Reflective Crack Relief Interlayers

by

Bill Buttlar

University of Illinois at Urbana-Champaign

Cracking in Pavements Symposium – Laramie, WYJuly 19, 2007

Acknowledgements Glaucio Paulino

Phil Blankenship

Imad Al-Qadi

Mike Wagoner

Seong Song

Eshan Dave

Hyunwook Kim

Diyar Bozkurt

National Science Foundation

SemMaterials, L.P.

Illinois Department of Transportation

Illinois Division of Aeronautics

Research Motivation

Motivation:Asphalt Overlays are an Attractive Rehabilitation Alternative:

• Rapid Placement• Economical• Excellent Smoothness, Skid

Resistance, Markings Contrast

Asphalt Overlay life is often cut short due to Reflective CrackingSome Interlayer treatments show promise, but difficult to predict, esp. for LCCAMechanisms of Cracking Not Well Understood

4

Reflective Cracking

Mechanisms

- Temperature Related - Load Related

- Thermo-Mechanical (elements of both)

5

Recent Reflective Cracking Studies at UIUC

Cost-Effectiveness of Reflective Crack Control Treatments in Illinois (1996-1999 and 2005-2008)

Rantoul National Aviation Center (1999-2001)

Greater Peoria Regional Airport (2000-2002)

NSF GOALI Study (2002-2006)

6

Scope of Presentation

Lessons Learned from Previous Studies:Construction Issues and Best PracticesPerformance ObservationsLife Cycle Cost Analysis (LCCA) Findings

NSF GOALI StudyNew Fracture Tests and Modeling ToolsField ProjectsInsights Towards RC Mechanisms

Focus on:HMA placed over PCCSelected Fabrics and Reflective Crack Relief Interlayers

Cost-Effectiveness of Paving Fabrics to Control Reflective

Cracking

By

William G. ButtlarDiyar Bozkurt

Barry J. DempseyIDOT ITRC Study, 1996-1999

8

Fabric InstallationArea-Wide Treatment

9

ITRC Study Tasks

Identify Projects Using Strip and Area TreatmentsProjects with Control Sections Highly Desired

Identify Projects Eligible For But Not Receiving Treatments

Evaluate Performance

Assess Cost Effectiveness

Evaluate/Revise Policy

10

Fabric Cost vs. Project Size

0

0.2

0.4

0.6

0.8

1

0 100000 200000 300000Quantity of Fabric (ln. ft.)

Cos

t ($/

ln. f

t.)

Avg = $0.51/ln ft

Avg = $0.30/ln ft

Avg = $0.23/ln ft

Strip Treatment

11

Transverse Cracking (Number of Cracks/500 ft)

0102030405060

0 10 20 30 40 50 60Untreated

Treated

All Area Treated

7

9

3

3

32

Age (yrs.)

12

Predicting Number of Years to RehabilitationStrip Treatment - 26 Projects

1

3

5

7

9

0 5 10 15 20Years

CR

S

95% Confidence Intervals

12.9 years

Rehabilitation Trigger Level = 5 10.5

Years11.5Years

13

Estimated Life Span

0

5

10

15

2095% Confidence

Interval

Years

Strip ControlArea

14

LCCA Results

0

2000

4000

6000

8000

10000

Strip Treatment Area Treatment Control Section

Equi

vale

nt U

nifo

rm

Ann

ual C

ost (

$)

15

EUAC Comparisons Relative to Untreated Projects

-15.0

-5.0

5.0

15.0

Perc

ent C

hang

e in

EU

AC

Rel

ativ

e to

C

ontr

ol

Strip Area

Small ProjectSize

Medium ProjectSize

Large ProjectSize

Not Cost Effective

Cost Effective

16

Permeability Test

17

Permeability Testing Results

-5

15

35

55

75

95

IL 9 (AreaTreatment)

IL 251 (AreaTreatment)

IL 176 (StripTreatment)

Perm

eabi

lity

(ml/m

in)

0

Area-Wide Fabric May Provide Waterproofing after Reflective Cracking Occurs, Unless PCC Joint is Severely Deteriorated

Rantoul RC Study - Background

Chanute AFB - Built 1940’s

(WWII)

JCP - 6” to 8” on Subgrade

Closed 1971, Reopened in

1993 as GAA - Rantoul NAC

Rantoul National Aviation Center

ATREL, 1/4 mi.

