View
3
Download
0
Category
Preview:
Citation preview
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…
Recommended