concrete pavement overlays

7/27/2019 Concrete Pavement Overlays

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Concrete Pavement Overlays

36th Annual Mid-Atlantic QualityAssurance Workshop

Charleston, WV

February 12, 2003

Robert R. Long Jr.Regional Director

American Concrete Pavement Association

Northeast Chapter


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Family of Concrete Overlays

BondedConcrete

Overlay

UnbondedConcrete

Overlay

Existing PavementConcrete

ConventionalWhitetopping

Overlay

Ultra-ThinWhitetopping

Overlay

ConcreteOverlays

Existing PavementAsphal t


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Concrete Pavement Types

Jointed Plain

Undoweled

Doweled

Jointed Reinforced

Continuously Reinforced


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Bonded Concrete Overlay

Consists of a thin concrete layer (100 mm or less)on top of an existing concrete surface.

Specific steps are taken to bond the new concreteoverlay to the existing concrete.

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Bond = Strength


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History First bonded PCC resurfacing

Warsaw Street in Toledo, Ohio in 1913.

Used to correct construction deficiencies relating to a frozenpavement.

Typical applications have been:

to correct construction deficiencies to correct surface problems relating to wear or loss of skidresistance

to repair damage caused by chemical spills.

In recent years, used to improve load-carrying

capability where feasible to change the grade.


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Advantages

Increase structural capacity. More efficient than AC.

One in. of PCC ~ two in. of AC

Critical edge stresses are

about 35% lower than an

equivalent asphalt overlay. Long service life

High PSI.

Lower user & engineeringcosts.

Rut free100

140

180

220

260

300

0 2 4 6 8

Overlay Thickness (in.)

Edge

Stre

ss

(psi)

Bonded

PCC Overlay

AC Overlay


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Applicability

Condition of underlyingpavement dictates thefeasibility...

But you must consider pre-overlay repair.

Do NOT apply to appreciably distressed

pavements.

pavements with high-severity"D" cracking or reactive

aggregate problems.


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Pre-Overlay Repair

Not all transversecracks require repair.

Address working

cracks (faulting,pumpingcorner breaks)

Full-depth repair.

Random crack control.

NOTE: Untreated c racks wil l eventual ly ref lect

through . Saw & seal the cracks

Transverse Cracks


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Placed and Tacked Directlyonto Pavement Surface

-OR-Mounted on Chairs

Recessing Bars

2 inches Cover

Milled

Placement of Crack Control Cages


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Placement of Crack Control Cages


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Pre-Overlay Repair

Spalling, blow-ups, cornerbreaks.

Repair Full or Partial Depth

Lightly spalled joints may be

milled to sound concrete. Depressions less than 2 in. deep,

fill with concrete during the overlay

operation.

Depressions more than 2 in. deep,

fill with concrete prior to the

overlay.

Joint Deterioration


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Bonding

Bonding between the two layers isprincipally a mechanical process

Depends primarily on the soundness and

cleanliness of the underlying pavement. Full Bond

Bond shear strength = 200 psi (min.)

Is grout required to enhance bonding?


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Cleanliness is key to long-term performance.

Surface preparation procedures:

Shotblasting

Milling

Surface Preparation


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Shotblasting


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Bonded Overlays

Milling


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Bonded Overlays

Milling

Shotblasting


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Bonded Overlays

SurfaceCleaning


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0

100

200

300

400

500

600

ShearStren

gth(psi)

Milled/Grout Milled/None Shot

blast/Grout

Shot

blast/None

Corner Center Edge Average

Grout or No-grout?

Unpublished Research Data: University of Texa


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Curing

Bonded Overlays

Critical because high ratioof surface area to volumeof concrete.

Apply ASAP

1 gallon/100 sq.ft.

Coat all exposed edges.

Avoid extreme weather.

Avoid contact with

prepared surfaces.


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Good when:

Placed correctly and at the right time.

Poor when: Placed on deteriorated pavements.

Loss of bond does not necessarilyconstitute failure.

Performance


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Early Performance Studies

Gillette 1965 Included 10 overlays placed between 1954 - 1963. Adequate performance can be expected regardless of

the thickness of the resurfacing and the type offrequency of traffic

Gausman 1980 Overlays in seven states, built between 1973 -1975.

Overlays can be effectively bonded to clean pavements ingood condition.

Quality of surface preparation is critical

Bond can be retained without bonding grout.


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Other Performance Studies

Peshkin and Mueller - 1990 Study of 10 thin-bonded overlays constructed between

1976 1985.

Thickness ranged from 2 5 in.

All were jointed resurfacing of jointed original pavement.

Found mixed success.

Some projects failed in relatively few years

Others carried more than the anticipated traffic and were

performing well.


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Unbonded Concrete Overlay

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Consists of thick concrete layer (125 mm or greater)on top of an existing concrete.

Uses a separation interlayer to separate newoverlay and existing concrete.


