daba s. gedafa, ph.d., p.e. university of north dakota · falling weight deflectometer (fwd) is the...

Daba S. Gedafa, Ph.D., P.E.University of North Dakota

Perpetual pavements limit strains at the bottom of the asphalt concrete layer

Surface deflection testing is widely used for pavement structural evaluation

Deflection testing at the network level can: identify the beginning and end of management sectionsgroup pavement sections with similar structural capacities

to make “families”

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Falling weight deflectometer (FWD) is the most popular device for project-level deflection testing

Network-level FWD testing is unsafe, time consuming, and expensive

Rolling wheel deflectometer (RWD) measures surface deflections at highway speed

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RWDARA RWD and Close-up of Laser D

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Spatially Coincident Profiles

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Compare FWD and RWD center deflections and corresponding effective structural numbers (SNeff)

Establish the relationship between FWD and RWD center deflections and corresponding SNeff

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Section 1 2 3 4

Acronym KAPA

(Standard)

KAPA

(High Reliability)

KAPA 2

(Modified)KDOT

Surface Course 40 mm, SM 9.5 A (PG70-28)

Binder Course 60 mm, SM 19 A (PG70-28)

Base Course225 mm, SM

19A (PG70-22)

187.5 mm, SM 19

A (PG64-22)

225 mm, SM 19

A (PG64-22)

300 mm, SM 19A

(PG64-22)

Stabilized

Subgrade150 mm, 6% hydrated lime mixed with natural soil

Natural

SubgradeHigh plasticity clay (A-7-6)

Deflection:FWDRWD

Pavement temperature

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Pavement temperature

Deflection correction

Pavement structural capacity

Significant difference test

Linear regression

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0

5

10

15

20

25

30

35

40

45

Wat

son

Lela

nd

BELL

S3

Mea

sure

d

Wat

son

Lela

nd

BELL

S3

Mea

sure

d

Wat

son

Lela

nd

BELL

S3

Mea

sure

d

Wat

son

Lela

nd

BELL

S3

Mea

sure

d

S1 S2 S3 S4

Ave

rage

Pav

emen

t Tem

pera

ture

(o C)

Section and Method

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0.00

0.05

0.10

0.15

0.20

0.25

0.30

Avg Min Max Avg Min Max Avg Min Max Avg Min Max

S1 S2 S3 S4

Cen

ter

Def

lect

ion

(mm

)

Section

FWD RWD

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0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

Avg Min Max Avg Min Max Avg Min Max Avg Min Max

S1 S2 S3 S4

SNef

f

Section

FWD RWD

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y = 0.8478x + 0.039R² = 0.5462

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.14 0.16 0.18 0.20 0.22 0.24 0.26 0.28

RW

D C

ente

r D

efle

ctio

n (m

m)

FWD Center Deflection (mm)

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y = 0.1905x + 3.7392R² = 0.0315

4.0

4.2

4.4

4.6

4.8

5.0

5.2

5.4

4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4

RW

D S

Nef

f

FWD SNeff

BELLS3 equation gives a mid-depth pavement temperature close to the measured value

No significant differences between center deflections and corresponding effective structural numbers from RWD and FWD deflection data

There is:a linear relationship between FWD and RWD center

deflectionsno linear relationship between FWD and RWD SNeff

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Federal Highway Administration

Kansas Department of Transportation (KDOT)

Applied Research Associates (ARA)

Mustaque Hossain, Ph.D., P.E., KSU

Richard Miller, P.E., KDOT

Douglas Steele, P.E., ARA

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Contact:Daba S. Gedafa, Ph.D., P.E.University of North Dakota

E-mail: daba.gedafa@engr.und.eduOffice Phone: 701-777-3976

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