1. TT1825 Mix design and field evaluation of foamed bitumen stabilised pavements
December 2014
Advancing safety and efficiency in transport through knowledge

2. Need for cost-effective pavement rehabilitation treatments

3. Commonly use about 3% bitumen
Increasing use of foamed bitumen to stabilise unbound granular bases of rural highways
Commonly use about 3% bitumen
and 1.5% quicklime

4. 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

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

6. Foamed bitumen (FB) mix design
Existing mix design process in need of improvement

7. Requirements for untreated material
requirements for grading and plasticity of the untreated material, generally accepted
not the focus of research

8. Amount of bitumen and lime determined from indirect tensile modulus testing

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

10. TMR mix requirements
initial modulus 3 hours after lab compaction used as a indicator of early-life rut resistance
also undertake wheel tracking

11. TMR mix requirements
bitumen and lime content adjusted to satisfy requirements for cured dry and wet modulus

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

13. Effect of mixing moisture

14. Research will lead to Austroads test method and mix design procedure

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

16. 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.

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)

18. 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
0.8% quicklime
Calder Freeway
1.5% quicklime
Newell Highway
175 mm

19. Kwinana Freeway after FBS placement before asphalt and GRS placed, 2010

20. Port Wakefield Road 2011

21. Calder Freeway Victoria under construction March 2013

22. Newell Highway 2013

23. Sites tested during construction and monitored for performance

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%

26. Findings to date

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

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
Port Wakefield Road, 18 months
Calder Freeway, 18 months

29. Only one instance of rutting, when an old asphalt patch was inadvertently stabilised

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

31. Modulus varies with markedly depth/density
in situ modulus can decrease significantly with depth due to lower densities

32. Back-calculated moduli being monitored to predict time to fatigue damage

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

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

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

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