Bonded Concrete Overlays of...Bonded Concrete Overlays of Asphalt Pavements (BCOA) Presenter: Julie Vandenbossche, Ph.D., P.E. University of Pittsburgh B C O A University of Pittsburgh

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-

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.

2


Definition

• Whitetopping or BCOA - Bonded concrete overlays of existing HMA surfaces.

(Typically 3 – 6 in thick for highways)

HMA pavement Composite pavement

or

3


How can this thin overlay

possibly meet these design

expectations?????

4


Bonded Unbonded

Compression Tension 0

NA

Compression Tension

0

NA

NA

1. Bonded Vs. Unbonded

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2. Slab size

Stresses due to gradients with slab length

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Negative ΔT Positive ΔT


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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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

8

12 ft

12 ft


Purpose

• Increase structural capacity

• Eliminate surface defects

• Improve surface friction, noise and rideability

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Suitable candidates

Adapted from CP Tech Center Overlay Guide

X

Good Candidate

Poor Candidate

10


Suitable candidates

REPAIRS

Good Candidate

Adapted from CP Tech Center Overlay Guide 11


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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Suitable candidates

Corrugations

Slippage

Rutting

Fatigue Block

Top-down cracking

Temperature

Cracking

13


Review design criteria….

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Corner breaks

Dashed Lines Indicate

Location of Wheelpath.

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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


Longitudinal & diagonal cracks

Cell 60

Initiation point

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Traffic Traffic

12’ 12’ 12’

Shoulder

Shoulder

Longitudinal joint spacing

Corner breaks

Long. cracks

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3.7 m 3.7 m


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….


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.

University of Pittsburgh Department of Civil and Environmental Engineering 21


HMA stiffness

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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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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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Composite k-value

Composite

k-value

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Existing Structure – Transverse Cracking

Does the existing pavement

have transverse cracks?

Yes

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Existing Structure – Transverse Cracking

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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/


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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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


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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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


million ESALs

0.3%

cracks

BCOA-ME CDOT

Design hPCC, in 4.5 8.0*

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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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Construction

Finish

Apply curing compound

Use curing practices

Saw joints to depth of T/3

Seal joint

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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/

Documents

Bonded Concrete Overlays of...Bonded Concrete Overlays of Asphalt Pavements (BCOA) Presenter: Julie Vandenbossche, Ph.D., P.E. University of Pittsburgh B C O A University of Pittsburgh