0.25 0.03 0.37 0.27 0.642 0.11 0.33 0.04 0.48 0.3 0.783 0.15 0.44 0.05 0.64 0.32 0.954 0.18 0.51 0.06 0.75 0.33 1.085 0.21 0.59 0.07 0.86 0.34 1.216 0.23 0.67 0.08 0.97 0.35 1.327 0.25 0.72 0.08 1.05 0.35 1.48 0.27 0.77 0.09 1.12 0.36 1.489 0.28 0.81 0.09 1.18 0.36 1.55

10 0.29 0.85 0.1 1.24 0.37 1.6

Buffalo Range Project - Unconfined E* -Default MEPDG Rutting Coefficients

Year

Rutting (in)

0.00

0.50

1.00

1.50

2.00

0 2 4 6 8 10 12Pavement Age (years)

Rut

ting

(in)

Total AC Rutting Total Rutting

Field

Field Stresses - Lab Confinement Issues

Mixtures CharacteristicsTemp (oF)

Freq (Hz)

Dynamic Modulus (ksi) Conventional ARAC ARFC

Unconfined Confined Unconfined Confined Unconfined Confined 14 25 5464 5131 3850 4710 2166 2763

10 5079 4782 3654 4566 2079 2612 5 4803 4504 3466 4374 1956 2456 1 4260 3954 3059 3779 1668 2103

0.5 4046 3708 2890 3520 1548 1950 0.1 3508 3101 2468 2963 1294 1621

40 25 3287 3518 2684 3842 1353 1779 10 3016 3136 2522 3553 1246 1612 5 2815 2895 2354 3266 1133 1463 1 2336 2344 1971 2635 908 1149

0.5 2142 2120 1810 2365 817 1030 0.1 1722 1687 1460 1821 625 781

70 25 2190 2152 1563 2182 751 1030 10 1902 1892 1362 1932 645 915 5 1679 1682 1205 1688 557 799 1 1260 1277 890 1212 386 559

0.5 1091 1128 770 1038 325 480 0.1 769 837 532 714 223 338

100 25 730 715 511 881 297 602 10 578 615 397 715 238 544 5 493 558 324 598 196 484 1 335 404 210 379 132 351

0.5 284 356 173 312 112 310 0.1 200 272 114 217 81 250

130 25 321 339 215 574 197 534 10 254 297 163 470 153 451 5 219 266 133 370 127 385 1 157 204 90 242 87 292

0.5 138 199 78 210 76 260 0.1 104 167 59 168 59 223

130 25 321 339 215 574 197 534 10 254 297 163 470 153 451 5 219 266 133 370 127 385 1 157 204 90 242 87 292

0.5 138 199 78 210 76 260 0.1 104 167 59 168 59 223

Temp (oF)

Freq (Hz)

Dynamic Modulus (ksi) Conventional ARAC ARFC

Unconfined Confined Unconfined Confined Unconfined Confined

E* Master Curves

10,000

100,000

1,000,000

10,000,000

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

Log Reduced Time (sec)

E*

(psi

)

I40 BR ARAC-10 psi I40 BR ARAC-20 psi I40 BR ARAC-30-psi I40 BR ARAC 0psi

10,000

100,000

1,000,000

10,000,000

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

Log Reduced Time (sec)

E*

(psi)

ARFC-Unconfined Confined 10 psi Confined-20 psi Confined-30 psi

ARAC

ARFC

Level 3 Issues – E* Predictive Equation

WE* not calibrated for AR mixes.

