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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
1717
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
1919
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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