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UAA Professional Development Seminar

Sustainable Materials and Design for Alaskan Pavements

Jenny Liu, Ph.D., P.E.

University of Alaska Fairbanks

November 18, 2016

Background

Sustainable materials Warm mix asphalt (WMA)

Recycled asphalt pavement (RAP)

Paving interlayers

Materials characterization for pavement design Asphalt concrete (AC)

Asphalt treated base (ATB)

Granular base

Conclusions

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Outline

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Paving industry are constantly seeking sustainability: Improve pavement performance, increase construction

efficiency, conserve resources and advance environmental stewardship

Innovations are continuously being developed

Unique engineering challenges in Alaska - extreme climatic conditions and unavailability of quality materials locally in some rural areas

Material properties are limited for mechanistic-empirical pavement design

Background

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WMA demonstration in Petersburg, Alaska

Sasobit was added to reduce the mixing and paving temperatures

Paved ~ 8 miles of road and a new ferry terminal parking lot

Placed in a single 3” lift

Warm Mix Asphalt (WMA)

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311 F 230 F

Sasobit WMA additive

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One year later

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3 different Sasobit contents (0.8%, 1.5%, and 3% by weight of binder PG 58-28)

Binder characterization Viscosity (RV), binder performance grade (DSR,

BBR, DTT), low temperature performance (BBR, DTT, ABCD)

Mixture characterization Dynamic modulus, rutting performance (flow number

and APA), low temperature performance (IDT creep stiffness and tensile strength), moisture susceptibility (TSR ratio)

Characterization of WMA Binders and Mixtures

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Binder Testing Results

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5

AMPT and Rutting

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Flow number and microstrain

Asphalt Pavement Analyzer and Rutting

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6

Moisture Sensitivity

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Low Temperature Performance

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0

1

2

3

4

5

6

7

8

9

10

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

Temperature (oC)

Stre

ss a

nd S

tren

gth

(MPa

)

Control_Stress Control_Strength

0.8S_Stress 0.8S_Strength

1.5S_Stress 1.5S_Strength

3.0S_Stress 3.0S_Strength

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Engineering benefits over conventional HMA Reduced mixing and compaction temperatures

Improved workability and rutting resistance

Insignificant effect on moisture susceptibility

Insignificant effect on resistance to low temperature cracking A decrease of tensile strength for WMA mixtures at low

temperatures

Cracking temperatures of WMA mixtures increased with the increase of Sasobit content. However, the increase was very slight

WMA - Summary

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Recycled Asphalt Pavement (RAP)

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Economic and environmental benefits of using RAP have been acknowledged and high RAP content is promoted

In Alaska, 15% RAP is allowed in the wearing course, up to 25% RAP in the binder or base course. Engineering properties of RAP mixtures are lacking.

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Materials Materials collected in two ADOT regions (Central and

Northern), up to 35% RAP by weight, two mix types (Type II-A and Type II-B), three asphalt binders (PG 52-28, PG 58-34 and PG 52-40)

Performance tests Mix dynamic modulus values at different temperatures,

used in pavement design/analysis procedures (|E*|)

Rutting performance at intermediate and high temperatures (flow number)

Low-temperature thermal cracking performance (IDT creep stiffness and strength)

Materials and Performance Tests

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Dynamic Modulus (lE*l) Master Curves

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Central Region Northern Region

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Flow Number

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Central Region Northern Region

IDT Strength Results

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Northern Region Central Region

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Low Temperature Performance

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‐27.4 ‐27

‐36.9

‐31.8

‐28.4 ‐27.9

‐40

‐35

‐30

‐25

‐20

‐15

‐10

‐5

0

Cracking Temperature (°C)

Central Region

‐23.3‐24.9

‐22.8

‐41.9

‐37.1

‐45

‐40

‐35

‐30

‐25

‐20

‐15

‐10

‐5

0

Cracking Temperature (°C)

Northern Region

Preliminary Cost Analysis

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Incorporation of RAP increased dynamic modulus and flow number of HMA, indicating the addition of RAP may improve the rut-resistance of HMA in Alaska

IDT strength results did not follow a general trend when temperature varied

Adding certain amounts of RAP may not affect the low temperature performance of some mixes

A rough estimate of $13.3/ton savings can be reached if a 25% RAP is used

RAP - Summary

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Multiple benefits of using paving interlayers in AC overlays have been recognized: waterproofing control against infiltration of free surface

water into base and subgrade

retarding of reflection of existing cracks and distresses

How it functions in Alaska and which interlayer type works best are unknown

Paving Interlayers

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PGM-G50/50Bi-axial, two-yarn

PGM-G100/100Bi-axial, three-yarn

PGM-G4

Multi-axial

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Shear Test

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Permeability Test

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ASTM PS 129-01

Maximum acceptable permeability, 125×10-5 cm/s

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Pavement Structural Analysis

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AKFPD - Alaska Flexible Pavement Design

FEM Simulation

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Model configuration

Meshed model

G50/50 (bi-axial)

G4 (multi-axial)

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FEM Simulation Results

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Distribution of tensile stress

G50/50 (bi-axial)

G4 (multi-axial)

FEM Simulation Results

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Field Evaluation

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Field Evaluation Results

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SectionTransverse crack (#)

