A reflexão de fendas na reabilitação de pavimentos rodoviários

Jorge Pais

Example of cracking reflection

Asphalt overlay over a

rigid pavement

Cracks in the asphalt

layer appear just above

the existing cracks of

the PCC

Examples of cracking reflection

Cracking reflection

in flexible

pavements

Cracks of the old

pavement

propagate to the

new pavement

layer

Example of cracking reflection

Reflective Cracking references

Cracks - nature and origin of cracks

Reflective cracking potential

Using FWD – Difference between vertical movements of the crack edges

Reflective cracking potential

Using CAM – Crack Activity Meter

Soluctions to reduce the reflective cracking

Increase the thickness of the overlay layer

thickness obtained by mechanistic-empirical pavement design

depending on the reflective cracking potential of the overlay

Use of an overlay system

grids

geotextiles

SAMI

steel reinforcement net

Use of asphalt mixtures with high reflective cracking resistance

lab testing to evaluate mixtures properties

models to estimate overlay life

Overlay system

Components of the overlay system

Interlayer products

Grids

Interlayer products

Application of grids

Example of problems with grids

Bonding problems

Interlayer products

Steel reinforcement net

Interlayer products

Steel reinforcement net

SAMI

SAMI application

SAMI application

Binder rate

Conventional binder: 1.3 – 1.7 l/m2 = 1300 – 1700 g/m2

Asphalt rubber: 2.4 – 2.7 l/m2 = 2400 – 2700 g/m2

Conventional asphalt mixture Asphalt rubber mixture

125 kg binder/m3 200 kg binder/m3

1250 g binder/cm/m2 2000 g binder/cm/m2

SAMI

Conventional binder: 1300 – 1700 g/m2 = 1.0 – 1.5 cm conv. asphalt mixture

Asphalt rubber: 2400 – 2700 g/m2 = 1.9 – 2.1 cm of conv. asphalt mixture

1.2 – 1.4 cm of asphalt rubber mixture

Secret?

Soluctions to reduce the reflective cracking

Increase the thickness of the overlay layer

thickness obtained by mechanistic pavement design

depending on the reflective cracking potential the overlay

Use of an overlay system

grids

geotextiles

SAMI

steel reinforcement net

Use of asphalt mixtures with high reflective cracking resistance

lab testing to evaluate mix properties

models to estimate overlay life

Models to consider the crack reflection

Empirical models

Extended multi-layer linear elastic models

Equilibrium equations based models

Finite elements plus traditional fatigue equation models

Finite elements plus fracture mechanics models

Crack band theory based models

Cohesive zone cracking models

Non-local continuum damage mechanics based models

Source: NCHRP 669

Testing apparatus used in reflective cracking

Evaluation of cracking reflection

Experience of the University of Minho

Use of Crack Activity Meter to measure the crack movements

Calibrate finite elements models to predict the

crack activity before overlay

Use of finite elements to predict the crack activity after

overlay

Apply the crack activity after overlay in the RCD to

predict the reflective cracking fatigue life

Crack Activity Measurements

Longitudinal crack Transverse crack

Crack Activity Measurements

Model for Crack Activity BEFORE Overlay

Useful to verify if crack is active

Crack Activity Measurements using FWD

Crack Activity Measurements

Crack Activity AFTER Overlay

Testing apparatus of the UMinho

Reflective Cracking Device

Cracked

pavement Crack

Overlay layer

Cracked

pavement

Specimen

Traffic load

Vertical actuator

Horizontal actuator

specimen

Reflective Cracking Device

Loading

Testing results

Testing results

Testing results

Crack opening during RCD testing

Crack opening (mm)

