performance evaluation of hot recycled mixtures containing

Arianna Stimilli, Ph.D. 1

Polytechnic University of Marche – Faculty of Engineering

6th INTERNATIONAL CONFERENCE BITUMINOUS MIXTURES AND PAVEMENTS

Thessaloniki, Greece, 10 - 12 June, 2015

Performance evaluation of hot recycled mixtures containing SBS modified binder

Arianna Stimilli - Gilda Ferrotti - Daniele Radicioni - Francesco Canestrari





Introduction

Objectives

Experimental Program

Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Step 1 Step 3Step 2

Laboratory characterization of

BINDER LAYERS with 40% RAP

used in Italian motorways





Reclaimed Asphalt

Environmental benefits

Less construction waste

Save money





Reclaimed Asphalt

Environmental benefits

Less construction waste

Save money

Increasing demand of HIGH AMOUNT OF RAP in bituminous mixtures

Oxidation of RAP binder

RAP aggregate gradation

Virgin and aged binder blending

Polymers in RAP binder

…





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Evaluation of the effects caused by 40% RAP content on the

mechanical performance of hot recycled mixtures, analyzing

the effects due to the use of DIFFERENT VIRGIN POLYMER

MODIFIED BINDERS and DIFFERENT TOTAL BINDER CONTENTS.

Objectives

Goal: +15% of RAP in hot recycled mixtures

CURRENT % RAP GOAL % RAP





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Mixtures

Mixture % RAP % total binder Type of binder

REF 25 4,8 3,8% SBS

5,0%S 40 5,0 1,8% SBS

5,2%S 40 5,2 1,8% SBS

5,0%H 40 5,0 3,8% SBS

5,2%H 40 5,2 3,8% SBS

Prepared in accordance with the Italian

specification for motorway binder courses





Mixtures


REF 25 4,8 3,8% SBS

5,0%S 40 5,0 1,8% SBS

5,2%S 40 5,2 1,8% SBS

5,0%H 40 5,0 3,8% SBS

5,2%H 40 5,2 3,8% SBS





Mixtures


REF 25 4,8 3,8% SBS

5,0%S 40 5,0 1,8% SBS

5,2%S 40 5,2 1,8% SBS

5,0%H 40 5,0 3,8% SBS

5,2%H 40 5,2 3,8% SBS

VIRGIN + RECLAIMED BINDER

Not all the aged binder coming from RAP

takes part in the blending process





0

10

20

30

40

50

60

70

80

90

100

0,01 0,1 1 10 100

Pa

ss

ing

[%

]

Sieve opening [mm]

REF

40% RAP mixes_lab mix design

Grading envelope

RAP aggregate

Virgin aggregate

Lim

10/20

Lim

4/10

Lim

0/4Filler

RAP

8/16RAP

0/8

RAP

0/16

25% RAP 0/16

15% RAP 8/16 + 25% RAP 0/8

Step 1: AGGREGATE GRADING CURVE OPTIMIZATION

BAILEY METHOD

RAP:

from old motorway

pavements





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Step 2: MECHANICAL CHARACTERIZATION

Cyclic triaxialcompression test

[UNI EN 12697-25]

Effects related to high RAP percentages

Stiffness

Ru

ttin

gT

he

rma

l cra

ckin

g

Fatigue

Cyclic uniaxialcompression test

[AASHTO TP 79-09]

Repeated Load Indirect Tensile Test[BS DD ABF]

ITSM[EN 12697-25] Semi Circular

Bending test[UNI EN 12697-44]

Compactability and volumetric properties





SPECIMENS PREPARED IN LAB SIMULATING IN PLANT PRODUCTION:

Mixing T = 170°C Compaction T = 160°C Target air voids content = 3.5% D = 150 mm H = 170 mm

Step 2: MECHANICAL CHARACTERIZATION

Mixture SCBPermanent

Deformation

Complex

ModulusITSM

Crack

initiation

REF 4 3 2 6 6

5.0%S 4 3 2 6 6

5.2%S 4 3 2 6 6

5.0%H 4 3 2 6 6

5.2%H 4 3 2 6 6

TOTAL 20 15 10 30 30





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Compactability and aggregate packingCOMPACTION ENERGY INDEX (CEI)

