bonded concrete overlays of...bonded concrete overlays of asphalt pavements (bcoa) presenter: julie...
TRANSCRIPT
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University of Pittsburgh Department of Civil & Environmental Engineering
Bonded Concrete Overlays of
Asphalt Pavements (BCOA) Presenter:
Julie Vandenbossche, Ph.D., P.E.
University of Pittsburgh
C O A B University of Pittsburgh
North Carolina Concrete Pavement
Conference Concord, North Carolina
-October 28, 2014-
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University of Pittsburgh Department of Civil and Environmental Engineering
Acknowledgments
• FHWA Pooled Fund Study TPF 5-165: Iowa, Kansas, Minnesota, Missouri, Mississippi, New York, Texas, Pennsylvania, and North Carolina Departments of Transportation
OBJECTIVE:
Develop a BCOA design procedure that is spreadsheet based but has a framework that can be incorporated in to the AASHTO Pavement ME.
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University of Pittsburgh Department of Civil and Environmental Engineering
Definition
• Whitetopping or BCOA - Bonded concrete overlays of existing HMA surfaces.
(Typically 3 – 6 in thick for highways)
HMA pavement Composite pavement
or
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University of Pittsburgh Department of Civil and Environmental Engineering
How can this thin overlay
possibly meet these design
expectations?????
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University of Pittsburgh Department of Civil and Environmental Engineering
Bonded Unbonded
Compression Tension 0
NA
Compression Tension
0
NA
NA
1. Bonded Vs. Unbonded
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University of Pittsburgh Department of Civil and Environmental Engineering
2. Slab size
Stresses due to gradients with slab length
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Negative ΔT Positive ΔT
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University of Pittsburgh Department of Civil and Environmental Engineering
3. One wheel per slab
Thickness 2 to 6 in
Slab size 1×1 ft, 3×3 ft, 4×4 ft
and 6 × 6 ft
One wheel
per slab
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University of Pittsburgh Department of Civil and Environmental Engineering
4. Slab size
12 ft
12 ft
½ Axle Load per Slab Full Axle Load per Slab
More fully supported
Lower stress
Reduced support
Higher stress
Top View
Front View
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12 ft
12 ft
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University of Pittsburgh Department of Civil and Environmental Engineering
Purpose
• Increase structural capacity
• Eliminate surface defects
• Improve surface friction, noise and rideability
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University of Pittsburgh Department of Civil and Environmental Engineering
Suitable candidates
Adapted from CP Tech Center Overlay Guide
X
Good Candidate
Poor Candidate
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University of Pittsburgh Department of Civil and Environmental Engineering
Suitable candidates
REPAIRS
Good Candidate
Adapted from CP Tech Center Overlay Guide 11
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University of Pittsburgh Department of Civil and Environmental Engineering
Suitable candidates
• Good Candidate:
• Stable support conditions (Localized weak areas can be strengthened)
• Surface distresses
• Min. of 3 mm of HMA remaining after milling
• Poor Candidate:
• Significant structural deterioration
• Significant stripping of HMA layers
• Poor drainage
• Inadequate or uneven support conditions
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University of Pittsburgh Department of Civil and Environmental Engineering
Suitable candidates
Corrugations
Slippage
Rutting
Fatigue Block
Top-down cracking
Temperature
Cracking
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University of Pittsburgh Department of Civil and Environmental Engineering
Review design criteria….
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University of Pittsburgh Department of Civil and Environmental Engineering
Corner breaks
Dashed Lines Indicate
Location of Wheelpath.
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University of Pittsburgh Department of Civil and Environmental Engineering
Traffic Traffic
12’ 12’ 12’
Shoulder
Shoulder
1.8x1.8m Panels
1.2x1.2m
Panels
2’ x 2’
Panels
3’ x 3’
Panels
0.6x0.6m
Panels
1x1 m
Panels
Shoulder
Shoulder
Longitudinal joint spacing
Corner breaks
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3.7 m 3.7 m
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University of Pittsburgh Department of Civil and Environmental Engineering
Longitudinal & diagonal cracks
Cell 60
Initiation point
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University of Pittsburgh Department of Civil and Environmental Engineering
Traffic Traffic
12’ 12’ 12’
Shoulder
Shoulder
Longitudinal joint spacing
Corner breaks
Long. cracks
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3.7 m 3.7 m
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University of Pittsburgh Department of Civil and Environmental Engineering
Design Options
Small slabs
(< 4.5 ft)
Midsize slabs
(4.5 to 6 ft)
1. Corner Breaks
1. Long. Cracks
2. Diagonal Cracks
Larger slabs
(10 to 12 ft)
1. Long. Cracks (Midslab)
2. Long. Cracks (whlpth)
3. Transverse Cracks
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1. BCOA - ME.
