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SabitaBitumenDurabilityProject
Johan Muller
6 May 2008
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Background• RSA vs. USA and the rest of the globe
• SUPERPAVE
• Sprayed Seals vs. HMA
• Penetration vs. Performance graded
• Ageing vs. Durability
• RTFOT vs. PAV vs. RCAT vs. RTFOT (extended)
• Lab vs. Field (trials)
• Validation
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Ageing vs. Durability
Time
Per
form
ance
Par
amet
er e
.g.
G*
or
Vis
cBitumen B
Bitumen A
RTFO Ageing
Longer term ageing is required to differentiate between in service binder performance
PAV Ageing
Cracking threshhold
In Plant & Construction
In Service (5 to 10 yrs)
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Who is involved - Internally?
• Sabita funded Trevor Distin• Univ. Stellenbosch Prof Kim Jenkins• Tosas (research leader) Johan Muller• Tosas (project executor) Tertius Joubert• STFR ( Jacques van Heerden• STFR Gerhard Harmse• Natref allows us to utilise facilities• CSIR Esbe van Assen
• CSIR Benoit Verhaeghe
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• RSA vs. USA vs. Europe vs. Australia
• USA Prof Hussain Bahia Univ. Wisconsin
• Europe Prof Martin van de Ven TU Delft
• ARRB John Oliver / Peter Tredrea
• AAPA Walter Holcroft / Rob Vos?
Who is involved - Externally?
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Temperature Sweep
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
0 20 40 60 80 100 120
Temperature (°C)
delta
60/70 RTFOT |G*|·sin(delta) [Pa]
60/70 |G*|·sin(delta) [Pa]
60/70 RTFO 2h25 1 |G*|·sin(delta) [Pa]
60/70 RTFO 3h25 |G*|·sin(delta) [Pa]
60/70 RTFO 4h25 |G*|·sin(delta) [Pa]
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BBR COMPARISON
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 50 100 150 200 250 300
time
Def
lect
ion
(m
m)
Average 60/70 original d Deflection (mm)
Average 60/70 org d Deflection (mm)
Average 60/70 RTFOT d Deflection (mm) BBR COMPARISON
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300
time
Sti
ffn
ess
(Mp
a)
Average 60/70 original Measured Stif fness (Mpa)Average 60/70 org Measured Stif fness (Mpa)Average 60/70 RTFOT Measured Stif fness (Mpa)
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What is involved?• RTFOT, RTFOT, RTFOT Natref, Tosas STFR
• Penetration, R&B, Viscosity Natref
• PAV STFR
• RCAT TU DELFT?
• DSR STFR
• Bending Beam STFR
• FTIR Sastech
• SARA (HPLC at CSIR or IATROSCAN at Natref)
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What is involved?
3
4
5
6
7
0 2 4 6 8 10 12
Years since construction
Vis
cosi
ty a
t 45
ºC (
Lo
g P
a.s)
distress viscosity line
bitumen hardening curve (from hardening model)
intersection of hardening curve and distress line gives binder life
position depends on winter temperature
Courtesy of ARRB (John Oliver)
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What do we want to achieve?
• Develop an internationally acceptable durability protocol
• Relate Laboratory ageing to the actual ageing in the field
• Ultimately predict the difference in the behaviour of the GOOD, the BAD and the UGLY
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How do we want to achieve this
• Confirm CSIR durability protocol
• Refine the protocol where necessary
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What are the variables?
• Temperatures / time relationship
• Higher temperature faster ageing
• Longer time more ageing
• The optimum rate of ageing yielding – the same chemistry and – SAME STIFFNESS WHICH RESULTS IN
BITUMEN BECOMING TOO BRITTLE
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What is involved?BINDERS
Modified / Unmodified
SEALS HMA
Experimentation of ageing
Measure ageing effect with time
LaboratorySimulation
FieldTrials
CORRELATIONVALIDATION
IN-SERVICEPLANT