))log(393532.0)log(313351.0603313.0(34

238384

42

200200

1005470.0)(000017.0003958.00021.0871977.3

802208.0058097.0

002841.0)(001767.002932.0750063.3*log

f

aeff

effa

e

VVV

V

E

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07

Measured E* (psi)

Pred

icte

d E*

(psi

)

Data Point=1494, se/sy=0.97 (arithm), 0.96(log)R2=0.076 (arithm) 0.08(log)

Calibrated WE* Equation for AR Mixes-Unconfined

CURRENT EQUATION

NEW PARAMETERS

COEFFICIENT

INTERCEPT 1 3.750063 0.346064

P200 0.029320 0.720506

P2002 -0.001767 -0.2661

P4 -0.002841 0.068005

VA -0.058097 -0.042026

VBEFF -0.802208 -0.067019

INTERCEPT 2 3.871977 4.87167

P4 -0.002100 0.04564

P38 0.003958 0.036857

P382 0.000017 -0.001059

P34 0.005470 0.00547

KF -0.603313 -0.175293

KV 0.313351 -0.480331

BF -0.3953 -0.741099

LOG SE /SY 0.96 0.23

R2 0.08 0.95

ARITHMETICSE /SY 0.97 0.32

R2 0.08 0.90

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+04 1.0E+05 1.0E+06 1.0E+07

Measured E* (psi)

Pred

icte

d E*

(psi

)

Data Point=1494, se/sy=0.32 (arithm), 0.23(log)R2=0.90 (arithm), 0.95(log)

Dynamic Modulus E*

Calibrated WE* Equation for AR Mixes-ConfinedNew parameters

4.09180.7084-0.18020.0169-0.0284-0.5883-0.67510.03150.0494-0.00130.00550.2338-0.6026-0.6419

Se/Sy 0.32R2 0.9

Se/Sy 0.4R2 0.84Arithmetic

Kf

Kv

bf

Log

p4

p38

p382

p34

p4

Va

Vbeff

Intercept 2

CoefficientIntercept 1

p200

p2002

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Pred

icte

d E*

(psi

)

Measured E* (psi)

Data Point=1260, se/sy=0.399 (arithm), 0.32(log)R2=0.84 (arithm) 0.90(log)

What about the binders?

No PG Grading For AR Mixes included in the MEPDG

Alternative:find the PG grading that best match the Ai and VTSi values for asphalt rubber binders.

Binder Type Ai VTSi

PG 58-22 AR 8.543 -2.781PG 64-40 8.524 -2.798

PG 64 -16 AR 8.048 -2.598PG 70-40 8.129 -2.648

Other MEPDG Issues

• Limitation of the current version of the MEPDG:– Minimum thickness

ARFC 0.5"ARAC 2"

Conventional

Aggregate Base

Subgrade

Other MEPDG Issues– Multiple layers of

mixtures that were not included in calibration;

– Need to re-calibrate

ARFC 0.5"ARAC 2"

Conventional

Aggregate Base

Subgrade

39937.0734.115552.310 NTr

p

Alternative MEPDG RunsDefault or Specific Layer MEPDG rutting

coefficients and E* unconfined / Confined results.

332211

rr aar

r

p NTa

r1 = 0.509r2 = 0.90r3 = 1.2

ARFC 0.5"ARAC 2"

Conventional

Aggregate Base

Subgrade

r1 r2 r3

r1 r2 r3

Permanent Deformation – Case Study

Constructed in 2001(I-40, MP=225)

Asphalt binder and asphalt mix data from laboratory test results (Level 1)

MR =25,000 psi

AADTT =15,000

Design life period =10 years.

Description of the project ARFC 1", AC=8.8%, Va=18%

ARAC 1.5", AC=6.8%, Va=11%

Conventional 4", AC=4.8%, Va=7%

Aggregate Base 8"

Subgrade

Selected Material 12"

Permanent Deformation Results

ARFC (in) ARAC (in) Conventional (in)

Sub total AC (in)

Sub total Base-

Subgrade (in)

Total Rutting (in)

1 0 0.04 0.04 0.09 0.24 0.332 0 0.06 0.06 0.12 0.26 0.383 0 0.08 0.08 0.15 0.28 0.434 0 0.09 0.09 0.18 0.29 0.475 0 0.1 0.1 0.21 0.3 0.516 0 0.12 0.12 0.23 0.31 0.547 0 0.12 0.13 0.25 0.31 0.568 0 0.13 0.13 0.27 0.31 0.589 0 0.14 0.14 0.28 0.32 0.6

10 0 0.15 0.15 0.3 0.32 0.62

Buffalo Range Project -Confined E*- Default MEPDG Rutting Coefficients

Year

Rutting (in) Default MEPDG rutting coefficients and the E* confined results:- AC rutting drastically reduced to 0.3”. - All runs over predicts rutting, but this approach gives the best prediction.

