the mechanisms of healing of asphalt pavement by dingxin cheng for dr. lytton’s micromechanics...

The Mechanisms of Healing of Asphalt Pavement

By DingXin Cheng

For Dr. Lytton’s

Micromechanics Class

November 11, 2002

2

Outline

• Surface Free Energy Concept

• Fatigue and Healing Analysis

• Mechanical Testing Results

• Healing Mechanisms

3

Surface Free Energy

ABLW

2AB

Measurement of Asphalt-Wilhelmy Plate

Measurement of Aggregate

– Universal Sorption Device (USD)

6

lab

field

shiftfactor

K2f

K2I

Log Nf

Log

C

ALC

ULA

TE

D S

TR

AIN

Fatigue shift factor

7

Fatigue and Healing Model -(1)

• Fatigue model without rest period

nvJAdN

dc][ 0

)(,,,,,, 1 tWEmDfnA Rff

Where,

8

Fatigue and Healing Model -(2)

• Fatigue model considering the healing effect

dN

dhJA

dN

dc nv ][ 0

hThhhf ,,,

dN

dh2

.

1

.

9

Healing Curve

Rest Period

Hea

ling

Ind

ex

1

h2

h

1

h

2

h

10

R2 = 0.7797

4

6

8

10

12

14

16

1.5 1.7 1.9 2.1 2.3 2.5

Short Term Healing Rate

LW

Com

pone

ntShort-Term Healing Rate vs.

Non-Polar Component

11

R2 = 0.7445

0

1

2

3

4

5

6

0.2 0.3 0.4 0.5 0.6 0.7

Long-Term Healing Rate

Aci

d-B

ase

Com

pone

ntLong-Term Healing Rate vs

Polar Component

12

Summary of Effect of Surface Free Energy on Fracture Fatigue Healing

• Healing potential is promoted with

• Reduced LW

• Increased AB

LW and Healing Potential

0.005.00

10.0015.0020.00

Lif

shit

z-va

n d

er W

aals

com

po

nen

ts,

erg

s/cm

2

AB and Healing Potential

0.00

2.00

4.00

6.00

8.00

Aci

d-B

ase

com

po

nen

ts,

erg

s/cm

2

15

Testing Results and Healing Analysis- Aging Effect

0.002.004.006.008.0010.00

surf

ace

free

ene

rgy,

er

gs/c

m2

LW

AB

16

Asphalt Binder Fatigue Testing including Healing Effects

0

20

40

60

80

AAD-1 AAM-1 HCR

Asphalt Binder

Ave

rag

e p

erce

nt,

%

HPI (Healing Potential Index)

FLI (Fatigue Life Increase)

17

DMA Fatigue Data for AAM-1

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 2000 4000 6000 8000 10000

No. of loading cycles

No

rmal

ized

G*

without RP

with RP

Nf

18

DMA Data Fatigue for AAD-1

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5000 10000 15000 20000

No. of loading cycles

No

rmal

ized

G*

with RP

without RP

Nf

19

Asphalt Mixture Healing Testing -by Si, et al.

0102030

405060

Different Mix Type

Ex

ten

sio

n In

de

x, %

20

Result Comparison Table

Healing Potential Level

AAD-1 AAM-1 HCR

Surface Energy

Low Median High

Binder Fatigue Test

Low Median High

Mixture Fatigue Test

Low Median High

21

Mechanisms of Healing

22

Acid-Base Components of Surface Energy

2

221

r

ezzFatt

- Acid-Base Intermolecular Force

23

Acid-Base Attracting Energy Potential

• Two Particles

r

ezzdr

r

ezzU

r

att

221

2

221

24

Attracting Energy Potential of One Mole Material

r

ezzANU att

221

25

Repulsion Due to Electron Orbital Overlap

91

r

NBU rep

26

Net Acid-Base Attraction Energy

9

221

r

NB

r

ezzANUUU repattAB

27

Potential Energy of Acid-Base Interaction Versus Inter-particle Distances

-10

-5

0

5

10

15

0 1 2 3 4

Distance, r

Po

ten

tial

En

erg

y, U

U-attraction

U-repulsion

U-Acid-Base

Umin

r0

28

Lifshitz-van der Waals Components

• London Dispersion Force

• Debye Induction Force

• Keesom Orientation Force

621

r

RUdispersion

621

r

QU indi

6

22

21 )(

r

PNU didi

29

Net Lifshitz-van der Waals Potential Energy

92

6

22

21

621

621 )(

r

NB

r

PN

r

Q

r

RU LW

30

Potential Energy of Lifshitz-van der Waals Interaction Versus Inter-particle Distances

-10

-5

0

5

10

15

0 0.5 1 1.5 2 2.5 3 3.5

Distance, r

Po

ten

tia

l En

erg

y, U

U-attraction

U-repulsion

U-LW

31

Comparison of AB and LW Potential Energy

Changing with Inter-particle Distances

-8

-6

-4

-2

0

2

4

6

8

10

0 0.5 1 1.5 2 2.5 3 3.5

distance, r

Po

ten

tia

l en

erg

y, U

U - Lifshitz-van derWaalsU - Acid-Base

32

Healing Mechanism

Microcracking

Van der Waals

Acid-Base Forces

33