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1

Continuously Reinforced Concrete Pavements - CRCP

(Pavimentos de Hormigón con Reforzamiento Continuo)

Jeffery Roesler, Ph.D., P.E.Associate Professor

Department of Civil and Environmental EngineeringUniversity of Illinois Urbana-Champaign

Profesor VisitantePontificia Universidad Católica de Chile

Departamento de Ingeniería y Gestión de la Construcción4 Noviembre 2009

Acknowledgements

• Illinois Department of Transportation– Bureau of Materials and Physical Research

• Dr. Erwin Kohler– Ph.D. thesis (2005)

• University of Illinois– Matt Beyer, M.S.

• M-EPDG (2007)– Drs. Mike Darter and Lev Khazanovich

Presentation Overview

1. Introduction/Overview to CRCP

2. Illinois Experience

3. CRCP Distresses

4. Construction Process

5. CRCP Full-Scale Testing Results

6. Structural Design of CRCP

Continuously Reinforced Pavements• No man-made “joints”

• Steel reinforcement bars

• Numerous transverse cracks

History• First used in 1921

• Experimental sections in the 1940’s

• More than 28,000 miles in the USA

Why construct CRCP?

• Long-life pavement option

• Minimal maintenance

• Smooth ride

• High traffic volumes

What do we design for in CRCP?

1. Crack Spacing / Crack Width• geometry, materials, climate dependent

2. Repeated load resistance (fatigue)• Punchout development

2

CRCP Performance Characteristics

• 1 to 2 m crack spacing• Tight crack widths

– High load transfer efficiency

• Non-erodible support layers– No loss of support

• Low permanent deformation of support– Uniformity of support important

• Concrete durability– Many failures from non-structural deterioration

Overview of CRCP Early Behavior

• Basic analysis and stress diagrams

Transverse Cracks

• CRCP have transverse cracks to distribute movement

• Cracks are affected by– drying shrinkage

– temperature changes

– Slab-base friction

– degree of bonding between concrete and steel

– slab geometric and material properties

• Crack width (CW) performance:aggregate interlock load transfer efficiency

CRCP Failure

• Deterioration of transverse cracks

• Punchouts

CRCP CRACKING PATTERN

Continuous Steel

3

Illinois I-55 CRCP

CRCP Punchout Failure

x

y

CRCP Distress Development

Punchout• Longitudinal cracks propagate

• Structural failure

• Segment breaks and displace downwards

Mechanism of Punchout Development (M-EPDG)

Longitudinal crack initiation

Direction of Traffic

Pavement edge

Deteriorated transverse crack

Punchout


Pavement edge


Punchout

Loss of supportNarrow Crack spacing1

2

3

4

5

Tire footprint

Selezneva (2002)

LTE and other factors leading to CRCP failure

MECHANISTIC DESIGN CONSIDERATIONS FOR PUNCHOUT DISTRESS IN CONTINUOUSLY REINFORCED CONCRETE PAVEMENT(1990) Zollinger, DG; Barenberg, EJ.

• High rebar stress at crack

• Wide cracks→ spalling

• LTE

• Bending stress

4

History of CRCP in Illinois• US-40 near Vandalia 1947

– 18 & 20 cm CRCP with 0.3, 0.5, 0.7 and 1.0% steel

– Parts replaced as part of I-70

– Remainder performed for 50+ years

• 1960’s experimented with 15, 18, and 20 cm CRCP, base type, steel depth and percentage

• Originally adopted 18 cm and 0.6% steel as Interstate standard– Broken steel– Low cover depth steel = increased cracking– D-cracking problems

• Quickly adopted 20 cm CRC @ 0.7% steel as replacement for 25 cm, 100-foot jointed design

• Mid -1970’s traffic required 23 and 25 cm CRC• Current Maximum thickness 36 cm

– CRCP if design traffic is > 35 million ESAL’s(4,000 trucks 2-way with growth in 20 yrs)

History of CRCP in Illinois

Illinois

ClusterY-crackMeanderingDivided

Crack Spacing (ft)Average : 4.2Range: 1.6 - 10.1Std. Deviation: 2.7

Tayabji, S.D., Stephanos, P.J., Gagnon, J.S., Zollinger, D.G. Performance of Continuously Reinforced Concrete Pavements. Volume 2 - Field Investigations of CRC Pavements, Report FHWA-RD-94-179, 1998.

“D” CRACKED CONCRETE

“D” CRACKED PAVEMENT

I-39 CRCP Photo Review

CRCP 16 years old

“D”-Cracked Performance

5

D-cracking

6

Transverse Crack Spalling

- more of a problem in Texas

I-57 CRCP Effingham, IL

Longitudinal cracking

Longitudinal Crack in Core

Longitudinal Cracking of CRCP (I-39)

CRCP Tube Feeding

• Heavy bars (#7) sunk in concrete• #7 bar weighs 2 times #5 bar

Bar Corrosion

7

Extended Life CRCP in Illinois

• 30-40 Year design life

• ~500 million ESALs

• Tighter concrete specifications

Aggregate Working Platform

Long-Life CRCP Pavement Designs

10 to 15 cm

40 Year

CRC

Asphalt Concrete BaseAggregate Working Platform

30 cm

0.8% Steel Epoxy Coated

36 cm

CRCP Test Sections (UIUC)

• Sec.1 - 5: natural cracks, simulated wheel loads applied, and results reported in this study.