0.00

0.20

0.40

0.60

0.80

0 2 4 6 8 10 12Pavement Age (years)

Rutti

ng (i

n)

Total AC Rutting Total Rutting

Field

0.00

0.50

1.00

1.50

2.00

0 2 4 6 8 10 12Pavement Age (years)

Rut

ting

(in)

Total AC Rutting Total Rutting

Field

Fatigue Cracking Model

32

32

)()(1111

kkt

kk

tf Ek

EkN

Min Max k1 1.20E-08 7.50E-01 k2 4.2 8.2 k3 1.3 2.6 k1 3.00E-05 8.00E+03 k2 3 6.7 k3 1.5 2.7 k1

k2

k3

Regression Coefficients k1, k2, k3

ARAC

ARFC

MEPDG7.60E-03

3.951.28

Evaluation of Fatigue Cracking

7 years field distress survey: fatigue cracking approximately 7%. Use of confined E* and specific ARAC coefficients seems to help in better predicting of fatigue cracking.

1 0.48 0.44 0.47 0.442 3.53 3.04 3.31 3.033 12.4 9.75 11.21 9.734 20.29 13.2 17.07 13.145 26.31 13.94 20.71 13.826 31.97 14.05 24.00 13.887 37.60 14.17 27.42 13.958 42.92 14.30 30.83 14.019 47.74 14.43 34.14 14.0810 52.03 14.55 37.30 14.14

Total Cracking at Surface (%)

YearUnconfined-

Default Coefficients

Unconfined-ARAC

Coefficients

Confined-Default

Coefficients

Confined-ARAC

Coefficients

AR binders had improved viscosity-temperature susceptibility. Crumb rubber bumps up the PG by at least one level.

AR Binder: find PG that best match the Ai and VTSi values.

Unconfined / Confined E* tests: effect of confinement on moduli values more pronounced for AR mixtures.

Level 1: Must use confined E* test results / Master Curves.

Level 3: use modified WE* equation; if nothing else, use it to genereae dynamic modulus input data for Level 1 analysis.

Minimum AC layer thickness: use 1 in thick layer for ARFC and subtract difference from others; or completely ignore ARFC layer.

Concluding Remarks – Input MEPDG Data

Concluding Remarks – MEPDG Output

For Permanent Deformation / Rutting model: use existing model and confined E* >> best predictions.

Consider a recalibration on the AC Rutting Model based on all mixtures (Conventional, ARAC, and ARFC) until future MEPDG versions allows entering different set of calibration coefficients.

Confined E* and specific ARAC coefficients provide better prediction of fatigue cracking.

For future fatigue cracking analysis, run the MEPDG with the calibrated fatigue coefficients that are specific to the AC layer where fatigue cracking will initiate.

Is ARFC a Good Pavement Preservation Strategy?

1. Performance2. Friction / Safety3. Ride Quality / Comfort 4. Thermal Gradient / Urban Climate Interaction5. Highway Noise6. Tire Wear Emissions / Air Quality7. Life Cycle Cost8. Energy Consideration

Asphalt Rubber Friction Course – 20 to 25 mm

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Years

AR

HMA

Percent Cracking

HMA

AR

I-10 TEST SECTIONS

AR-ACFC ¾”

SMA ¾”P-ACFC ¾”

PEM 1 ¼” ACFC ¾”Field Noise

Validation Studies

Tire / Pavement Noise (dB) for Arizona I-10 Test Sections

102.84

99.94

104.68

101.56102.17

99.8

101.0100.6

99.8

98.9

96

97

98

99

100

101

102

103

104

105

106

AR-ACFC ACFC P-ACFC PEM SMA

Tir

e / P

avem

ent N

oise

(dB

)

