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Asphalt Recycling and Materials Asphalt Recycling and Materials Re-use in Asphalt PavementsRe-use in Asphalt Pavements

L’Aquila, Italy, 27 – 29 June 2007L’Aquila, Italy, 27 – 29 June 2007

Hussain A KhalidHussain A KhalidUniversity of Liverpool, U.K.University of Liverpool, U.K.

22

ContentsContents• Introduction – outline of current recycling Introduction – outline of current recycling

position in UK;position in UK;• Experience with re-use of two materials in Experience with re-use of two materials in

asphalt:asphalt:– Binder additive; andBinder additive; and– Aggregate replacementAggregate replacement

• FunctionalityFunctionality• ChallengesChallenges

33

Recycling – Is it all worth it?Recycling – Is it all worth it?

44

• In the UK, asphalt recycling is common, In the UK, asphalt recycling is common, encouraged and is specified by national encouraged and is specified by national standards.standards.– In-situ recycling comprises three processes:In-situ recycling comprises three processes:

• RepavingRepaving• RemixingRemixing

• Retread – Retread – Cold (may adopt emulsion or foam Cold (may adopt emulsion or foam bitumen)bitumen)

IntroductionIntroduction

Hot – Wirtgen Machine

55

IntroductionIntroduction

– Plant recycling (off-site)Plant recycling (off-site)•Hot recycled materials in modified batch Hot recycled materials in modified batch

plants have been used. More recently, cold plants have been used. More recently, cold recycled materials have evolved using recycled materials have evolved using bitumen emulsion or foam.bitumen emulsion or foam.

66HD35/04 Design Manual for Roads & Bridges

Provisions for use of secondary and recycled materials in UK pavements

77

Recent and current research on Recent and current research on materials re-use in asphalt materials re-use in asphalt

pavementspavements

88

Recycled rubber (wet process)Recycled rubber (wet process)

99

Incinerator

Stack gases

Bottom ash

Fly ash

Domestic waste

5-8,000 cubic meters per tonne

10-30 kg per tonne

250-350 kg per tonne

Incinerator Bottom Ash Aggregate Incinerator Bottom Ash Aggregate (IBAA)(IBAA)

1010

Crumb tyre rubber - Crumb tyre rubber - rheologyrheology

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E-04 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06

Frequency (aT* Hz)

G*(P

a)0% CRM5% CRM10%CRM

100pen KSRTref = 25 0C

1111

Crumb tyre rubber - Crumb tyre rubber - fatiguefatigue

1E+04

1E+05

1E+06

1E+07

1E+08

1E+02 1E+03

Initial Strain (µ m/m)

Num

ber o

f Cyc

les

...

Neat SMA5% CRM10% CRM

1212

Crumb tyre rubber - Crumb tyre rubber - ruttingrutting

Temperature (oC) 45 60

Binder Content

(%)

CRM Content

(%) Rut Depth (mm)

Rutting Rate (mm/hr)

Rut Depth (mm)

Rutting Rate (mm/hr)

5.5 5.5 6

0 5

10

1.9 1.2 1.0

0.53 0.46 0.21

2.5 2.2 1.9

0.65 0.62 0.11

14mm SMA including 50 Pen binder

1313

Crumb tyre rubber - Crumb tyre rubber - cracking resistancecracking resistance

Notched prismatic beam specimen

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8

Deflection (m m )

Load

(kN

)

FRT1 a/W=0.3FRT2 a/W=0.4FRT3 a/W=0.5

0.00

0.50

1.00

1.50

2.00

DBM 0%

DBM 10% Truck

DBM 10% Car

SMA 0%

SMA 5% Truck

SMA 10% Truck

Mixture Type

J Ic (N

.mm

-1)..

.

-5oC

60mm/min10mm/min

1414

Crumb tyre rubber – Crumb tyre rubber – site trialsite trial

1515

Rubber asphalt - ChallengesRubber asphalt - Challenges

• No cross-linking between rubber and No cross-linking between rubber and bitumen – bitumen – storage problemsstorage problems

• Long-term performance – Long-term performance – ageingageing• Potential for recycling - Potential for recycling - recyclabilityrecyclability• Cost implications – Cost implications – legislation/tax-relieflegislation/tax-relief

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IBAA in asphaltIBAA in asphalt• IBAA has been used to replace virgin IBAA has been used to replace virgin

(limestone) aggregate in an asphalt (limestone) aggregate in an asphalt mixture suitable for base or binder coursemixture suitable for base or binder course

0

20

40

60

80

100

0.01 0.1 1 10 100Seive Sizes (mm)

% P

assin

g

Lower binder coarse limits

Upper binder coarse limits

lower road base limits

upper road base limits

Limestone Conrol Blend

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Mix design – (HMA)Mix design – (HMA)

4.0

6.0

8.0

10.0

12.0

3.0 3.5 4.0 4.5 5.0 5.5

Binder Content (%)

VIM

(%)

500

1000

1500

2000

3.0 3.5 4.0 4.5 5.0 5.5

Binder Content (%)

ITS

M @

20 0 C

(MP

a)

Limestone control mixture

5.0

10.0

15.0

20.0

4 5 6 7 8 9

Binder Content (%)

VIM

(%)

30% IBAA60% IBAA80% IBAA

1000

1500

2000

2500

4 5 6 7 8 9

Binder Content (%)

ITSM

@ 20

0 C

(MPa

)IBAA replacement at different levels

100 Pen binder

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Mix design – cold asphaltMix design – cold asphalt

11.0

12.0

13.0

6.5 7.0 7.5 8.0 8.5 9.0

Binder Content (%)

VIM

(%

)

600

700

800

900

6.5 7.0 7.5 8.0 8.5 9.0

Binder Content (%)

ITS

M @

20

0 C

(M

Pa

)

14.0

15.0

16.0

17.0

6.5 7.0 7.5 8.0 8.5 9.0

Binder Content (%)

VIM

(%

)

800

1000

1200

6.5 7.0 7.5 8.0 8.5 9.0

Binder Content (%)IT

SM

@ 2

0

0 C (

MP

a)

60% IBAA

80% IBAA

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Moisture sensitivity Moisture sensitivity (durability)(durability)

0

20

40

60

80

100

3 4 5 6 7 8 9

Bindre Content (%)

Ret

aine

d S

tiffn

ess

(%)

Control mix30% IBAA mix

60% IBAA mix80% IBAA mix

Mixtures saturated, immersed in water at 60oC for 6 hrs, then in water at 5oC for 16 hrs – 3 cycles

2020

Challenges - problemsChallenges - problems

• Viability of IBAA mixtures;Viability of IBAA mixtures;• Durability.Durability.

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