• Sec. 6 - 10: induced cracks, not loaded

Kohler and Roesler, Transportation Research Record 1900, pp 19-29, 2004

p=0.55%, #5h=254, d=89

p=0.80%, #6 p=1.09%, #7 p=0.80%, #6 p=0.80%, #6

p : percent of steel# : bar size (US system)h : concrete thickness (mm)

p=0.80%, #6 p=1.09%, #7 p=0.78%, #7 p=0.78%, #7

150 m

Lane 2

Lane 1

p=0.55%, #5

6 7 8 9 10

1 2 3 4 5

26 m

h=254, d=89 h=254, d=89 h=254, d=89 h=254, d=178

h=356, d=114h=254, d=89h=254, d=89h=254, d=89 h=356, d=89 & 178

d : depth of the steel layer (mm)

Section design & construction

• Concrete thickness was 10 or 14 in., on 4 in. asphalt base, and 6 in. granular subbase

• 26 longitudinal epoxy-coated steel bars, spaced 5.5”apart

• All transverse cracks developed naturally (Lane 1)

CRCP Cross-Section

•Base must be stabilized (4 to 6 in.)

•Subbase is granular material (12 to 24 in.)

CRCP Structural Test Sections

• Concrete thickness (10 & 14 in.)

• Steel Content (0.6, 0.8, & 1.1%)

• Depth to steel (3.5 & 4.5 in.)

• Crack spacing– natural vs. induced

• Steel Bar Size (#5, #6, #7)

• 2-layer vs. 1-layer Steel

8

Cross-section (single layer) Cross-section (single layer)

Cross-section (double layer) Two vs. One Layer Reinforcement• Texas DOT used for 15 years

– Should perform better?

• No performance information

• Cluster cracking (Zollinger 1999)– Result of curing and depth of steel

• Don’t coincide two layer of transverse reinforcement

• Longitudinal reinforcement on top of each other

Aggregate Subbase Compaction Final Asphalt Concrete Base Layer

9

5.5in. Plastic Chair CRCP Chairs (Steel)

Chair Set-up Steel Layout

Steel Ties Steel Tying

10

Bar Splices Single Layer Steel

Two-Layer Chairs Two-Layer Steel

Consolidation Below Steel? Final Steel Placement

11

Lug System (End Restraint) Fabricated Lug Cage

Construction Joint Lug System In-Situ

Lug Fastening CRC PavingPlacer / Spreader

12

Concrete Placement – Lane 2 Final CRCP Sections

36 cm CRCP Continuously Reinforced Concrete Pavement (CRCP) Sections

Transverse Crack Development

1.1%

0.8%

0.6%

0.8%

(10 in.)

(10 in.)

(10 in.)

(14 in.)

Crack Spacing (L) and Width (CW) Formulas

f

2

21)()( 0

1

2 L

h

zC

dc

PLU

E

cTzLCCzcw ii

bi

bm

icZciSHR

b

bm

PCC

dcPUF

hCf

Lt

1

0

2

2128

M-EPDG

13

Crack Spacing (Actual vs. Predicted)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Predicted mean crack spacing (m)

Act

ual m

ean

crac

k sp

acin

g (m

)

S1S4

S2

S3

Crack spacing (m) Section

Number of cracks Average Min Max STDV

S1 15 1.62 0.27 7.96 2.38 S2 27 0.93 0.27 2.68 0.60 S3 33 0.76 0.24 1.71 0.37 S4 15 1.62 0.21 4.69 1.48 S5 4 NAa 1.34 10.49 NAa

LTE of CracksLTE by Weight vs. StationLane 2, Induced Cracks

80%

82%

84%

86%

88%

90%

92%

94%

96%

98%

100%

0 50 100 150 200 250 300 350 400 450 500

Station

Lo

ad T

ran

sfer

Eff

icie

ncy

9000 lbs.

16000 lbs.

18 128 341Soff-Cut

Soff-Cut

Tape Tape

ATLAS CRCP Testing Loading

• Single aircraft tire

• 9 to 13 km/h, a bi-directional trafficking mode

• fixed lateral position along the edge of the pavement

• Load level from 45 to 245 kN (10 to 55 kips)

Rebound Vertical Deflection0.6% steel and 10 in. thickness

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 20 40 60 80 100 120

Passes (Thousand)

Reb

ound

Def

lect

ion

(mm

)

10 kips 30 kips 35 kips 50 kips

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 20 40 60 80 100 120

Passes (Thousand)

Reb

ound

Def

lect

ion

(mm

) 10 kips 30 kips 35 kips 50 kipsCrack 1

Crack 2

Rebound Vertical deflections14 in. with 0.8%

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 10 20 30 40 50 60 70

Passes (Thousand)

Reb

ound

Def

lect

ion

(mm

)

10 kips 35 kips 45 kips 55 kips

D-24.1D-28.8D-44.0D-63.1

• Increase during times of constant loading

45kN 156kN 200kN 245kN

14

Load transfer efficiency(Small crack width)

LTE 28.8

50

60

70

80

90

100

110

0 10 20 30 40 50 60 70

Passes (Thousands)

LTE

(%

)

10 kips

35 kips

45 kips

55 kips

50

60

70

80

90

100

110

0 25 50 75 100 125 150 175

Passes (Thousands)

LTE

(%

)

156 kN133 kN45 kN

Variation of LTE with Temp.

75

80

85

90

95

12 18 0 6 12 18 0 6 12 18 0 6 12 18 0 6 12

-6

-4

-2

0

2

4

6

8

10

12

mov.avg 17 passes

T diff

75

80

85

90

95

12 18 0 6 12 18 0 6 12 18 0 6 12 18 0 6 12

30

32

34

36

38

40

42

44

46

48

50

mov.avg 17 passes

Tavg

LTE

Time

Time

LTE

Investigation in punchout one Section 2 – Failure Pattern

Permanent deformation

• Estimated permanent deformation at two cracks in Section 2

Profile • Longitudinal profile at the edge as loading

progressed

• 20 mm peak permanent deformation

15

Profile Measurement for permanent deformation

-35

-30

-25

-20

-15

-10

-5

0

051015202530354045505560657075808590

Station (ft)

Ele

vatio

n (m

m)