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Unbonded Overlay

When to Use Unbonded


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When to Use UnbondedOverlays

Little or no remaining structural life

Extensive and severe durability distress

Medium to very heavy truck traffic Very weak or wet subgrade

Other obstacles to reconstruction


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Benefits

Unbonded Overlay

Little pre-overlay repair needed

Improved Structural Capacity. Very Strong Base that can maintain traffic

Reduced Faulting, Pumping, & Loss of Support

Can place on pavement in bad condition. i.e. "D" cracked pavements, ASR, etc.

No future reflective cracking.

Avoids reconstruction problems

Less construction time

What types of UBOLs and existing


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Existing Pavement Type

JPCP JRCP CRCP AC/PCC

JPCP

JRCP

CRCP

What types of UBOLs and existingpavements are compatible?

UBOLType

What types of UBOLs and existing


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Existing Pavement Type

JPCP JRCP CRCP AC/PCC

JPCP JRCP

CRCP

What types of UBOLs and existingpavements are compatible?

UBOLType

Unbonded Overlay


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Unbonded OverlayPreoverlay Repair

Unbonded Overlays are less sensitive to underlying

pavement condition than any other Overlay type

May be needed:

Repair/replace shattered or rocking slabsRepair punchouts in CRCP

Probably not needed:

Repair of other slab cracking

Repair of joint spalling

Load transfer restoration

Unbonded Overlay


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Joint Deterioration

Unbonded OverlayPreoverlay Repair

Remove Loose Materialat Mediumto High Severity Spalls(Cold Milling).

Place Cold Patch if ThinInterlayer.

What about Fracturing the


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What about Fracturing theExisting Slab

If you can fracture anexisting concrete slab and

place an AC overlay

why cant you place an

AC leveling course & an

unbonded PCC overlay?

A few UBOLs of rubblized

PCC have been built

But is the extra expense ofrubblizing justified?

U b d d C t O l


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Allows layers to actindependently.

Prevents distresses fromreflecting into overlay.

Materials that work:

Asphalt concrete

Some surface treatments

Materials that do not:

Polyethylene

Roofing paper

Curing compound

Separation Interlayer:

U b d d O l


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Unbonded Overlays

Can also use existingAC overlay asinterlayer


U b d d C t O l


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Overlay

Old Pavement

Key

Overlay

Old Pavement

Smooth Slip Plane

Thick Interlayer (> 50 mm)


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Whitewash Prevent heat build-up

by reflecting

heat/energy

Temperature reductionas much as 11C

(20F)

Typically lime slurry or

curing compound

U b d d O l


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Jointing

Unbonded Overlays

Mismatch joints.

Saw joints d/3.

3 FT.3 FT.

Overlay joints should bemismatched from working cracks too

U b d d C t O l


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Very Good

Can be expected to perform for 20+ years.

Most failures are due to the use of inadequateseparation layers.

Performance

U b d d C t O l


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NCHRP Synthesis 99, 1983

NCHRP Synthesis 204, 1994

NCHRP Report 415, 1999

Performance

JPC U b d d O l


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0

2

4

6

8

10

12

14

0 20 40 60 80 100

Year Built

UBOLThickn

ess(inches)

Thicknesses and Years Built

No. Projects built = 105

No Projects taken out of service = 4

Avg age when taken out of service = 20.4 yr

JPC Unbonded Overlay

JRC U b d d O l


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0

2

4

6

8

10

12

0 20 40 60 80 100

Year Built

UBOLThickn

ess(inches)




Avg age when taken out of service = 22.8 yr

JRC Unbonded Overlay

CRC U b d d O l


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0

2

4

6

8

10

12

0 20 40 60 80 100

Year Built

UBOLThickn

ess(inches)




Avg age when taken out of service = NA

CRC Unbonded Overlay

Concrete Overlays of Asphalt


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Whitetopping

y p(Whitetopping)

Consists of a thick concrete layer (100 mm or greater)placed directly on top of an asphalt concrete pavement.

Behaves as a new pavement on a strong base.

UTW Whitetopping


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UTW Whitetopping

Whitetopping:

Well-established, proven pavement

rehabilitation technique

Ultrathin Whitetopping:

Newer technology

Still under evaluation by some

Whitetopping History


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Whitetopping - History

First Whitetopping South 7th street in Terre Haute, Indiana - 1918

Existing flexible pavement was overlaid with 3 - 4in. of reinforced concrete

During 40s and 50s -Used to upgrade military & civil airports

Highway use

Started approx. 1960

Types have included JPCP, JRCP, CRCP, FRC

Whitetopping Use by State


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Whitetopping Use by State1992

0

1

2 - 5

6 - 10

11 - 20

> 50NCHRP Report 204

1992

Whitetopping by Pavement Type


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Whitetopping by Pavement Type

85% of projects arejointed, plain concretepavements (JPCP)

CRCP - 7.3%

FRC - 4.5% JRCP - 3.2% N

um

ber

JPCP JRCP CRCP FRC0

20

40

6080

100

120

140

160

JPCP JRCP CRCP FRC

Type of Overlay

Whitetopping Advantages


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Whitetopping - Advantages

Construction

Can place onpavement in badcondition.

