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