20-Feb

7-Apr

6-Jun

13-Jun

18-Jun

19-Jun

End

Section 3

•10 in. slab, 1.09% steel

•Testing w/ tent

•Test started on June 1st

•33 transverse cracks

Cracking after loading Damaging loads

• Load history, total ESALs, and ESALs at failure for each section

0

50

100

150

200

250

- 25 50 75 100 125 150 175 200 225 250

Load

(kN

) Section 3Reps= 163,400ESALs= 627 MESALs f= 548 M

0

50

100

150

200

250

- 25 50 75 100 125 150 175 200 225 250Thousand Passes (Reps)

Load

(kN

) Section 4Reps= 64,300ESALs= 764 MESALs f= --

0

50

100

150

200

250

- 25 50 75 100 125 150 175 200 225 250

Load

(kN

)

Section 1Reps= 246,800ESALs=911 MESALs f=511 M

0

50

100

150

200

250

- 25 50 75 100 125 150 175 200 225 250Thoussand Passes (Reps)

Load

(kN

) Section 2Reps= 118,600ESALs= 778 MESALs f= 230 M

Section Failure Total ESALS

1 Yes 900

2 Yes 800

3 Yes 650

4 no 750

5 no 13

Summary of CRCP Section Failure

Section one

Section two

Section three

Section four

Section five

Duration of testing(1)12 months(6/16/02-6/23/03)

11 weeks (6/30/03-9/13/03)

10 weeks (5/26/04-8/4/04)

9 weeks (1/3/04-3/6/04)

2 weeks (4/6/04-4/15/04)

Total load repetitions 246,800 118,600 163,400 64,300 1,800

Total ESALs 911 M 778 M 627 M 764 M 12.5 M

Approx ESALs at first failure 511 M 230 M 548 M >764 M N/A

Maximum load applied 222 kN 222 kN 245 kN 245 kN 156 kN(3)

Pavement temperature range 1-27°C (2) 24-35°C 18-27°C -4-10°C 4-18°C

Failure description Extended punchouts

Extended punchouts

Extended punchouts

Section did not fail

Response loading only

34k

1i

i

i40

Pn18ESALs

÷

Full-Scale CRCP Testing Summary

Estimated ESALs at time of the first failure – 230 to 548 millions for the 10 in. sections

– no damage after 764 millions in the 14 in. section

Performance of the CRCP :– under small crack widths (less than 0.15 mm) LTE remains intact despite the heavy wheel loads

– punchout failure controlled by the underlying permanent deformation

16

Crack width & Crack movement

Existing CW data

• Measurement of CW– Crack comparators

– Microscope

– Dial gages, LVDTs

• CRCP CW data

– less than 0.2mm (IL)

– less than 0.5mm (TX)

– “about” 0.1mm (Japan)

• All at the surface

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1 10 20

Time in pavement life (years)

Cra

ck W

idth

(m

m)

0.0030.0050.0070.01

Steel content 7 in slabs

Horizontal crack movement

• Vertical load

• Slab bends with load near crack

• Bottom part opens up

• Upper part of the crack closes

Crack Width Profile

17

-0 .0 30

-0 .0 25

-0 .0 20

-0 .0 15

-0 .0 10

-0 .0 05

0 .0 00

0 .0 05

0 .0 10

0 10 20 30 40 50 6 0 7 0 8 0

S ta tio n (ft)

Cra

ck o

pen

ing

(mm

)

-Crac k a t s ta tion 24 .4 in s ec tion 1

-10 kips w hee l load-Sens or near top (1 inc h )

Crack face rotation

Closing movement

Load Spectra Tests

-0.070

-0.060

-0.050

-0.040

-0.030

-0.020

-0.010

0.000

0.010

0.020

0.030

0 100 200 300

Load(kN)

Clo

sing

Op

enin

g

Hor

izon

tal c

rack

mov

em

ent

(m

m)

c)

Crack Width

-30 -20 -10 0 10 20 30

Distance from crack (m)

Load=227kN

b)

-0.070

-0.060

-0.050

-0.040

-0.030

-0.020

-0.010

0.000

0.010

0.020

0.030

-30 -20 -10 0 10 20 30

Distance f rom crack (m)

Hor

izon

tal c

rack

mov

emen

t (m

m

Op

en

ing

Clo

sin

g

Load=40kN

a)

Crack Width (CW)

• Obtained from crack closing

• At the change in slope– Initially linear with load

– Closing+compression at crack face

Bi-linear behavior

CW = (Closing)L1

Horizontal movement vs load level

L1

Ope

ning

Load

Clo

sing

Compression

CW with ATLAS wheel load

CW Variability (Section 3)

• 31 cracks measured

0

20

40

60

80

100

120

0 5 10 15 20 25

Crack location (m)

Cra

ck w

idth

(m

icro

ns)

0

1

2

3

4

5

6

7

8

9

10 20 30 40 50 60 70 80 90 100

Crack Width Intervals (microns)

Num

ber

of C

rack

s

Factors affecting crack width

• Temperature:– Daily and seasonal variations– Max drop in temperature (crack formation)

• Drying shrinkage – Non-uniform in depth– Specially important at early age

• Subbase friction– Opposes movement

– Depends on subbase material

• Bond-slip– bond-slip zone near crack’s face– bond stress in the bond-slip zone is complex– Reinforcement steel (amount and depth)

CW = ·T · L (unrestrained)

Others:• Concrete aggregate type

• Moisture gradient

• Construction season

• Method of concrete curing

18

M-EPDG Crack Width model

• Crack Width model for CRCPMechanistic-Empirical Pavement Design Guide

Crack spacing

Drying shrinkage

Temperature drop

Restraints

iPCC

i

PCCiSHRi E

fcTLCCCW

i

2

fL

hC

dc

PULf

bi

m

2

210

1i

Base frictionCurling (thermal and moisture)Steel reinforcement

Findings of ATLAS CRCP Tests

Achieving tight crack width <<1mm– extends performance (<0.5mm)

• Avoid support layers with high permanent deformation potential

• Infinite fatigue life at 14in. and probably at 12 in.