Load

Cyc

les

Prediction of overlay life

Wheel tracking tests

Wheel tracking tests

Numerical modeling of the test

Wheel tracking tests

Model to predict state of strain in the specimen

𝑬𝒗𝒎 = 𝒂 × 𝑬𝒐𝒗𝒆𝒓𝒍𝒂𝒚𝒃 ×𝑯𝒔𝒕𝒆𝒆𝒍

𝒄 ×𝑯𝑹𝒖𝒃𝒃𝒆𝒓𝒅

Evm: Von Mises strain Eoverlay: Stiffness of the overlay (MPa) Hsteel: Thickness of steel plates (mm) Hrubber: Thickness of the rubber (mm)

a b c d

2.651 0.9516 0.04264 0.1584

Ev

m m

od

el

Evm pavement

Most used cracking propagation model: Paris law

Stress Intensity Factor

Fracture tests

Disk-shaped Semi-circular bending

Direct

Tension Notched

bending

beam

Fracture tests

Disk-shaped test

Fracture tests

Notched bending beam

Fracture tests

Semi-circular bending

Fracture tests

Direct tension

Fracture tests

Disk-shaped results: Fracture energy

0

0,5

1

1,5

2

2,5

3

0 200 400

CM

OD

(m

m)

Time (seconds)

0

100

200

300

400

500

600

0 5 10 15 20

Load

(N

)

CMODfit (mm)

AC14

AC16

AC20

0

100

200

300

400

500

600

0 5 10 15 20

Load

(N

)

CMODfit (mm)

B6.0F1.5

B6.5F1.5

B7.0F1.5

Fracture tests

Disk-shaped

y = -0,05x + 60,18 R² = 0,97

0

10

20

30

40

50

60

0 500 1000 1500

Cra

ck le

ngt

h (

mm

)

Load (N)

0

500

1000

1500

2000

2500

0 2 4 6 8

Load

(N

)

CMODfit(mm)

AC14AC16AC20

Fracture tests

Notched bending beam

0

100

200

300

400

500

0 2 4 6

Load

(N

)

CMODfit (mm)

B6.0F1.5

B6.5F1.5

B7.0F1.5

y = -0,06x + 24,07 R² = 0,96

0

5

10

15

20

0 100 200 300 400

Cra

ck le

ngt

h (

mm

)

Load (N)

Fracture tests

Semi-circular bending: Cracking propagation

y = -0,20x + 97,48 R² = 0,96

0

10

20

30

40

50

60

200 300 400 500

Cra

ck le

ngt

h (

mm

)

Load (N)

Fracture tests

Direct traction

Conventional mixture Mixtures with fibers

0

500

1000

1500

2000

2500

0 0,5 1 1,5 2 2,5

Load

(N

)

CMODfit (mm))

0

400

800

1200

1600

0 0,5 1 1,5 2

Load

(N

)

CMODfit (mm))

Numerical modeling of fracture tests

Finite element model for disk-shaped

Numerical modeling of fracture tests

Numerical modeling of fracture tests

Load – CMOD (model vs lab)

Numerical modeling of fracture tests

Load – CMOD (model vs lab)

Temperature variation

Temperature at the pavement surface

-10

0

10

20

30

40

50

60

Jan-

04

Feb-0

4

Mar

-04

Apr

-04

May

-04

Jun-

04

Jul-0

4

Aug

-04

Sep

-04

Oct-0

4

Nov

-04

Dec

-04

Month

Pa

ve

me

nt

tem

pe

ratu

re

(ºC

)

pavement surface

Temperature variation

Temperature at the bottom of overlay

-10

0

10

20

30

40

50

60

Jan-

04

Feb-0

4

Mar

-04

Apr-0

4

May

-04

Jun-

04

Jul-0

4

Aug-0

4

Sep-0

4

Oct

-04

Nov

-04

Dec

-04

Month

Pa

ve

me

nt

tem

pe

ratu

re

(ºC

)

0.125 m

Multi-cracks

2D finite element model

10 cracks modeled

Multi-cracks

Crack #3

Multi-cracks

Von Mises Strain

1 crack (crack #3)

10 cracks

Multi-cracks

Stress concentration

Multi-cracks

10 cm spacing modeling

Multi-cracks

20 cm spacing 30 cm spacing

40 cm spacing 50 cm spacing

Multi-cracks

Influence of overlay thickness (10, 20 and 30 cm)

Single crack modeling

10 cm spacing

Multi-cracks

3D model

Multi-cracks

3D model

Multi-cracks

3D model

Thank you