Compaction Energy Index (CEI) represents the work applied by the roller forcompacting the mixture to the require density just before traffic opening

Gyrations 8th gyration

% G

mm

Final bulk density

Compaction Energy Index

(CEI)

Final gyration

92% of






0

100

200

300

400

500

600

REF 5.0%S 5.2%S 5.0%H 5.2%H

Co

mp

ac

tio

n E

ne

rgy I

nd

ex

(C

EI)

D = 150 mm

25% RAP

WORST

COMPACTABILITY BAILEY METHOD

RAP FRACTIONING

40% RAP






0

100

200

300

400

500

600

REF 5.0%S 5.2%S 5.0%H 5.2%H

Co

mp

ac

tio

n E

ne

rgy I

nd

ex

(C

EI)

D = 150 mm

LOW MODIFIED HIGH MODIFIED

LOWER VISCOSITY for the low modified binder





IMAGE ANALYSIS

RGB Gray scale BW

2-DIMENSIONAL IMAGES OF MIXTURES SECTIONS

N. OF CONTACT POINTS

PROXIMITY ZONE LENGTH





Compactability and aggregate packingCOMPACTION ENERGY INDEX (CEI) AND IMAGE ANALYSIS

D = 150 mm

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0

100

200

300

400

500

600

REF 5.0%S 5.2%S 5.0%H 5.2%H

N.

of

co

nta

ct

po

ints

Co

mp

ac

tio

n E

ne

rgy I

nd

ex

(C

EI)

CEIProximity points

• LOWEST PROX. PT

• HIGHEST CEI

• HIGHEST PROX. PT

• LOWEST CEI





Stiffness

Cyclic uniaxial compression test – Complex modulus

5 TEMPERATURES: 10 – 20 – 30 – 40 – 50 °C

SINUSOIDAL LOAD WAVES @ 6 FREQUENCIES: 0.1 – 0.3 – 1 – 3 – 10 – 20 HZ

CONTROL STRESS MODE WITH AXIAL DEFORMATION: 50 με





StiffnessNon thermo-rheologically simple behavior of all mixtures

(Cole-Cole diagram)

RAP PMB

0

2000

4000

6000

0 10000 20000 30000 40000

Loss M

odulu

sE

2[M

Pa]

Storage Modulus E1 [MPa]

T = 10 °C

T = 20 °C

T = 30 °C

T = 40 °C

T = 50 °C

REF

0

2000

4000

6000

0 10000 20000 30000 40000

Loss M

odulu

sE

2[M

Pa]

Storage Modulus E1 [MPa]

T = 10 °C T = 20 °C

T = 30 °C T = 40 °C

T = 50 °C

5.2%S





Stiffness

1,0E+02

1,0E+03

1,0E+04

1,0E+05

1,0E-08 1,0E-06 1,0E-04 1,0E-02 1,0E+00 1,0E+02 1,0E+04 1,0E+06

No

rm o

f th

e c

om

ple

x m

od

ulu

s|E

*| [

MP

a]

Frequency [Hz]

Tref = 20 °C

Complex modulus master curve

High modifiedbinder

Low modifiedbinder

REF





Resistance to crack propagation

D notch (depth = a)

W

ligament area

ENERGY APPROACH: the fracture energy

G represents the work required to increase

the fractured surface until complete failure

SCB (Semi-Circular Bending)






0,0

0,5

1,0

1,5

2,0

0

10

20

30

40

50

60

REF 5.0%S 5.2%S 5.0%H 5.2%H

Fra

ctu

reE

nerg

y G

[kJ/m

2]

Fra

ctu

re T

ou

gh

ness K

[N

/mm

1.5]

Fracture toughness K

Fracture Energy G

T = 10°C

Positive contribution

of aged SBS

Ductility

Crack resistance

REF






0,0

0,5

1,0

1,5

2,0

0

10

20

30

40

50

60

REF 5.0%S 5.2%S 5.0%H 5.2%H

Fra

ctu

reE

nerg

y G

[kJ/m

2]