Effect of Air Temperature on CRCP Failures

0%

5%

10%

15%

20%

25%

30%

35%

40%

50-60 60-70 70-80 80-90 90-100

Air temperature (°F)

Per

cen

tag

e of

Fai

lure

s

Schindler and McCullough (2002) – TxDOT study

10-15C 15-21C 21-27C 27-32C 32-38C

Construction Issues

• Concrete mix design – Concrete shrinkage

– Lower zero stress temperature!• Mix temperature (water, aggregates)

• Mix proportions (max. size aggregate)

• Curing– Minimize climatic effects

– Solar radiation, wind, evaporation

• Asphalt concrete base temperature

Zero-stress temperature

Estimate of Tzs: M-EPDG formula

95.5% of peak temperature

30

40

50

60

70

80

90

100

Pav

emen

t T

empe

ratu

re (

F)

-2

0

2

4

6

8

10

Diff

eren

ce T

op-B

otto

m (

F)

DG2002:“temperature at which the concrete hardens sufficiently to cause cracks to open when the concrete temperature drops below its value”

MMTHCCz

T

24001.1

8.110005.059328.0

Temperature after construction

Tdiff after construction(no built in curling)

Zero-stress temperature

Section 4-Cr.1

0.000

0.010

0.020

0.030

0.040

0.050

0.060

20 30 40 50 60

Temperature (F)

CW

(m

m)

At early age: zero-width = zero-stress (temperature)

Later in the life of the concrete:zero-width should > zero-stress (temperature)

But it was found to be lower crack width is not increasing with age

Total pavement length increases blowups

Crack closing temperature(zero-width temperature)

19

Zero Stress/ Zero Width Temperature

0

10

20

30

40

50

60

70

80

90

Section 1 Section 2 Section 3 Section 4 Section 5

Zer

o-st

ress

/ C

losi

ng t

empe

ratu

re (

F)

95.5% peak Crack closing Eq. 5.8

Section Cr.1 Cr.2 Cr.3 Cr.4 Section average Section 1 68.8 66.3 71.4 65.5 68.0 Section 3 75.7 73.8 71.0 72.1 73.1 Section 4 52.6 59.2 57.7 49.0 54.6 Section 5 66.4 - - - 66.4

Zero Width Temperature

Illinois DOT Extended-Life CRCP

• CRCP Specifications and guidelines for construction and materials

Aggregate Screening

ASTM 666 used since 1982. Freeze in air - thaw in water.

Test run to 350 cycles.

Average expansion of 3 test beams.

Decided to use standard test method. 20 year aggregate - Limit to 0.060% expansion.

Field performance correlated to test.

No overlay during 20 years of pavement life.

30 year aggregate - Limit to 0.040% expansion.

40 year aggregate - Limit to 0.025% expansion.

Cement and Fly Ash Requirements

30 Year pavement. Same as 20 year.

No additional restrictions.

40 Year pavement. Must address alkali’s - less than 0.60% in cement

and less than 1.5% in fly ash.

Options: Use a low alkali cement.

Test cement/fly ash/aggregate - must have expansion less than 0.10% under ASTM 1260 at 16 days.

Concern is in sands - source of silica.

Concrete Mixture Requirements

Same as current 20-year.

Water/cement ratio -

Beam Strength - 4.5 MPa (650 psi ) Center point loading.

14 Days.

Unchanged from 20 year pavement design.

Why increased strength is not used: More cement - possible additional reactivity problems.

More effective to add thickness to reduce stress.

Illinois CRCP Thickness Determination

• Currently using IL-Modified AASHTO• In use since 1970’s• Performance indicates design is

conservative• Research underway at University of Illinois

to update method– Will likely adopt some version of M-EPDG for

CRCP

20

5 Million ESAL’s

Soil CBR or “k”

Soil CBR = 3.0

“k” = 100

100 ft Jointed = 10in.

CRCP = 8in.

CRCP 80% of Jointed

Typical Illinois CRCP Thickness Design

Thickness ESAL, Millions

8 in. 5

10 in. 20

12 in. 100

14 in. (max) 300+

Actual vs. Design ESAL (no durability cracking)

0

5

10

15

20

25

30

35

40

Cum

ulat

ive

Million

ES

10-inJRCP

7-inCRCP

8-inCRCP

9-inCRCP

10-inCRCP

HMAC

50th Percentile ESAL, million Design ESALs, million

40-90 MESALs

Design ESALvaries

Darter et al. (1979)

Steel Requirements

• All epoxy coated ASTM A706.

• Percent CRC Steel

– Grade 60

– 0.70% (20-yr)

– 0.80% (30-yr)

– Maximum #7 bar

• Tie bars:

– Grades 40 or 60

– #6 x 24”• 24” centers if butt joint

• 30” centers if sawed joint

21

Constructing CRCP Pavement

• Paving Equipment:

– Max speed 3’ per minute unless plan in place

– Vibrator frequency monitoring required.

• Tining - randomly spacing (to reduce noise)

• Curing:

– Spray on curing compound.

– Period - 7 day minimum.

– No traffic of any kind allowed during curing.

• Smoothness Requirement:

– Zero blanking band.

– Incentive/disincentive

Constructing Support Layers

Embankment: AASHTO T99

Max. Moisture 110% of optimum. Min. 95% density in all of embankment.

Aggregate Subbase: 12 in. Crushed aggregate.

Stone. Gravel (crushed). Crushed concrete. Crushed asphalt concrete Well graded - Max 200 mm (8”)

Constructing Base Layer

Base: Bituminous - Superpave mixture

19.0 mm Binder Mix.

N 30.

Anti-strip added if needed.

Paving between May 15 and Oct. 15 - White-wash (lime water) bituminous base.

Water cool

reduce temperature and chance of flash setting from bottom up.

