SabitaBitumenDurabilityProject
Johan Muller
6 May 2008
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
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)
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
• 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?
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]
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)
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)
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)
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
How do we want to achieve this
• Confirm CSIR durability protocol
• Refine the protocol where necessary
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
What is involved?BINDERS
Modified / Unmodified
SEALS HMA
Experimentation of ageing
Measure ageing effect with time
LaboratorySimulation
FieldTrials
CORRELATIONVALIDATION
IN-SERVICEPLANT