Asphalt Recycling and Materials Re-use in Asphalt Pavements

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Asphalt Recycling and Materials Asphalt Recycling and Materials

Re-use in Asphalt Pavements Re-use in Asphalt Pavements

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

Hussain A Khalid Hussain A Khalid

University of Liverpool, U.K.

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Contents Contents

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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

•

^Challenges^Challenges

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Recycling – Is it all worth it?

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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.

– In-situ recycling comprises three processes:In-situ recycling comprises three processes:

• ^Repaving^Repaving

• ^Remixing^Remixing

• ^{Retread –}^{Retread –} Cold (may adopt emulsion or foam Cold (may adopt emulsion or foam

bitumen)bitumen)

Introduction Introduction

Hot – Wirtgen Machine

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Introduction Introduction

– 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.

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HD35/04 Design Manual for Roads & Bridges 6

Provisions for use of secondary and recycled

materials in UK pavements

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Recent and current research on Recent and current research on

materials re-use in asphalt materials re-use in asphalt

pavements

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Recycled rubber (wet process)

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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)

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Crumb tyre rubber -

Crumb tyre rubber - rheology rheology

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*(Pa)

0% CRM 5% CRM 10%CRM 100pen KSR

T_ref= 25 ⁰C

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Crumb tyre rubber -

Crumb tyre rubber - fatigue fatigue

1E+04 1E+05 1E+06 1E+07 1E+08

1E+02 1E+03

Initial Strain (µm/m) Number of Cycles ...

Neat SMA 5% CRM 10% CRM

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Crumb tyre rubber -

Crumb tyre rubber - rutting rutting

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

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Crumb tyre rubber -

Crumb tyre rubber - cracking resistance cracking resistance

Notched prismatic beam specimen

0 0.5 1 1.5 2 2.5 3

0 1 2 3 4 5 6 7 8

De fle ction (m m )

Load (kN)

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

JIc (N.mm-1 )...

-5^oC

60mm/min

10mm/min

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Crumb tyre rubber –

Crumb tyre rubber – site trial site trial

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Rubber asphalt - Challenges Rubber asphalt - Challenges

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No cross-linking between rubber and No cross-linking between rubber and bitumen –

bitumen – storage problemsstorage problems

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Long-term performance – Long-term performance – ageingageing

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Potential for recycling - Potential for recycling - recyclabilityrecyclability

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Cost implications – Cost implications – legislation/tax-relieflegislation/tax-relief

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IBAA in asphalt IBAA in asphalt

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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 course mixture suitable for base or binder course

0 20 40 60 80 100

0.01 0.1 1 10 100

Seive Sizes (mm)

% Passing

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 (%) ITSM @ 200 C (MPa)

Limestone control mixture

5.0 10.0 15.0 20.0

4 5 6 7 8 9

Binder Content (%)

VIM (%)

30% IBAA 60% IBAA 80% 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 asphalt Mix 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

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

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 (%)

Retained Stiffness (%)

Control mix 30% IBAA mix 60% IBAA mix 80% IBAA mix

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

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Challenges - problems Challenges - problems

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Viability of IBAA mixtures;Viability of IBAA mixtures;

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Durability.Durability.

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