urban arterial rural primary/interstate · 2018. 10. 8. · concrete overlays (1901 ... over poor...

CONCRETE OVERLAY

PERFORMANCE

Urban arterial Rural primary/interstate

Urban freeway/interstateIntersections Rural secondary roads

Questions

• Why Concrete Overlays?

• What types?

• How much $?

• How do they perform?

Benefits of Concrete Overlays

• Cost-effective

• Extends pavement life

• Easy to maintain

1978 Grundy Co. T-55 6” Overlay (PCI = 78, IRI = 122)

Reference Documents

2014 2015

Concrete Overlays (1901 – 2012)

• 1,152 concrete overlays nationwide

• 46 states

NCHRP Syntheses 99 & 204 (1982, 1994) & ACPA National Concrete Overlay Explorer (2013a)

ACPA

National Concrete Overlay Explorer

acpa.org

ACPA

National Concrete Overlay Explorer

Iowa Concrete Overlays

Over 2,000 miles & over 400 projects

(1960 - 2015)

Bonded vs. Unbonded

Bonded Overlays (2” – 6”)

• Add structural capacity

• Fair to Good condition

• Eliminate surface distress

• One monolithic unit

Unbonded Overlays (4” – 11”)

• Restore structural capacity

• Deteriorated condition

• Eliminate surface distress

• Minor or Major rehabilitation

The When is Important…

Maintenance

Resurfacing

Reconstruction

Evaluation Steps

1. Pavement History ( Records)

2. Field Review of Distresses

3. Coring Pavement

4. Additional Field Tests

(when necessary)

5. Condition Assessment Profile

BONDED OVER ASPHALT/COMPOSITE

KEYS TO SUCCESS

• Bonding is critical

• Small square panels reduce curling,

warping, & shear stresses in bond

(spacing in feet=1.5 x thickness in inches)

• Mill to remove surface distresses, or

improve bonding

• Leave 3” to 4” of HMA after milling

• Existing asphalt pavement < 120ºF

• Application of curing compound is critical

How Do Bonded Overlays over

Asphalt Work?

• Concrete bonds to the asphalt- Lowers the neutral axis- Decreases stresses in the

concrete

• Short joint spacing- Act like paver-blocks- Requires additional saws

• Fibers improve concrete toughness

BONDED OVERLAY ON CONCRETE:

KEYS TO SUCCESS

• Thickness 2” – 5”

• Match joints

• Existing joints - fair condition or be repaired

• Trans. joints full depth +1/2” Long. Joints at T/2

• Curing should be timely and adequate

• Coefficient of Thermal Expansion (CTE)

Coefficient of Thermal Expansion (CTE)

• Overlay CTE should be similar to underlying pavement

• If not, overlay CTE should be lower than exist. pavement

• Key ☞ similar coarse aggregate type

Shear ShearOverlay

Existing Pavement

Tensile stress

Joint Design– Full Depth Cut & Width

of Cut

UNBONDED OVER ASPHALT/COMPOSITE

PAVEMENTS: KEYS TO SUCCESS

• Thickness 2” – 6”

• Milling to eliminate 2”+ surface

distortions

• Existing asphalt pavement < 120ºF

• Partial bonding is acceptable

UNBONDED OVER CONCRETE

PAVEMENTS: KEYS TO SUCCESS

•Separator layer (1” asphalt or geotextile fabric)

•Faulting of 3/8 in. or less in the existing concrete

pavement

•Shorter joint spacing minimizes curling & warping

stresses

•No need to match joints

UNBONDED OVERLAYS CAN BE PLACED

OVER POOR CONCRETE PAVEMENTS

2007

D35-Kansas City Metro 9000 ADT

5” Unbonded Overlay

Excellent Condition

Unbonded Overlays - Separation

Geotextiles

• Nonwoven fabrics

• Daylight to foreslopes

• Tie into underdrain

system

Overlay Cost Survey

• 31 projects in 7 states in 2015

• Concrete furnish, placement (finishing, jointing, curing, etc.)

