1. Overview of Foam Bitumen Contracts
Undertaken in Far North Queensland
Craig Gordon – Cairns Office
RTA Northern Region
17th
March 2010
2. SCOPE
• Fundamentals of Foam Bitumen Pavements
• Projects Undertaken
• Construction Methods Used
3. Foam Bitumen Stabilised Pavements
• What is Foam Bitumen Stabilised Pavements.
– It is a mixture of gravel, lime or cement, air, water and bitumen
– When air, water and bitumen are mixed with each other the
mixture expands greater than 10 times its original volume and
forms a fine mist or foam
– This foam is sprayed into the drum where it coats the fine
particles
– As the foam collapses most of the water is lost through steam
– The residual bitumen then has properties similar to its original
state and is well dispersed through the matrix in very small
droplets
– The bitumen droplets are attracted to and coat the finer
particles, forming a uniform matrix that effectively binds the
mixture together.
5. Where to Use the Foam Bitumen Process
• A pavement that has been repeatedly patched to the
extent that pavement repairs are no longer cost
effective
• A weak granular base overlays a reasonably strong
subgrade
• Granular base is too thin to consider cementitious
binders
• Alternative to full depth asphalt in moderate to high
trafficked roads
• Unfavourable wet cyclic conditions
• To complete the rehabilitation quickly to prevent
disruption to businesses, residents and public
7. Contracts Undertaken
• Within the Peninsula District of North Queensland, a number of
Foam Bitumen contracts have been carried out. The majority of
these projects have been on the Bruce Highway where the roads
have been affected by flood damage.
• The district is now also including foam bitumen pavements in new
pavements / reconstructed pavements.
• Foam Bitumen Pavements appear to be the desired choice for the
major highways in the District, Bruce, Palmerston, Captain Cook.
• The Cairns Regional Council has also done some minor works with
Foam Bitumen Stabilisation.
• Mackay Regional Council have also awarded DEW a foam
bitumen contract which we are currently undertaking.
8. Contracts Undertaken
• Department of Main Roads, Queensland (since
November 2008 to current)
– Bruce Highway – approximately 2.5km (El Arish)
– Bruce Highway – approximately 3.5km (Mourilyan)
– Bruce Highway – approximately 3.5km (Cardwell)
– Palmerston Highway – approximately 5km
– Palmerston Highway – approximately 2km
– Palmerston Highway – approximately 0.7km
– Palmerston Highway – approximately 3.5km
• Other Projects
– Mackay Regional Council Flood Damage Package 7 (Various
council roads)
9. Foam Bitumen
• Basic design of the pavements is to incorporate an
overlay, with 2% lime or 1.5% of cement and 3.5% of
bitumen.
• An overlay is only used when required and generally
consists of between 50mm and 100mm of Type 2.1
Gravel.
• The use of the overlay was for shape correction and
also to increase the quality of the pavement material,
ie gradings.
10. Foam Bitumen
• Design Considerations employed by Main Roads:
– Design period
– Design Traffic
– Subgrade Material Properties
– Pavement Material Properties
– Environmental Influences
– Construction and Maintenance Procedures
– Drainage
11. Benefits and Limitations
Benefits:
– Increased strength over granular pavement materials
– Relatively quick construction method
– Lower costs than Reconstruction
– Trafficked immediately (in the right conditions)
– Can be trafficked without a seal
– Decreased susceptibility to moisture during
construction.
– Can be reworked several days after final trimming
without extra binder
12. Benefits and Limitations
Limitations:
– Requires a suitable grading of fines in the pavement
material
– Purpose built equipment and experienced operators
are required
– Cost is greater than cement stabilisation
– Not suitable for all pavements (some pavements
show low strength gain, slow strength gain an
unsuitable grading)
13. Secondary Stabilising Agent and
Foaming Agent
• Secondary Stabilising Agent:
– Usually consists of cement or lime, lime is the preferred option,
although cement is cheaper
– Specified working time (4 hours) commences upon
incorporation, although bitumen is then required to be
incorporated within the next 1.5 hours
– Incorporated 50mm above the target depth.
– Purpose for secondary stabilising agent:
• Assist in strength increase
• Assist in dispersion of bitumen throughout mix
• Improves mix workability
• Reduces the plasticity Index
17. Secondary Stabilising Agent and Foaming
Agent
• Foaming Agent
– A proprietary product is used
– Used to combat the anti foaming agent that has been put into
bitumen for transport reasons
– A maximum of 2% by mass should be added
– Generally we have found 0.5% is adequate to achieve half life
and expansion ratios
– Assists in the dispersion of bitumen to coat each particle of the
pavement
– Essential to be used, as bitumen will naturally foam when hit
with water, although the dispersion is still not as adequate
without the foaming agent
20. Things to consider with
Foamed Bitumen Stabilisation
• Safety is paramount when working in any environment, especially
under traffic and when using hot bitumen binder
• Typical application rates of foam bitumen are between 2-4%
bitumen with the addition of a binder i.e. lime or cement, around
about the 2% mark
• Sufficient pavement testing including testing of the subgrade is
crucial when determining mix design and potential for using foam
bitumen. Testing can cost approx. $3000 - $4000 per test, although
the bitumen savings it could produce are considerable
• Sealing rates over foam bitumen pavements are usually reduced
by at least 10% compared to normal pavements, common
problems are bleeding of seals and potential instability of asphalt
layers.
• A foaming agent is a must when foaming bitumen
21. Things to consider with
Foamed Bitumen Stabilisation
• Construction times are very important
• Moisture content of the pavement is important, and
generally in the range 60-80% of optimum
• Experienced construction teams are essential when
undertaking foam bitumen
• Although method is less susceptible to wet weather
than other pavements, work in wet weather should be
avoided as moisture can become trapped in lower
layers of pavement causing problems with compaction
• Allowing traffic on the surface prior to primer sealing is
not desirable, as the fines on the surface contain
bitumen, which will in turn get stuck to cars.
23. Construction Methods
• Plant and Labour Crew
– Traffic Control
– Project Manager
– Supervisor
– Wirtgen WR2000 or WR2500 (Foam Bitumen Capabilities)
– Additional Mixer if required for pulverisation, cement / lime
incorporation
– Grader
– Loader (If Overlay)
– Trucks (If Overlay)
– Bitumen Tankers (Capable of attaching to the mixers bar)
– Watercarts
– Rollers (18t for up to 250mm, 21 tonne up to 300mm) include Pad foot,
Smooth Drum and Multi Tyred Rollers
– Generally also require 3-4 additional laborers on the ground for Quality
Assurance checks and day to day tasks
24. Construction Methods
• Methodology
– Generally, traffic control is set up to close 1 lane approx 500m
in length
– Place Overlay
– Pulverize pavement
– Spreading of lime / cement
– Mixing of lime /cement and water
– Incorporation of foamed bitumen
– Final Trimming of Pavement
– Sealing works
25. Production rates
• Indicative production rates achieved (daily/10 hr day)
on a 250 mm pavement with 50 mm overlay, 8 kg/m2
cement and 18.4 kg /m2 bitumen.
• 1200 m2 to 2,400 m2 per day (under one lane traffic).
• Production constraints
• Supply of materials i.e. gravel, bitumen, powder,
aggregates and additives.
• Stockpiles sites if required
• Traffic
• Weather
• Machine breakdowns