Dynatest 2008 at 100 Km/h Scofield-Donovan 2002 at 100 Km/h

Friction / SafetyAverage Friction Value LANE PCCP AR-ACFC I010EHOV 0.54 0.66 I010ELN1 0.60 0.61 I010ELN2 0.49 0.61 I010ELN3 0.47 0.60 I010ELN4 0.47 0.54

I010WHOV 0.51 0.58 I010WLN1 0.64 0.57 I010WLN2 0.50 0.59 I010WLN3 0.44 0.59 I010WLN4 0.42 0.58

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

50 250 450 650 850 1050 1250 1450 1650 1850 2050 2250 2450 2650

Fric

tion

Valu

e (M

u)

Friction average every 50 feet

Friction Test-Deck Park Tunnel I010 East HOV Lane @ 60 mph Comparison PCCP to AR-ACFC

PCCP

AR-ACFC

Profilometer Test-Deck Park Tunnel I010 East HOV Comparison PCCP to AR

102030405060708090

100110120130140150160170

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

2600

2700

Distance every 100ft

IRI(I

N/M

I)

PCCPA R

Ride Quality / RoughnessIRI (in/mi) LANE PCCP AR-ACFC

I010EHOV 96.34 43.57 I010ELN1 123.20 59.03 I010ELN2 104.29 48.81 I010ELN3 111.87 47.80 I010ELN4 115.30 52.91

I010WHOV 85.44 32.51 I010WLN1 87.94 37.79 I010WLN2 85.40 46.92 I010WLN3 96.83 46.11 I010WLN4 97.75 36.81

Field Investigation of PCC Thermal BehaviorTemperature

Gradients induce damaging Curling Stresses

Courtesy AZ511.com

Thermal Gradient Test Site

Thermal Gradients EffectThermal Blanket Effect

of ARFC reduces PCC Curling Stresses (8- 25%)

Observed benefits of porosity and lower thermal mass of the ARFC layer.

Urban Heat Island

Air Quality

Rare opportunity to sample tire wear emissions at the tunnel before and after the AR-ACFC overlay.

Deck Park Tunnel, I-10 Phoenix, AZ

Based on Tire Wear Tracers

Tire Wear Emission Rates

Emission rates calculated per kilometer driven (g/km).

Tire wear emission rate based on

Experiment 1 (PCC road surface)

Experiment 2 (AR-ACFC road surface)

Compound # 3 354 ± 71 177 ± 35 Compound # 4 172 ± 34 120 ± 24

May 2004 and June 2005

Cost BenefitsLonger Service LifeReduced cracking and maintenance.Reduced thickness.

0100200300400500600700800900

100011001200

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Year

Mai

nten

ance

Cos

t $/la

ne-K

m

Overlays / Inlays

AR-ACFC

Process kJ/kgTire Shedding -1744

Shred Transportation -1744

Granulation -3586CRM

Transportation -1744Steel Recovery 1900Asphalt Saved 209,325 to 465,168

Aggregate Saved 107,860Gain / Loss 310,267 to 566,109

½ Thickness Design Criteria

Energy Consideration

0

5,000

10,000

15,000

20,000

25,000

Production kg An. CO2 Eq. / km Mixing kg An. CO2 Eq. / km Transportation kg An. CO2 Eq. / km

Transportation kg An. CO2 Eq. / km 2,670 2,823 3,722

Mixing kg An. CO2 Eq. / km 6,834 4,124 11,210

Production kg An. CO2 Eq. / km 3,319 8,060 4,517

AR 2.5" over Base 6" UTW 2" over Base 6" HMA 4" over Base 6"

Positive Impact on CO2 Emissions

Conclusions• ARFC is a Pavement Preservation Strategy because:

– Performance / Durability √

– Safety √

– Ride Quality √

– Quality of Life Issues √• Highway Noise• Air Quality• Urban Heat Island

– Cost Effective

– Positive Impact on Energy / CO2 emmisions√

Arizona

Thank You! - kaloush@asu.edu