IDOT Reinforcing Bar Standards

50-Year California CRCP

Natural Crack shapes and patterns

• Non-uniform crack patterns are detrimental and common

• They lead to spalling and punchouts

• Out of 23 sections studied (*) :– 20 had cluster cracks, and some had them in several locations

– All had Y-cracks (2% to 23%)

– CRCP sections in IL, IA, OK, OR, PA, and WI

Cluster cracks

Y-cracks Meandering crack

Pavement Width

Divided cracks

(*) Tayabji et al. Performance of Continuously Reinforced Concrete Pavements. Volume 2 - Field Investigations

of CRC Pavements, Report FHWA-RD-94-179, 1998.

22

Active Crack Control

Saw-cut

Tape Insertion

Natural vs Induced Cracks

Cracks vs. Time

0

20

40

60

80

100

120

0 100 200 300 400 500

Time (Days After Pour)

Nu

mb

er

of

Cra

ck

s

Lane 1

Lane 2

Crack development

Lane 1

0 100 200 300 400 500Station (feet)

07/15/0303/11/03

12/10/0211/12/0210/10/02

09/10/0208/12/02

07/11/0205/13/0204/11/02

03/12/0202/12/0201/11/02

12/14/0112/10/01

Lane 2

0 100 200 300 400 500Station (feet)

07/15/0303/11/0312/10/0211/12/0210/10/0209/10/0208/12/0207/11/0205/13/0204/11/0203/12/0202/12/0201/11/0212/14/0112/12/0112/10/01

Natural cracks

• Crack location and time of crack surveys

• More cracks developed early in Lane 2

• Some natural cracks occurred in Lane 2 0

2

4

6

8

10

12

0 50 100 150 200 250 300 350 400 450 500

Station (feet)

Cra

ck s

paci

ng (

feet

)

Crack spacing 5-points moving average


0

2

4

6

8

10

12

0 50 100 150 200 250 300 350 400 450 500

Station (feet)

Cra

ck s

paci

ng (

feet

)

Crack spacing 5-points moving average Panels starting at passive cracks


Lane 2 – Active Crack

Lane 1 – Passive Crack

CRCP Crack Control

Continuously Reinforced Concrete Pavement DESIGN

DESIGN:

Longitudinal reinforcementRandom transverse cracksCracks kept tightSmooth pavement, long

life

PERFORMANCE:

Transverse cracking

Punchout development

CRCP Design Methods

• AASHTO (1986) Nomograph– Thickness same as JPCP

• M-EPDG (2007)– Different JPCP and CRCP methods

• Proposed Method Illinois DOT (2009)– Modified M-EPDG

23

AASHTO (1986)

• Crack width criteria

AASHTO (1986)

• Crack spacing criteria

AASHTO (1986)

• Steel stress criteria

AASHTO-86/93 Guide for Design of Pavement Structures

• 3 criteria– Crack Spacing

– Crack Width

– Steel Stress

M-EPDG CRCP DesignARA (2007)

Punchout: Structural Distress in CRCP

Transverse Crack Spacing

Punchout Area

Longitudinal crack @ 4ftTransverse

Crack

• Results in loss of ride quality

• Costly repairs

DIRECTION OF TRAFFIC

Pavement edge

24

Mechanism of Punchout Development

Longitudinal crack initiation


Pavement edge


Punchout


Pavement edge

Deteriorated

Punchout

Loss of support Narrow Crack spacing 1

2

3

4

5

Tire footprint

Design GuideDesign Guide

Mechanistic-Empirical Punchout Modeling Approach

CRCP Structural Response ModelBending Stress -ij

Shear Stress - τij

Punchout Prediction

ModelFD

PO

Fatigue Damage Prediction Model

(Miner’s Rule)

Input ParametersTraffic, environment, material, geometry

Transverse Cracking Model

FDn

Nij

ij

= ij

ijTransverse Crack LTE Deterioration

Model

Loss of Edge Support Model


CRCP Structural Response Model

Traf

fic la

ne (

12 fe

et)

Pass

ing

lane

(12

feet

)

2 feet

Critical analysis segment

Surrounding CRCP segments

Tire footprints

Transverse crack

Mesh2” x 4”

Mesh2” x 6”

Mesh2” x 2”

Longitudinal joint

Pavement edge

Detail A (next slide)

Mesh2” x 4”

Mesh2” x 6”

Mesh2” x 4”

Mesh2” x 6”

Mesh2” x 2”

Mesh2” x 4”

Mesh2” x 6”

Direction of traffic


CRCP Structural Response Model (continue)

Detail A

Unloaded plateelement

Loaded plateelement

Traffic load

Transverse crackShear spring element

Subgrade Spring element

Node

a a

b

bheff


Models Used to Characterize Properties of Finite Elements

• PCC Strength Gain Model

• Effective Slab Thickness Model

• Transverse Crack Width Model

• Crack Load Transfer Deterioration Model

• Loss of Slab Support Model

• Equivalent Temperature Differential Model

• Enhanced Integrated Climatic Model

Axle Loading Used in CRCP Response Model

Axle Name

Total Wheels

Wheel Spacing, inch

Axle Spacing, inch

S1 S2 S3 L1 L2Single 4 12 84 96 n/a n/aTandem 8 12 84 96 48 n/aTridem 12 12 84 96 48 96

S1

L1

L2S2 S3Direction of traffic

Tire footprint


25

CRCP Stress Distribution for Different Transverse Crack LTE

LTE = 95% LTE = 20%

150 psi 342 psiDirection of traffic


Design Parameters Over CRC Pavement Life

Time, years

Traffic

PCC Modulus

Granular Base Modulus

Each load application

Each load application

2 8640 2 8640

Subgrade Modulus

Transverse Crack Width

Transverse Crack LTE


CRCP Structural Design AlgorithmInputs (Structure, Traffic, Climate)

Selection of Trial Design

Structural Responses (, τ, LTE)

Performance Verification(Failure criteria = punchouts per mile)

Design Reliability

No

Feasible Design

Rev

ise

tria

l des

ign

Yes

Damage Accumulation with Time

Calibrated Punchout ModelDesign

Requirements Satisfied?


Crack LTE Deterioration Model (based on Zollinger et al.)