Rehabilitation TechniquesTo Prevent Reflective Cracking

Rubblization (Three Breaking Patterns)

Interlayer Stress Absorbing Composite (ISAC) High

Strength/ Strain Tolerant Interlayer Material

Saw and Seal

Polymer-Modified Overlay

Testing

DCP FWD

Rubblization – Summer of 1999

Multiple-Head Breaker Z-Grid Roller

Breaking Patterns

Fine - 3” Max Medium - 9” Max

Breaking Patterns

Coarse Break Pattern - 18” Max

Joint Movement Sensors

Horizontal Vertical

Blow-ups, Course Rubblization

Interlayer Stress Absorbing Composite(ISAC)

ISAC, Close-up View

Temperature Data

Seasonal Joint OpeningHighly Correlated with Seasonal Temperature

Daily Joint Movement Also Monitored

Joint Movement

Sensor Response to

Dynamic Loads

Saw and Seal – Sealant DamageAfter Second Winter

Inadequate Coverage

of Backer Rod is Observed

No Load = No Reflective Cracking (soft binder used)

Rantoul SummaryRubblization Over Marginal Soils was Successful

Fine Break Pattern is Recommended Whenever Possible

Coarse Break Section Developed Mild Blowups

ISAC Appeared to Reduce Damage to Overlay During Construction

Pavement Sensors Are Providing Valuable Inputs:

Will Factor in Performance Assessment

Development of Models and Mechanistic Design Procedures

Due to Low Number of Departures and Light Aircraft, Differences

between Treated and Control Sections are not yet Discernable (Zero

cracking after 7 years)

34

IDOT RC Study – US 136 Section

35

IDOT RC Study – Fabric Section

Stripping Observed

36

Cracking Development - Fabric

37

Typical STRATA-Type SAMI

Surface Course

Binder Course

Existing Jointed PCC Pavement

1.00-in.(24 mm)STRATA

RC Potential

Fracture-Resistant Interlayer

Typical HMA – Moderate to Low Fracture Resistance

38

US 136 - SAF Section

SAF layer

Wearing surface

Pre-existingoverlay

NSF GOALI* Study

0%

20%

40%

60%

80%

100%

March,2001

Feb,2002

April,2003

Feb,2004

Aug,2005

Strata SystemControl

*Grant Opportunities for Academic Liaison with Industry

Research Motivation - CollaborationThe Strata Interlayer Mix has Unique

Creep and Fracture Properties and Many

Field Installation Locations, but a

Mechanics-Based Design Model is

Currently Not Available

UIUC Researchers Have Cutting Edge

Testing and Analysis Capabilities, esp. in

Fracture

The NSF GOALI Program, Partners

Academia w/ Industry to Advance

Knowledge in Science and Engineering25 mm

Strain-Tolerant Interlayer

41

Integrated Approach

FieldPerformance

LabTesting

ComputerSimulation

Re-calibration (if necessary) and

validation

1

2

Verification, calibration (if

necessary) and validation

HMA OverlayPCC

Interlayer

42

Notched-Beam Fracture Test (SE(B))

Crack Mouth Opening Gage is Used for Closed-Loop Control

Wagoner, M. H., Buttlar, W. G., and G. H. Paulino, “Development of a Single-Ended Notched Beam Test for Fracture Testing of Asphalt Concrete,” ASTM Journal of Testing and Evaluation, Vol. 33, No. 6, JTE12579, Nov. 2005.

43

Load-CMOD Curves

-10 oC

0 1 2 3 4 5 60

1

2

3

4

5

6

7

CMOD (mm)

Lo

ad (

kN)

9.5mm PG64-22STRATA

44

Disadvantage of SE(B)

14.75”

4”

3”

?

45

Challenge: Material Properties from Thin Specimens

Material Properties from Experiments on Thin, Cylindrical Shaped Specimens

Collection of Materials

Computational Simulations

Pavement Cracking

46

Fracture Energy

Needed to develop simple yet reliable tests to obtain fracture energy (Gf) Provide data for calibration of cohesive zone fracture model

Gf

CMOD

Load

Quasi-brittle fracture

Softening

47

Disk-Shaped Compact Tension (DC(T))

Fracture Plane

IDT Specimen DC(T) Specimen

Can be Obtained from Field Cores

Wagoner, M. P., Buttlar, W. G., and G. H. Paulino, “Disk-Shaped Compact Tension Fracture Test: A Practical Specimen Geometry for Obtaining Asphalt Concrete Fracture Properties,” Experimental Mechanics, Vol. 45, No.3, pp. 270-277, June, 2005.

48

DC(T) Testing

Above: Clip Gage Mounted onto Knife-Edge Gage Points

49

DC(T) Testing

50

Load-CMOD Curves

-10 oC

0 1 2 3 4 5 60

1

2

3

4

5

6

7

CMOD (mm)

Lo

ad (

kN)

9.5mm PG64-22STRATA

51

Superpave Indirect Tensile Test (IDT)

Diameter: 150 or 100 mmThickness: 0.2D to 0.65D4 displacement sensors:

2 horizontal2 vertical

Gage length:38.1 mm (150 mm diameter)25 mm (100 mm diameter)

PropertiesCreep ComplianceTensile Strength

Displacement Sensors

52

Load

Deflections

Creep Compliance Testing

10-1

100

101

102

103

10410

-2

10-1

100

101

Time (sec)

-30 oC-20 0C-10 0C

Com

plia

nce

(1/G

Pa)

53

E* from Cylindrical Specimens

IDT E* Test

(Can be Used on Specimens as Thin as 19mm)

Typical E* Test

(Not Suitable for Field Cores, Which

Have Thin Lifts)

54

Which Test is Most Important?

