Stabilime
and Stabilco are both specialist
lime and cement soil stabilisation companies. Their scope
of work also includes construction and the supply and
distribution of binders used in the soil stabilisation
process. Soil stabilisation, in terms of pavement construction,
is the process of (usually insitu) pulverising and moisture
conditioning by mixing various binders with soil, compaction
and trimming as necessary. This improves soil characteristics
preferred for construction in terms of moisture content,
density, strength (CBR%), permeability, plasticity index
and shrink swell characteristics. Most material types,
clay through to crushed rock, are suitable for stabilisation.
Seeking advice early during the design/feasibility stage
enables planning for efficient use of stabilisation. Stabilime
and Stabilco have offices located
throughout the state. All our activities are quality assured,
and work to high standards of quality, health and safety
and environmental management.
Lime
and/or cement stabilisation is often used to improve the
properties of site won materials, to enable their use
in a pavement and other like areas, such as dam foundations
and building pad sites. Lime stabilisation of clay material
reduces entrance cracking, whilst increasing the hardness
of the material by up to ten times. The use of cement
as a binder, after lime, can further increase the strength
and durability towards that of concrete. Various binder
blends, away from lime and cement, such as slag or fly
ash, are commonly utilised for further benefit dependant
on site conditions and requirements.
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Saturated,
wet sites can be treated to provide a working platform
within a day for project continuation during wet periods/seasons.
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Stabilisation
recycles existing pavement by pulverising the existing
pavement to 25mm down. Lime and or cement or other
binders are then mixed with water as necessary. No
imported materials and increased production rates
means cost savings.
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Strength
gains often over CBR 15% or 5 times the previous strength
are the result of the realignment of particles and
adjustment of moisture content allowing compaction
at optimum moisture content.
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Reduce
Plasticity Index (PI) in cohesive materials. For example
a material with PI 20 will typically stabilise to
PI < 10, say 8. |
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Reduce
or eliminate the need for imported clay liner by stabilising
insitu materials. |
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Reduce
permeability. |
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Reduce
Linear Shrinkage rate up to 10%. |
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Environmental
benefits of reduced geotextile, borrow pit clay and
quarry import. |
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Additional
environmental benefits from reducing extra excavation
and disposal by modification to suitable material. |
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Improved structural stability through realignment
of soil particles by ionic exchange between clay and
lime. |
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Increased
Strength and durability. |
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Reduced
dispersion means reduced dispersion piping failure
and increased erosion protection. |
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Pulverisation
to 40mm down of clay, extremely weathered limestone,
mudstone and siltstone provides smaller diameter conglomerates
and homogenous material throughout the stabilised
layer eliminating lenses, streaks, rock fissures and
faults providing reduced seepage. |
Note
that there are many variations of lime available but only
quicklime is considered suitable for lime stabilisation
in the pavement construction industry and general field
construction activities. Quicklime is calcium oxide (CaO)
supplied commercially in a dry powder form. Agriculture
Lime is a calcium carbonate (CaC03) and not suitable for
pavement construction. Hydrated Lime is calcium hydroxide
(Ca(OH)2) often used in the laboratory for lime saturation
testing, not generally used on site for pavement construction.
Hydrated
lime (calcium hydroxide), is produced by reacting water
with quicklime (calcium oxide). CaO + H2O => Ca(OH)2.
When calculated using the atomic weights, this converts
practically to 5t Quicklime + 3t Water => 7t Hydrated
lime + 1t Water Evapouration.
The
pozzolanic reaction between lime with water and the silica
and alumina in clay results in an ionic exchange, which
permanently realigns the clay particles forming friable
conglomerates. The new alignment of the particles provides
less ability for the clay to absorb water around the particles.
This makes the clay more waterproof, less expansive and
therefore reduces the plasticity and linear shrinkage.
The PI is often more than ½ and the shrinkage is
often 10% of what it was. Practically this results in
improved permeability less shrinkage cracking providing
less chance of piping failure and seepage.
In
a lime saturated environment (typically 3% to 4% quicklime),
the clay-alumina and clay-silica become available to react
with the free calcium to form calcium aluminates or silicates.
The pozzolanic reaction is illustrated by the following
equations:
| Ca2+
+ OH- + Available Clay Aluminium |
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Calcium
Aluminate Hydrate (CAH) |
| Ca2+
+ OH- + Available Clay Silica |
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Calcium
Silicate Hydrate (CSH) |
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