100

1

18.1/3) - 500()log(183.0214.0log1

111*100

1

Base

bici

iTOT

LTE

PJa

LTE

f

eis

c

bsJf

eis

c

bsJ

eeeeci egedeaeJLog )(

si = s0i - Si-1

7.310

361

0.068

7.310

11

0.005

698.1

67.5

PCC

ii

iref

ijji

j

PCC

i

i

PCC

ii

iref

ijji

j

PCC

i

i

h

cwifESR

n

hcw

s

h

cwifESR

n

hcw

s

Loss of Edge Support Model

EE = AGE *(-7.4 + 0.342P200 + 1.557BEROD + 0.234PRECIP)/12

EE = Erosion extent from pavement edge, inchAGE = Pavement age, monthP200 = Percent subgrade passing the No. 200 sieve, %.PRECIP = Mean annual precipitation, inch.BEROD = Base erodibility index:

1 for LCB; 2 for CTB with 5% cement; 3 for ATB and CTB with cement <5%; 4 for GB with 2.5 % cement; 5 for untreated GB.

Fatigue Damage Prediction Model

• Miner's hypothesis:

• Number of Allowable Loads:

DamageApplied loads (n ) f ALS

Allowable loads (N ) f MRij

ij ij PCC

= ij

( )

( , )

Log Nj = 2.0(MR/ij)1.22 – 1

Nj = Allowable number of load applications of j-th magnitudeMR = Concrete modulus of rupture (psi).

= Bending stress due to loads of j-th magnitude, psi.ij

26

Calibrated Punchout Prediction Model

Life

ici

i Db

aPO

1 1

POi = Number of punchouts per mile at the end of i-th monthly increment

Di = Accumulated damage at the end of the i-th increment

a = 216.842 (Calibration constant)

b = 33.1579 (Calibration constant)

c = -0.58947 (Calibration constant)

Average Crack LTE

0

25

50

75

100

LT

E,

%

Punchout

0

5

10

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Pavement age, years

Pu

nc

ho

ut

pe

r m

ile

Average Crack Width

0

10

20

30

Cra

ck

wid

th,

mil

Cumulative Truck Volume per Lane

02468

101214

Cu

mu

lati

ve

T

ruc

ks

, m

ln

Slab thickness 9.3 inch% Steel 0.6Base Type GBAvg. crack spacing 55 inchClimatic zone WFAADTT (base year) 1,100Avg. ESAL/truck 1.0Truck Growth 6.50%

Pennsylvania LTPP Section 42-5020

00 5 10 15 20 25

Age, years

PCC CTE Sensitivity for Mississippi LTPP Section 28-5006

1

2

3

4

5

6

7

8

9

10CTE =7 x 10-6 oF -1

CTE =5.5 x 10 -6 oF-1 (LTPP)

CTE =4 x 10-6 oF-1

LTPP Section 28-5006State MSSlab thickness 8.2 inch% Steel 0.59Base type CTBClimatic zone WNFADTT (base year) 500Avg. ESAL/truck 1.1Compound Growth 8.0%

Initial MEPDG v1.0 CRCP Analysis• Concrete Materials

– MOR = 585 psi at 28 days (3rd point bending)– Cement content: 550 lbs/cy (w/c=0.42)– CTE = 5.5 x 10-6 /F (absorbtivity=0.85)

• Reinforcement– 20-year: 0.7% steel, #6 bars– 30-year: 0.8% steel, #7 bars– steel depth:

• 3.5” for 10, 60 million ESALs• 4.5” for 230 million ESALs

• -10F Built-in Curl

Traffic Inputs

• Bolingbrook Data– vehicle class distribution

• M-EPDG Default Values– hourly adjustment

– axle load distribution

– # of axle types/truck class

• Tire pressure = 80 psi

Vehicle Class Bolingbrook (NB)

4 1.6%

5 4.6%

6 3.7%

7 0.0%

8 6.7%

9 79.0%

10 0.9%

11 3.5%

12 0.0%

13 0.0%

CRCP Traffic Assumptions

AADTT values for MEPDG v1.0

20-year design10 million ESALs = 1,657 AADTT60 million ESALs = 9,918 AADTT230 million ESAls = 38,021 AADTT

30-year design10 million ESALs = 1,105 AADTT60 million ESALs = 6,612 AADTT230 million ESAls = 25,347 AADTT

AADTT = Average Annual Daily Truck Traffic

27

Design Features

• PCC thickness is design variable

• BAM = 4 inch

• A-7-6 soil (E = 7,500 psi)

• Crack spacing = calculate

• Construction month = August

Failure Criteria

• Punchout = 10/mile @ 95% reliability

• IRI = ignore this failure criteria

Chicago (Midway) – AC [20 year]

0

2

4

6

8

10

12

14

16

10 60 230

ESALs (106)

Th

ickn

ess

(in

ch)

MEPDG v1.0

IDOT

Chicago (Midway) – Tied [20 year]

0

2

4

6

8

10

12

14

16

10 60 230

ESALs (106)

Th

ickn

ess

(in

ch

)MEPDG v1.0 - tied separateMEPDG v1.0 - tied monolithic

IDOT

Chicago (Midway) [20 year]

0

2

4

6

8

10

12

14

16

10 60 230

ESALs (106)

Th

ickn

ess

(in

ch

)

MEPDG v1.0 - AC

MEPDG v1.0 - tied separate

MEPDG v1.0 - tied monolithic

IDOT

Proposed CRCP Design MethodIllinois DOT (2009)

• Implement simplified version of M-EPDG method into spreadsheet

• Similar mechanistic principles

• Use ESALs

28

Proposed CRCP Inputs

• Pavement thickness

• Design life– percent steel, bar size, depth to steel

• Climatic data (seasonal)– temperature gradients through pavement, temperature at

steel depth, ambient temperature

• Shoulder type– tied PCC, asphalt, gravel

• Design ESALs

CRCP Inputs, con´t

• Concrete properties– modulus, COTE, strength, ultimate shrinkage,

cementitious content

• Base/subgrade properties– modulus, thickness, type, k-value unbonded case

• Construction season– spring, summer, fall, winter

• Fatigue equation– MEPDG, IDOT, ACPA

CRCP Design Process

1. Environmental Effects– Four cyclic seasons

• Frequency of temperature gradients through pavement– curling stress calculation