Fra

ctu

re T

ou

gh

ness K

[N

/mm

1.5]

Fracture toughness K

Fracture Energy G

T = 10°C

LOW MODIFIED:better aggregate packing

(CEI and prox. pt)

Ductility

Crack resistance

REF





Resistance to permanent deformation

TEMPERATURE: 40 °C

CONFINING PRESSURE: 50 kPa

AXIAL STRESS: 200 kPa

Block-pulse load

CYCLIC TRIAXIAL COMPRESSION TEST





0 2000 4000 6000 8000 10000

Cu

mu

lati

ve

axia

l str

ain

εn

[%

]

Number of load repetitions n

fc1

A

εn = A + fc ∙ n

(quasi) linear part

Mixturefc

[µstrains/cycles]

REF 0.071

5.0%S 0.047

5.2%S 0.043

5.0%H 0.039

5.2%H 0.023


CREEP RATE

+15% RAP

Bailey Method

RAP fractioning






0 2000 4000 6000 8000 10000

Cu

mu

lati

ve

axia

l str

ain

εn

[%

]


fc1

A

εn = A + fc ∙ n

(quasi) linear part

Mixturefc

[µstrains/cycles]

REF 0.071

5.0%S 0.047

5.2%S 0.043

5.0%H 0.039

5.2%H 0.023

Stiffer

Higher SBS content

(more elasticity)






0 2000 4000 6000 8000 10000

Cu

mu

lati

ve

axia

l str

ain

εn

[%

]


fc1

A

εn = A + fc ∙ n

(quasi) linear part

Mixturefc

[µstrains/cycles]

REF 0.071

5.0%S 0.047

5.2%S 0.043

5.0%H 0.039

5.2%H 0.023

Improved performance even

with a LOW MODIFIED BINDER

(BEST AGGREGATE PACKING)





Resistance to repeated loading

TEMPERATURE: 20 °C

AT LEAST 3 STRESS LEVELS PER EACH MIXTURE

RISE TIME: 124 ms

REPEATED INDIRECT TENSILE TEST

124 ms






ε = 544.47N-0.191R² = 0.736

ε = 718.55N-0.189R² = 0.847

ε = 671.06N-0.188R² = 0.763

ε = 527.19N-0.177R² = 0.957

ε = 572.02N-0.180R² = 0.902

30

300

1000 10000 100000

ε[με]

Number of cycles to failure

REF

5.0%S

5.2%S

5.0%H

5.2%H

T = 20°C

REF

5.0%S 5.2%S

5.0%H 5.2%H

LOW MODIFIED

HIGH MODIFIED

REF






30

300

1000 10000 100000

ε[με]


REF

5.0%S

5.2%S

5.0%H

5.2%H

T = 20°C

LOW MODIFIED

HIGH MODIFIED

REF

40% RAP25 % RAP

IMPROVED ADHESION





30

300

1000 10000 100000

ε[με]


REF

5.0%S

5.2%S

5.0%H

5.2%H

T = 20°C


Higher ductility (SCB)

Better aggregate packing and longer

path length (IMAGE ANALYSIS)

Less stiff

HIGH MODIFIED LOW MODIFIED





Introduction

Objectives


Materials

Testing

Results & Analysis

Conclusions

OUTLINE





Conclusions (1/2)

40% RAP mixtures demonstrated:

higher workability and compactability;

Improved aggregate packing;

Acceptable stiffness values (especially by using a softer binder);

Higher resistance to crack formation and propagation;

Higher ductility;

Better performance to permanent deformation and fatigue.

40% RAP mixtures provided equal or even better performance than the reference mixture, regardless of the parameter considered





Conclusions (2/2)

Use of a SOFTER BINDER guarantees a better interaction with highamounts of RAP.

5.0% of total binder content appears adequate to optimize the 40%RAP mixture behavior.

Amounts of RAP up to 40% are suitable for the production of newbituminous materials, when a specific and detailed mix design isperformed.

The implementation of the Bailey Method as a tool for optimizing theaggregate packing together with the fractioning of RAP in two sizesrepresent a useful and effective strategy to overcome the usage of highRAP content.

performance evaluation of hot recycled mixtures containing

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