Longitudinal crack, NB (ft)

Longitudinal crack, SB (ft)

Control (area 4)

Previous1

7 minor300 medium-major

13 minor0

New24 minor 4 medium-major 0

Total11 minor

304 medium-major13 minor

0

G4 (areas 2 & 3)

Previous 8 minor 63 minor 14 minor

New 2 minor 14 minor 0

Total 10 minor 77 minor 14 minor

G50/50 (area 9)

Previous 1 major 78 minor 60 minor

New 0 0 20 minor

Total 1 major 78 minor 80 minor

G100/100 (area 10)Previous 1 major 0 0

New 0 0 0

Total 1 major 0 0

1 Previous−Data collected in May 2015; 2 New−Data collected in June 2016.

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Laboratory investigation confirmed the benefits of adding a paving interlayer

Pavement structural analysis showed fatigue resistance of reinforced was higher than control

G100/100 reinforced showed the highest fatigue resistance, G4 ranked 2nd

FEM analysis revealed G4 reinforced had more effective stress distribution and less maximum tensile strain than G50/50 reinforced

All interlayer-reinforced test sections showed better pavement performance than the control

Paving Interlayer - Summary

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Asphalt concrete (AC)

Granular base

Asphalt treated base (ATB) Hot asphalt treated

Emulsion treated

Foamed asphalt treated

RAP treated base (50%:50% blend)

Current AKFPD Default values available only to three seasons

Only one binder content is considered for ATB

Data required for emerging materials and technologies

Alaskan Materials for Pavement Design

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Limitations of AKFPD Design Guide

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Table 5.1: Pavement Layer Moduli (ksi)

Summer

Material Type P200 Spring & Fall Winter

Asphalt Concrete - 755 510 1500

Aggregate Base < 6% 45 50 100

Select A < 6% 25 35 90

Select B < 10% 15 30 80

Select C & Subgrade < 30% 50 10 10

Stabilized Base Course Moduli (ksi)Summer

Material Spring & Fall Winter

RAP (50:50) (1) 80 80 115

CAB, 3% Emulsion(1) 75 75 115

CAB, 4% Asphalt(2)250 250 1500

(1): lightly-bound: use Ullidtz

(2): heavily-bound: use TAI

AC – dynamic modulus (|E*|) Materials collected from 21 projects across Alaska

All three ADOT regions covered

Granular base – resilient modulus (MR) Fines content ( 3.15% - 12%)

Temperature (-10ºC – 20ºC)

Moisture content (OMC±2%)

Freezing temperature gradient (low – high)

ATB – MR

Three binder contents for each ATB

MR test conducted at three temperatures

Characterization of Alaska Materials

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18

Characterizing |E*| Using AMPT

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Characterizing MR Using Triaxial Test Setup

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19

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Direct Measurement of AC | E*|

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AC | E*| Prediction - Original Witczak Model

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AC | E*| Prediction - Modified Witczak Model

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Predicted vs. measured |E*| for all mixes (original Witczak model, Level 3)

Predicted vs. measured |E*| (modified Witczak model, Level 3)

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MR Modeling for Granular Base

fc = fines content (%), Ws = moisture content (%)

RM 2 3

1 1

k k

octa

a a

k pp p

1 2.54 0.0537* 0.3256* 0.0073* *c s s ck f W W f

2 1.04 0.0354* 0.1070* 0.0071* *c s s ck f W W f

3 2.19 0.0154* 0.4436* 0.0049* *c s s ck f W W f

1 6.59 1.185* 1.111* 0.197* *c s s ck f W W f

2 0.78 0.241* 0.966* 0.118* *c s s ck f W W f

2 5.71 0.927* 1.551* 0.233* *c s s ck f W W f

Free water uptake was allowed during freezing

No water intake occurs during freezing

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Predicted vs. Measured MR

Open system

Close system

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Measured at 20oC, representing summer.

HATB, R2= 0.9074

MR of ATBs

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EATB, R2=0.8327

3.7512 0.063918 · 0.028068· 0.009031 · 0.204352

· 0.01575 ·1

3.78275 0.0517103 · 0.0134

· 0.00596 · 0.107335 ·

0.400538 ·1

FATB, R2=0.8902

MR of ATBs

RAP, R2=0.9265

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4.13 0.0378 · 0.334 ·

0.076 · 0.0553 · 5.29 ·

0.024 · · +0.196 ·

· 0. . 056 · ·

1.58 0.122 · 0.0166 ·

0.411 · 0.375 ·1

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A number of sustainable materials (WMA, RAP, paving interlayers) have been used in Alaskan pavements A number of engineering benefits of Sasobit-modified

WMAs were identified over conventional HMA

RAP mix improved rutting resistance, and adding certain amounts of RAP may not affect the low temperature performance of some Alaskan mixes

Improved performance were confirmed by adding paving interlayers, and the multi-axial paving interlayer had more effective stress distribution than traditional bi-axial interlayer

Conclusions

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Typical Alaska paving materials have been characterized to provide inputs for mechanistic-empirical pavement design

Explore more emerging materials and technologies (different WMA techniques, higher RAP contents, and more paving interlayer types, etc.)

Build up long-term performance data and evaluate potential environmental impacts

Life cycle cost assessment

Conclusions

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