5.Foamed-Bitumen-Stabilised-Pavements.ppt

Mix Design and field svaluation of FBSP

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TT1825 Mix design and field evaluation of foamed
bitumen stabilised pavements
December 2014

2. Need for cost-effective pavement
rehabilitation treatments
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3. Increasing use of foamed bitumen to stabilise
unbound granular bases of rural highways
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Commonly use
about 3% bitumen
and 1.5% quicklime

4. National procedures for design of FBS
treatments
•project commenced in July 2012
•two progress reports published
•completion June 2016
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•mix design
•distress modes
•improved Austroads
thickness design procedures

5. Collaboration is maximising research
outcomes
•research being guided by a Working Group comprising road
agencies and industry
•extensive collaborative of road agencies, industry and
ARRB
•laboratory testing by two experienced labs, Downer and
TMR
•road agencies and industries are contributing through the
construction of under-designed pavts
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6. Foamed bitumen (FB) mix design
•Existing mix design process in need of improvement
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7. Requirements for untreated material
•requirements for grading and plasticity of the untreated
material, generally accepted
•not the focus of research
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8. Amount of bitumen and lime determined from
indirect tensile modulus testing
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9. Department of Transport and Main Roads
(TMR) Queensland modulus requirements
•Austroads building on TMR experience over the last 15
years
•TMR lab mixes are compacted into 150 mm diameter
moulds and 10 kg Marshall hammer
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10. TMR mix requirements
•initial modulus 3 hours after lab compaction used as a
indicator of early-life rut resistance
•also undertake wheel tracking
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11. TMR mix requirements
•bitumen and lime content adjusted to satisfy requirements
for cured dry and wet modulus
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12. Issues being addressed in the research project
Need to harmonise test methods throughout Australia
•various compaction methods in use (e.g. gyratory, standard
Marshall, large Marshall)
•recently agreed that the interim Austroads method would be
large Marshall based on TMR experience
•various mixing and compacting moisture contents being
used
–70% standard Proctor OMC untreated material
–85% modified Proctor OMC untreated material
•some labs using quicklime other hydrated lime
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13. Effect of mixing moisture
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14. Research will lead to Austroads test method
and mix design procedure
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15. Issues being addressed in the research project
The most challenging issue is validation of usefulness of lab
moduli in materials characterisation/mix design.
Need to link lab moduli to field performance
•usefulness of initial moduli in evaluating early-life rut
resistance
•usefulness in cured dry and wet moduli in predicting long
term field performance
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The purpose of this project is:
•to improve and harmonise national mix design procedures
for bituminous stabilised materials
•to identify distress modes of bituminous stabilised
pavements from the trial sites.
•to improve the Austroads thickness procedures.
Purpose

17. Field performance
•to address the project objectives data on the field
performance of FBS pavement is required
•to obtain performance data during the research project (4
years), a number of under-designed pavements have been
constructed and are being monitored
•to date we have five trials
–Kwinana Freeway Perth (2010)
–Port Wakefield Road South Australia (2011)
–Kewdale Road, Welshpool Perth (2011)
–Calder Freeway, Woodend Victoria (early 2013)
–Newell Highway Bellata, NSW (late 2013)
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18. Summary of trials
Site Surface FBS
thickness
(mm)
Nominal
bitumen
content
(%)
Nominal
lime content
(%)
Kwinana FreewayOGA on
DGA
150 mm 3.5% 0.8%
hydrated lime
Port Wakefield
road
seal 150 mm and
200 mm
3% 1%
hydrated lime
Kewdale road DGA 100 mm and
150 mm
3% 0.8%
quicklime
Calder Freeway seal 150 mm 3.5% 1.5%
quicklime
Newell Highway seal 175 mm 3.5% 1.5%
quicklime
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19. Kwinana Freeway after FBS placement before
asphalt and GRS placed, 2010
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20. Port Wakefield Road 2011
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21. Calder Freeway Victoria under construction
March 2013
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22. Newell Highway 2013
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23. Sites tested during construction and
monitored for performance
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24. Proposed trial on Western Highway Victoria
Heavily trafficked road about 1-2 million ESA per year
200 mm depth FBS, anticipate fatigue after 2-3 years
Two binder contents 2.7% and 3.5%
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26. FINDINGS TO DATE
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27. Ravelling of Calder Freeway when pavement
was opened to traffic the day of construction
•ravelling next day
•may have been
affected by adding
additional material
late in construction to
adjust level to match
adjacent lane
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28. Cracking has been observed
•at commencement of trial doubts whether fatigue cracking
was a distress mode for FBS
•to date observed cracking at 2 of the 3 trial sites with seal
surfaces
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Port Wakefield Road, 18 months Calder Freeway, 18 months

29. Only one instance of rutting, when an old
asphalt patch was inadvertently stabilised
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30. Foamed bitumen and lime stabilisation
produces high modulus in situ
With high temp in
summer construction
enabled rapid water
loss, FBS cores can
be taken 7 days after
construction
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31. Modulus varies with markedly depth/density
•in situ modulus can decrease significantly with depth due to
lower densities
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32. Back-calculated moduli being monitored to
predict time to fatigue damage
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33. Issues being addressed to improve thickness
design
FBS design modulus
•currently values of 2000 – 3000 MPa are commonly used
•need improve process to determine the flexural design
modulus from the lab IDT moduli
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34. Data being obtained to improve determination of
design modulus
•relationship between moduli of lab specimens and moduli of
early-life field cores
•relationship to correct the lab moduli to the field densities
•relationship to adjust IDT modulus to a flexural modulus
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35. Issues being addressed to improve thickness
design
•currently fatigue relationship used is that for asphalt with a
reduced volume of binder
•given material contains 1-2% lime and the bitumen
distribution is different from asphalt this relationships needs
to be validated
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36. Summary
•research is being undertaken to improve Austroads
procedures for foamed bitumen stabilisaton:
–mix design
–thickness
•strong collaboration and involvement of road agencies and
industry will maximise research outcomes
•progress report published in 2014
•project is due for completion in June 2016
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