2. ACPA BCOA App
1. BCOA-ME
1. BCOA - ME
2. CoDOT
< 6
.5 in
Failure Mode Panel size Design Procedure Panel
Thickness
> 6
.5 in
Full lane
width
1. Transverse Cracks Conventional design
1. AASHTO ’93
2. Pavement ME
3. Etc….
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University of Pittsburgh Department of Civil and Environmental Engineering
Design Options (Composite pavements)
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HMA< 4 in - Unbonded Overlay
Conventional unbonded overlay design
1. AASHTO ‘93
2. AASHTO Pavement ME
3. etc…
New procedure (coming soon)
HMA>4 in - Bonded Overlay
BCOA-ME
Possibly CoDOT or ACPA BCOA app.
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University of Pittsburgh Department of Civil and Environmental Engineering 21
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University of Pittsburgh Department of Civil and Environmental Engineering
HMA stiffness
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University of Pittsburgh Department of Civil and Environmental Engineering
HMA stiffness
HMA condition
Fatigue cracking (%)
Damage factor
EHMA reduction (%)
Adequate 0 – 8% 0.4 10 Marginal 8 – 15% 0.6 20
Establish EHMA
1. Estimated EHMA for new mix
• Binder selected based on geographical location &
LTPP Bind
• Typ. agg. gradation
2. Adjust EHMA
• Aging
• Fatigue - % HMA fatigue cracking
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University of Pittsburgh Department of Civil and Environmental Engineering
Existing Structure: k-value
HMA Pavement
E= HMA
kcomposite = All granular layers
1. No bond @ old HMA/old PCC interface
E= HMA
kcomposite = old PCC + All granular layers
2. Bond @ old HMA/old PCC interface
E= HMA + old PCC
kcomposite = All granular layers
Composite Pavement
kcomposite
E
kcomposite
E
kcomposite
E
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University of Pittsburgh Department of Civil and Environmental Engineering
Composite k-value
Composite
k-value
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University of Pittsburgh Department of Civil and Environmental Engineering
Existing Structure – Transverse Cracking
Does the existing pavement
have transverse cracks?
Yes
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University of Pittsburgh Department of Civil and Environmental Engineering
Existing Structure – Transverse Cracking
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University of Pittsburgh Department of Civil and Environmental Engineering
BCOA-ME design guide
http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/
….or Google BCOA ME
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http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/
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University of Pittsburgh Department of Civil and Environmental Engineering
Design example: 6ft x 6ft
Design ESALs, million 4.8
Location: Cell 95, MnROAD
Minneapolis, MN hHMA, in 10
HMA condition Fair
Comp. k- value, psi/in 150 Traffic
Existing structure
MOR, psi 650
CTE, 10-6 in/°F/in 4.8
PCC properties
Without structural fiber
Design Comparisons
Agency design and performance
Built-in hPCC, in 3.0
Distress @ 7 years, 4.8
million ESALs 20% cracks
Design output Pitt CDOT
Design hPCC, in 4.0 0.5*
Calculated hPCC, in 4.04 0.5*
* Indicates design minimum
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University of Pittsburgh Department of Civil and Environmental Engineering
Design example: 6ft x 6ft
Design ESALs, million 4.8
Location: Cell 95, MnROAD
Minneapolis, MN hHMA, in 10
HMA condition Adequate
Comp. k- value, psi/in 150 Traffic
Existing structure
MOR, psi 650
CTE, 10-6 in/°F/in 4.8
PCC properties
Structural fiber: Polyolefin, 25lb/cy
Design Comparisons
Agency design and performance
Built-in hPCC, in 3.0
Distress @ 7 years, 4.8
million ESALs 20% cracks
Design output Pitt CDOT
Design hPCC, in 3.0* 0.5*
Calculated hPCC, in 2.65 0.5*
* Indicates design minimum
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University of Pittsburgh Department of Civil and Environmental Engineering
Design example: 6ft x 6ft
Design ESALs 0.3 million
Road cat. Collector
One-way ADT 1,050
Location: Highway-2,
Cumberland County, Illinois
hHMA, in 3.5
HMA condition Adequate
Comp. k-value, psi/in 170
Traffic
Existing structure
MOR, psi 650
CTE, 10-6in/°F/in 3.8
PCC properties
Design Comparisons
Design output As-built design and performance
As-built hPCC, in 5.75
Distress @ 3 years, 0.08
million ESALs
0.3%
cracks
BCOA-ME CDOT
Design hPCC, in 4.5 8.0*
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University of Pittsburgh Department of Civil and Environmental Engineering
Construction
Milling enhances bond (especially for overlays < 4 in)
Milling depth required o Remove surface distortions > 2 in deep
o Match curb or adjacent structure elevations
o Meet min. vertical clearance
o Correct cross slope changes for in surface layer
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Construction
Clean surface
oSweeper
oCompressed air
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Construction
Mist surface
o Reduces surface temp.
o Reduces moisture absorption from concrete mix
Place concrete
Paver
Clarey screed
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University of Pittsburgh Department of Civil and Environmental Engineering
Construction
Finish
Apply curing compound
Use curing practices
Saw joints to depth of T/3
Seal joint
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University of Pittsburgh Department of Civil and Environmental Engineering
Thank You
Any Questions?
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….or Google BCOA ME
http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/