Design vs. ForensicsNature of MixNature of Design Application

ClimateTrafficPavement Structure

Often, the Entire Testing Suite is the Safest and Most Comprehensive Approach

CreepE*CTEFracture

55

Fracture Energy – UIUC IDOT RC Study 2006

Comparisons of Fracture Properties

0

200

400

600

800

1000

1200

1400

1600

1800

2000

IL130NIUS136EW IL29CC

US136WIIL130SN

IL29MO MatBDIL29CH

IL130SIUS136EI

Frac

ture

Ene

rgy

(J/m

2 )

25

30

35

40

45

50

55

60

65

70

Nor

mal

ized

Pea

k Lo

ad (k

N/m

)

Fracture Energy (J/m2)Peak Load (kN/m)

PMACSAF4.75 mm

w/ PG 76-28

Fracture Modeling and Simulation in NSF GOALI Research

Glaucio Paulino, Seong H. Song, and Bill Buttlar

57

Cohesive Zone(Fracture) Model

δA

Bt

A

B

Cohesive Zone

Crack TipAB

The Cohesive Zone Model is applicable for both ductile and quasi-brittle materials. A numerical singularity at the crack tip is avoided by prescribing a maximum traction, t, equal to the tensile strength.

DC(T) test

58

3D DC(T) Simulation

59

Mode-Mixity in Pavements

Existing Pavement

SE(B) test is versatile and unique: a relatively simple test which can be used to investigate mixed-mode fracture behavior in asphalt concrete.

Offset Notch

60

Mixed-Mode Fracture TestCenterline

γ S/2

Crack Detection

Gages

Increasing shear as offset (γ S/2) increases (S = Span Length)

Competition between tensile stress at centerline and mixed-mode stress at notch tip

61

Mixed-Mode FE Simulation with CZM

Cohesive elements are inserted over region 3

# of bulk elements: 5398 T3

# of cohesive elements: 3066 4-node-linear

Length of cohesive elements is around 1.0 mm

1 Region: 12 23

62

Animation of Mixed-Mode SE(B)

Department of Civil and Environmental Engineering

University of Illinois at Urbana-Champaign

Field Investigation of Pavements for NSF GOALI Study

Bill Buttlar, Glaucio H. Paulino, Eshan Dave

64

Project Locations (Climatic)

65

IA9 Interlayer Section 3 – 2D Modeling

66

IA-9, Control Section, 3D Model

67

Cooling Cycle Simulation – No cracking

SofteningSoftening

-3 -2 -1 0 1 2 3

TensionTensionCompressionCompression

(Stress, MPa)

Surface Course

Binder Course

Lev1 Course

Lev2 Course

68

Crack Jumping Mechanism Under Heavy Loads

Interlayer Treated Section

Softening

Cracking

Binder Course

Surface Course

Interlayer

Old AC/PCC

Subgrade

AC Layers

69

Key Modeling Findings

Strain-tolerant interlayers can have significant factor of safety against fracture, even under severe thermal and traffic loadingInterlayers can significantly lower strain in HMA overlays (relative to control sections)However, traditional HMA overlays may be too brittle to withstand residual strainsRecommendations – Use improved surface layers (SMA, polymer modified) in conjunction with interlayers for best performance of overlay

70

Summary of Lessons Learned

For GA Airports with Light Loads, Stress Absorbing Interlayers can be very Effective in Preventing Reflective Cracking, Even in Cold ClimatesNon-Woven Fabrics in Illinois were Found to be Marginally Cost EffectiveThick, High Fracture Energy Interlayers Delay Reflective Cracking Onset, Lessen Crack Severity, Distribute (Offset Cracks). Cost Effectiveness needs to be Quantified.

71

Summary of Lessons Learned (cont.)

Recommendations for Interlayer Implementation – Use improved surface layers (SMA, polymer modified) in conjunction with Interlayer for best performance of overlay systemFull-scale validation of new designs needed (will also help modeling)Simplified Fracture Energy Test (DC[T]) Apparatus is needed

72

What’s next ? ATLaS Testing

Existing CRCP Test Lanes

Proposed 500-ft Testing Lane

ATREL(Advanced TransportationResearch andEngineeringLaboratory)

Study Crack Mechanisms and Mitigation Strategies for HMA Overlay Systems

73

Advanced Testing and Loading System (ATLaS)

74

HMA over PCC – Thermal Reflective Cracking

PCC-1 PCC-2 PCC-3 PCC-5PCC-4

x

Design of Full-Scale Testing Section for Reflective Cracking StudyThermal Cracking Simulations

PG64-22 Binder (AC-20 or PEN 60-70)Flexible Pavement Structure – No Cracking PredictedComposite Pavement Structure – Thermal Cracking Predicted (same binder/mixture)Softer binder (PG 58-28) – No cracking predicted

75

Multi-Scale Discrete Element Pavement Modeling is Now Possible

Local responses in area of interest properly considered

Homogenized Properties Considered Elsewhere for Model Efficiency

Subgrade

Base

PCCAC

Micro- & Macro-Cracks

Tire Loading

76

Thank You !!!

Questions…Discussion…