• Average pavement temperature at steel depth– crack spacing, crack width calculations

• Average ambient temperature– Tset calculation

CRCP Design ProcedureFrequency Analysis - Champaign 12" PCC (fall)

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

16.0%

18.0%

≤ -30 -30 to-27.5

-27.5to -25

-25 to-22.5

-22.5to -20

-20 to-17.5

-17.5to -15

-15 to-12.5

-12.5to -10

-10 to-7.5

-7.5to -5

-5 to-2.5

-2.5to 0

0 to2.5

2.5 to5

5 to7.5

7.5 to10

10 to12.5

12.5to 15

15 to17.5

17.5to 20

20 to22.5

22.5to 25

25 to27.5

27.5to 30

> 30

ΔT (°F)

% T

ime

at

ΔT

CRCP Design Process

1. Environmental Effects• Climatic data for Champaign, IL

– Pavement thickness = 8”, 10”, 12” 14”

2

TECCURL

LOADCURLTOT R R=1.0 for now

CRCP Design Procedure

2. Mean Crack Spacing

b

bm

PCCt

dcPUf

hd

Cf

L

1

028

2

21

MEPDG (2007)

29


3. Crack Width

10002

PCCsteelPCCshr E

fcTLCW

MEPDG (2007)


4. LTE across cracks– Dimensionless shear capacity

– Crack stiffness• Agg/kl

– Assume no shear capacity loss

1001

18.1/)log()(183.0214.0log1

10011*100

1BASE

cic

LTE

RJlaLTE

MEPDG (2007)


5. Traffic Stresses– STT, STB, SLB functions of LTEs, LTEc CS/RRS

– Cataloged ILLISLAB results

– Calculate stress due to traffic loading, σLOAD

2

1

STBSTT

SLB

STT

STB

SLB

12

CRCP Design Procedure5. Traffic Stresses

– STT, STB functions of LTEs, LTEc CS/RRS

– Calculate stress due to traffic loading, σLOAD

72 in.

72 in.

44 in.100 in.

STBSTT

iL

ISLAB2000 Model

48” 48” 48” 48” 48”

100”

44”

144”

144”

144”

sLTE

jLTE

cLTE

shoulder

passing lane

driving lane


6. Damage– Fatigue equations

• MEPDG: Log N = 2.0(MR/σTOT)1.22 – 1

• IDOT: Log N = 17.61 - 17.61(σTOT/MR)

– Damage equation

1 ii

iii D

N

nfD

30

Equivalent Damage Ratio (EDR)

3414.00933.0,98

3064.00965.0,9885

2688.01138.0,8560

2806.01424.0,60

,

iis

iis

iis

iis

iSTT

LLTEIF

LLTEIF

LLTEIF

LLTEIF

EDR

5533.02264.0, iiiSTB LEDR


7. Punchouts / mile

a, b, c = calibration constants of 0.02, 1.000x10-32, 13975

• 50 Punchout/mile saturation limit

m

iDi

iTOTcbaPO

1log ,

1

MEPDG CRCP Calibration

• 22 States w/ 4 climatic regions

• 58 CRCP sections– 10 sections from Illinois

– Vandalia (US40), I-80, I-94 Edens – Heavy traffic

MEPDG CRCP Sections

CRCP Calibration Sections

0

5

10

15

20

25

30

35

40

45

50

1E-09 1E-08 1E-07 1E-06 1E-05

Accumulated Damage

Pu

nc

ho

ut/

mile

I-80

I-94 (Edens)

Calibration Curve

ATREL

CRCP Calibration SectionsSection Age, yr Damage

Observed PO/mile

Predicted PO/mile

Error

I80_EB_137.65 9.04 1.44E-08 1.3 0.31 0.98I80_EB_137.65 17.04 3.01E-08 4.2 5.87 2.78I80_EB_137.65 19.04 3.48E-08 3.23 9.70 41.82I80_EB_137.65 21.04 3.98E-08 10.7 14.78 16.67I80_EB_143.79 17.04 3.01E-08 7.1 5.87 1.52I80_EB_143.79 19.04 3.48E-08 15.5 9.70 33.68I80_EB_151.12 10.04 1.62E-08 0.748 0.50 0.06I80_EB_152.33 18.04 3.24E-08 6.4 7.62 1.48I80_EB_152.33 20.04 3.72E-08 11.15 12.09 0.89I80_EB_152.33 27.04 5.71E-08 33.33 32.64 0.47I80_WB_137.65 9.04 1.44E-08 1.3 0.31 0.98I80_WB_137.65 17.04 3.01E-08 6.45 5.87 0.34I80_WB_137.65 19.04 3.48E-08 11.15 9.70 2.11I80_WB_137.65 21.04 3.98E-08 23.7 14.78 79.53I80_WB_137.65 26.04 5.39E-08 27 29.88 8.28I80_WB_143.79 17.04 3.01E-08 11.34 5.87 29.96I80_WB_143.79 26.04 5.39E-08 50.88 29.88 441.13I80_WB_148.39 9.04 1.44E-08 2.26 0.31 3.80I80_WB_152.33 18.04 3.24E-08 0 7.62 57.99I80_WB_152.33 20.04 3.72E-08 5.28 12.09 46.39I80_WB_152.33 22.04 4.24E-08 23.76 17.68 36.92I80_WB_152.33 27.04 5.71E-08 60 32.64 748.37