• Pre-overlay repairs, separation layer (if used) not included

$0.00

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

$4.50

Iowa Michigan Missouri Oklahoma South Dakota Minnesota Illinois

$2.52

$2.82

$3.35 $3.35$3.58

$4.07

$4.45

Average Concrete Overlay Cost ($/SY/in.)Bonded and Unbonded Overlays

$2.52

$4.07

$3.58$3.35

$2.82

$3.35

$4.45

Concrete Overlay Design

• BCOA (ACPA 2012) http://apps.acpa.org/applibrary/BCOA/

• StreetPave (ACPA 2014)http://www.acpa.org/streetpave/

• BCOA-ME

(Vandenbossche 2013)

http://www.engineering.pitt.edu/Vandenbossche/BCOA-ME/

BCOA-ME

Macro-Fibers

IHRB TR-698 - CONCRETE OVERLAY

PERFORMANCE ON IOWA’S ROADWAYS

• How to measure performance?

• ICPA history (Dan King)

• InTrans performance data

(Dr. Smadi & Inya Nlenanya)

• Data Analysis

(Dr. Ceylan & Yu-an Chen)

PERFORMANCE

25

BCOC 4%

UBCOC34%

BCOA45%

UBCOA17%

Percent of Data (based on length)

PCI Good to Excellent = 86%IRI Below 170 in./mi. = 92%




TR-698 SUMMARY

Whitetopping

NOTE: BCOA 6” AND UNDER CONSIDERED IN BONDED CATEGORY

PCI (%)

Concrete

overlay:

Percent of

data based on

number of

projects (%)

BCOC:

Percent of

data based

on number of

projects (%)

UBCOC:

Percent of data

based on

number of

projects (%)

BCOA:

Percent of

data based

on number of

projects (%)

UBCOA:

Percent of

data based

on number

of projects

(%)

100-81

(Excellent)55 21 46 60 66

80-61 (Good) 31 47 39 26 29

60-41 (Fair) 8 26 7 9 4

40-21 (Poor) 5 6 7 5 1

20-0 (Very poor) 1 0 1 0 0

Total 100 100 100 100 100

26

Total number of data points: 1,249Total number of projects: 387

PCI DISTRIBUTION

27

IRI (in/mile)

Concrete

overlay:

Percent of

data based on

number of

projects (%)

BCOC:

Percent of

data based on

number of

projects (%)

UBCOC:

Percent of

data based on

number of

projects (%)

BCOA:

Percent of

data based on

number of

projects (%)

UBCOA:

Percent of

data based on

number of

projects (%)

< 95 (Good)

40 54 33 42 43

96-169(Average)

51 38 56 50 45

> 170 (Poor)

9 8 11 8 11

Total 100 100 100 100 100

Total number of data points: 1,249Total number of projects: 387

IRI DISTRIBUTION

28

ADT (count) Percent of data basedon number of projects

(%)

<500 32

501–1,000 34

1,001–1,500 16

1,501–2,000 5

2,001–3,000 5

3,001–4,000 2

4,001–10,000 4

> 10,000 2

Total 100

ADT DISTRIBUTION

29

Total number of data points: 1,249Total number of

projects: 387

Excellent

Fair

Poor

Very Poor

Good

PCI vs AGE ENTIRE DATABASE

30

Total number of data points: 1,249Total number of

projects: 387

170 in./mi

IRI vs AGE ENTIRE DATABASE

22

67.461.2 64.4 63.5

74.679.8 83.0

78.474.2

0

10

20

30

40

50

60

70

80

90

100

1960-1969 1970-1980 1981-1985 1986-1990 1991-1995 1996-2000 2001-2005 2006-2010 2011-2015 TOTAL

Average PCI by Age of Overlay

220.0

136.5147.0

136.6 140.2127.0

112.093.0

110.0 118.0

0.0

50.0

100.0

150.0

200.0

250.0

1960-1969 1970-1980 1981-1985 1986-1990 1991-1995 1996-2000 2001-2005 2006-2010 2011-2015 TOTAL

Average IRI by Age of Overlay

6” Concrete Overlay on asphalt

490 ADT

20’ transverse joint spacing

PCI = 72, IRI = 115

1977 Boone R-18

1977 Washington County W-55

6” Concrete Overlay on asphalt

1360 ADT

15’ transverse joint spacing

PCI = 78, IRI = 122

34

• Analytical Investigation &

Field Investigation Plans

• Field Investigation

• Develop Phase II Research Plan

• Phase I Final Report

WHAT’S NEXT: OVERLAY JOINT

SPACING

Questions

www.cptechcenter.org