Little or no pre-overlayrepair needed.

Avoid reconstructionproblems.

Minimal rain delays.

Maintain traffic on

existing surface.

Whitetopping Advantages


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Whitetopping - Advantages

Improved structural capacity.

Reacts structurally as if on

strong base course.

Maintains high level of

serviceability. Concrete slabs bridge

problems asphalt cannot.

Reduced potential forpumping, faulting

and loss of support.

Structural

Whitetopping Construction


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Critical issue is uniform support Subgrade / base failures need repair

Need to evaluate drainage (esp. Inlays)

Address surface distortions Direct application

Profile milling

Leveling course



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Pre-overlay PreparationOther Factors

Joint Sawing Depth

Cost ComparisonDrainage

Sweep Surface

Crack filler

Repair Performed

None

Milling or Leveling

Milling?

None

None

NoneNone

NoneNone

Distress

Rutting (< 2 in.)

Rutting (> 2 in.)

Shoving

Raveling

Trans. Cracking

Block CrackingAlligator Cracking

Long CrackingBleeding



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Direct Application Sweep surface and place

Use when rutting < 50 mm

On crowned roadways makes

thickened edges

Economical, practical.

Surface cross-section survey.

Determine cross-sectional area

& overlay volume.

Concrete overlay fills ruts.



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Transverse Cracks

Overlay

Old Pavement

Key

Overlay

Smooth Slip Plane

Old Pavement



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Profile Milling Use when rutting > 50 mm

Removes between 25 and

75 mm

Can shave off top of ruts

Used with inlays Limited vertical clearances

Single lane replacement



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Leveling Course Consider only where extreme rutting or

distortion exists

Use when rutting > 50 mm

Places between 25 and 50 mm of AC Can just fill ruts

Requires more equipment, materials, time

Usually most expensive option



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Whitewash


Apply if surface > 110degrees F.

Prevents heat build-up

or Excessive mixtemperatures.

Maintains hard pavingsurface.

Most critical for leveling

course

Whitetopping Overlays


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Joint depth (D/3).

Adjust if vary over 1 inch of nominal thickness.

D

+ 1 inchD/3


Jointing



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Most projects are too new to provide data

Approximately 78 projects before 1982

Over 100 new projects between 1982 and 1992

Used to combat rutting in heavy truck corridors Those that are old enough are providing excellent

performance

Oldest in-service project built 1956(Columbus AFB, Miss.)

Performance



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US 1 - Daytona Beach, FL. Built in 1987

19 test sections -150, 175, 200 mm thick

10 year design

After 14 years service - Excellent Condition

No sign of anticipated early deterioration

High bonding between AC and PCC

AC companion sections have been resurfaced twice

Performance

Inlay Whitetopping Performance


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y pp g

Have had good to poor performance

Poor performance results from:

Poor drainage

Bathtub sections Poor load transfer

Performance



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y pp g

I-5 Portland, Oregon Built between 1971 and

1975

330 mm thick CRCP

Used in truck lanes

Excellent performance

Performance



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y pp g

I-70 Sherman Co., Kansas Built in 1983 and 1985

200 mm thick - No dowels

After about 3 years of service

3 mm of faulting

Some long. cracking, pumping, & corner breaks

Absence of dowels and bathtub section

contributed to distress development

Performance

Ultra-Thin Whitetopping


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pp g

A concrete overlay, 2 to 4 inches thick withclose joint spacing, bonded to the existingasphalt pavement.

May or may not contain fibers

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Performance Evaluation


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Ten UTW projects in Tennessee & Georgia Some of first projects in U.S..

Concrete of similar mixture proportions

Relatively close proximity

Roads of similar use (except one)

Minimal traffic control during surveys

Pavement Condition Index (PCI)


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( )

Numerical Rating from 0 to 100 -- 85-100 Excellent

70-84 Very Good

55-69 Good

40-55 Fair

25-39 Poor

10-24 Very Poor

0-9 Failed

UTW Condition Survey


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Belvoir Ave - Chattanooga, TN

Green Street - Athens, TN

Highway 56 - McMinnville, TN

Concord Road - Knoxville, TN

Cusick Street (out), Maryville, TN

Cusick Street (in), Maryville, TN

Weigh Station (app.)- No. GA

Weigh Station (leave)- No. GA

Wesley Chapel - Dekalb Co., GAMarbut Rd. - Dekalb Co., GA

1993 76 76 77

1994 85 83 83

1993 91 86 79

1992 96 94 95

1993 93 89 87

1993 75 71 72

1993 97 97 97

1993 95 93 93

1993 85 82 901993 95 91 79

Project

Year

Const.PCI

1994

PCI

1995

PCI

1999


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One Final Note


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For concrete resurfacing, payment should be:

Cubic Yard Square Yard

NOTE: Divided payment is the most

equitable and economic.


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Any Questions ?

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