I94_edens_ 28.46 14.04 1.16E-08 0 0.13 0.02I94_edens_ 28.46 22.04 2.08E-08 1 1.40 0.16I94_edens_ 30.11 14.04 1.16E-08 0 0.13 0.02I94_edens_ 30.11 22.04 2.08E-08 1 1.40 0.16I94_edens_ 32.90 14.04 1.16E-08 0 0.13 0.02I94_edens_ 32.90 22.04 2.08E-08 1 1.40 0.16

MEPDG Function

0

5

10

15

20

25

30

35

40

45

50

1E-09 1E-08 1E-07 1E-06 1E-05

Accumulated Damage

Pu

nch

ou

ts/m

ile

I-80

I-94 (Edens)

Calibration Curve

ATREL

31

Design Charts30 year, Kd=50 psi/in, Reliability=95%

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

10 40 70 200

Design ESALs (millions)

Sla

b T

hic

knes

s (i

nch

es)

Tied PCC (monolithic) Tied PCC (separate) Asphalt/Granular


8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

10 40 70 200


Sla

b T

hic

knes

s (i

nch

es)



8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

10 40 70 200


Sla

b T

hic

knes

s (i

nch

es)


Slab Thickness (in)Design Comparisons

k-value(psi/in.)


10 40 70 100

IDOT M-E IDOT M-E IDOT M-E IDOT M-E

50 9.5 10.5 11.0 11.0 12.0 11.5 13.5 12.5

100 9.0 10.0 11.0 10.5 12.0 11.0 13.5 12.0

200 9.0 9.5 11.0 10.0 12.0 10.5 13.5 11.5

*Both design procedures assume 20 year designs and tied concrete shoulders*M-E design procedure assumes 95 percent reliability

Summary of New Features

• Proposed CRCP Design Process– Crack spacing prediction

– Fatigue-based thickness design

• New Equivalent damage ratios

• Top of slab strength reduction factor

CRCP Program Limitations

• Erosion analysis

• Reliability is a Traffic Multiplier of 4

• Load and temperature stress superposition

– R=1.0

• Widen Lane stresses - none

• Tied shoulder*

LOADCURLTOT R

32

Limitations, con’t

• Verification for high ESAL count– >100 million

• Calculated stresses are extremely low– Is this the right approach or are we using the

wrong thickness?

• CRCP = 0.8*JRCP– No guarantee that CRCP will be thinner

Acknowledgements

The Illinois Center for Transportation (ICT) is

an innovative partnership between the Illinois

Department of Transportation (IDOT) and the

University of Illinois at Urbana-Champaign

(UIUC).

Questions?

[email protected] or 217-265-0218

CRCP Projects Reports• Beyer, M. and Roesler, J.R., Mechanistic-Empirical Design Concepts for Continuously

Reinforced Concrete Pavements in Illinois, Final Report, FHWA-ICT-08-040, Illinois Center for Transportation, University of Illinois, Urbana, IL, April 2009, 85 pp.

• Kohler, E. and Roesler, J. (2006), Accelerated Pavement Testing of Extended Life Continuously Reinforced Concrete Pavement Sections, Final Report, Transportation Engineering Series No. 141, Illinois Cooperative Highway and Transportation Series No. 289, University of Illinois, Urbana, IL, 354 pp.

• Kohler, E., Long, G., and Roesler, J., “Construction of Extended Life Continuously Reinforced Concrete Pavement at ATREL,” Transportation Engineering Series No. 126, Illinois Cooperative Highway and Transportation Series No. 282, UILU-ENG-2002-2009, University of Illinois, Urbana, IL, December 2002, 54 pp.

http://www.crcpavement.com/

Projects Publications• Kohler, E.R. and Roesler, J.R. ( 2006), “Crack Spacing and Crack Width Investigation

from Experimental CRCP Sections,” International Journal of Pavement Engineering, Vol . 7, No. 4, pp. 331-340.

• Kohler, E.R. and Roesler, J.R., (2006), “Non-destructive Testing for Crack Width and Variability on Continuously Reinforced Concrete Pavements,” Transportation Research Record 1974, Journal of Transportation Research Board, pp. 89-96.

• Kohler, E.R. and Roesler, J.R. (2005), “Crack Width Measurements in Continuously Reinforced Concrete Pavements,” ASCE Journal of Transportation Engineering, Vol. 131, No. 9, pp. 645-652.

• Kohler, E.R. and Roesler, J.R. (2004), “Active Crack Control for Continuously Reinforced Concrete Pavements,” Transportation Research Record 1900, Journal of Transportation Research Board, National Research Council, Washington, D.C, pp. 19-29.

• Kohler, E. and Roesler, J.R. (2005), “Repeated Load Behavior of Continuously Reinforced Concrete Pavement,” 8th International Conference on Concrete Pavement, August 13-18, 2005, Colorado Springs, CO, 17 pp.

• Kohler, E. and Roesler, J. “Avances en la investigación de pavimentos CRCP,” XV Simposio Colombiano Sobre Ingenieria de Pavimentos - 2005, Bogota, Colombia, March 9-13, 12 pp.

• Kohler, E.R. and Roesler, J.R. (2004), “Crack Width Determination for Continuously Reinforced Concrete Pavements,” Second International Conference on Accelerated Pavement Testing, September 25-29, 2004, Minneapolis, Minnesota, 19 pp.

Predicted Crack Width

0

2

4

6

8

10

12

14

16

18

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44

Pavement age, years

Cra

ck W

idth

, m

il

33

Crack Shear Capacity

icw

PCCiehs 032.0

005.0

Transverse Crack Shear Stiffness(Aggregate Interlock)

f

eis

c

bsJf

eis

c

bsJ

eeee

icegedeaeJLog )(

Transverse Crack LTE

LTEc i =

18.1

)log(183.0214.0

log1

100

1ic

i

Ja

Shear Transfer Deterioration of Cracks

PCC

i

h

cw

is

If < 3.8 iiref

ijji

j

PCC

i

i ESRn

h

cws

67.5 10

11

0.005 (55a)

otherwise iiref

ijji

j

PCC

i

i ESRn

hcw

s

698.1 10

361

0.068004.0 (55b)

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