Transcript TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements December 2014 www.arrb.com.au Advancing safety and efficiency in transport through knowledge research | consulting.

TT1825 Mix design and field evaluation of foamed
bitumen stabilised pavements
December 2014
www.arrb.com.au
Advancing safety and efficiency in transport through knowledge
research | consulting | technology
Need for cost-effective pavement
rehabilitation treatments
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Increasing use of foamed bitumen to stabilise
unbound granular bases of rural highways
Commonly use
about 3% bitumen
and 1.5% quicklime
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National procedures for design of FBS
treatments
• mix design
• distress modes
• improved Austroads
thickness design procedures
• project commenced in July 2012
• two progress reports published
• completion June 2016
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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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Foamed bitumen (FB) mix design
• Existing mix design process in need of improvement
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Requirements for untreated material
• requirements for grading and plasticity of the untreated
material, generally accepted
• not the focus of research
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Amount of bitumen and lime determined from
indirect tensile modulus testing
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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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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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TMR mix requirements
• bitumen and lime content adjusted to satisfy requirements
for cured dry and wet modulus
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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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Effect of mixing moisture
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Research will lead to Austroads test method
and mix design procedure
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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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Purpose
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.
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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
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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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Summary of trials
Site
Surface
FBS
thickness
(mm)
Nominal
bitumen
content
(%)
Nominal
lime content
(%)
Kwinana Freeway
OGA 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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Kwinana Freeway after FBS placement before
asphalt and GRS placed, 2010
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Port Wakefield Road 2011
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Calder Freeway Victoria under construction
March 2013
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Newell Highway 2013
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Sites tested during construction and
monitored for performance
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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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FINDINGS TO DATE
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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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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
Port Wakefield Road, 18 months
Calder Freeway, 18 months
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Only one instance of rutting, when an old
asphalt patch was inadvertently stabilised
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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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Modulus varies with markedly depth/density
• in situ modulus can decrease significantly with depth due to
lower densities
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Back-calculated moduli being monitored to
predict time to fatigue damage
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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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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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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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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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