Lime Stabilisation Specialists for Victoria
With over twenty years experience throughout Australia, New Zealand and the South Pacific and its large fleet of modern, purpose built stabilisation plant, Hiways offers unparalleled performance in this highly specialised industry.
The Romans undertook lime stabilisation of pavement soils some 2000 years ago, the results of which are still clearly obvious throughout Europe today. The process has since been highly mechanised and reformed but the principles remain the same.
Lime stabilisation is the most common type of subgrade stabilising. It involves the spreading of calcium oxide (CaO) which is then watered (slaked) to form calcium hydroxide (Ca(OH)2) and mixed into the subgrade soil. The calcium hydroxide reacts with the aluminate and silicate minerals found in almost all clayey soils. The resulting calcium silicate and calcium aluminate hydrates are very similar to those produced by the hydration of Portland cement and produce significant increases in soil strength over a relatively short time period.
Subgrades are generally stabilised with lime or cement or a combination of the two. Generally cohesive, silty, clayey soils will react more effectively with lime while sandy soils will react best with cement. Soils will at times be a combination of silt, sand and clay and may require stabilising with a Lime/Cement blend.
Depending on the reactiveness of the soil, strength gains of up to 20 times are often achievable. This strength increase is one of a number of benefits subgrade stabilisation offers and enables a pavement to be designed with reduced depths of subbase and basecourse aggregates.
To determine the reactivity of a soil, testing, which generally involves laboratory CBR tests on the natural soil and then with stabilising binders added, is undertaken. The results are compared and the reactiveness and CBR strength increases are assesed.
The subgrade stabilisation process involves the following:
- Spreading a specified application of either lime or cement (or a blend of both) on the prepared subgrade via purpose built precision spreader trucks.
- Applying sufficient water to the binder(s) for slaking/hydrating via purpose built pressurised water carts, typically with side mounted spray bars.
- Mixing the binder with a purpose built stabilising machine to a specified depth achieving a specified degree of mixing and soil particle size.
- Compacting the mix with a heavy, vibrating padfoot roller.
- Trimming to final design levels using a grader and smooth drum roller.
Hiway Stabilizers Australia, with the backing and transfer of expertise from Hiways New Zealand are one of the most experienced specialist stabilisation providers in Australasia. With the largest fleet of stabiliser machines in Australasia consisting of a blend of Wirtgen and Komatsu models, Hiways are well placed to meet demand.
The Benefits of a Stabilised Subgrade:
A stabilised subgrade is a much more stable and durable subgrade that is resistant to volume and strength changes caused by moisture and temperature variations.
Stabilising will produce a subgrade layer with increased strength that will act as an "anvil" when compacting subsequent aggregate layers thereby enabling higher densities to be achieved in the aggregate layers, realising the aggregate's (and final pavement's) full potential.
Reduced Pavement Depth:
By stabilising a subgrade, an increased design CBR strength can be used with resulting reductions in overlying aggregate layer depths for an equivalent pavement design life and traffic loading. Reduced aggregate layer depths result in reduced aggregate volumes, associated costs savings, reduced transport costs, reduced time and conservation of aggregate resources.
Strength and Stiffness:
Increasing the strength and stiffness of a subgrade will provide a much more stable platform that is resistant to deformation and failure caused by construction traffic and requires less effort to trim to final subgrade levels.
Clayey soils have a high plasticity index, (the range of water content at which the soil maintains a plastic state), lime stabilising reduces the plasticity index, increases the workability of the soil and its ability to maintain its desired profile under loading.
A stabilised subgrade will form a moisture barrier that will protect the overlying aggregate layers from capillary action and the underlying soils from gravity action. Subsoil and water table drains provide an important component in all types of pavements including those stabilised.
A stabilised subgrade reduces or eliminates the migration of soil particles into the overlying aggregate which can cause aggregate contamination and act as a lubricant between the aggregate particles leading to pavement failure. A stabilised subgrade will prevent this and also stop aggregate particles from punching into the subgrade and the subsequent loss of pavement integrity.
Other Benefits of Stabilised Subgrades:
- Reduces the risk of costly subgrade pavement failures.
- Creates a more uniform pavement layer.
- Reduces the soils moisture content and increases its workability.
- Eliminates or reduces the necessity for undercutting and the associated cost and environmental impact that transportation and disposal of unsuitable material involves.
- Reduces construction time.
- Is a proven, cost effective and durable pavement component.
- Reduces transport demands on existing roading infrastructure by reducing aggregate and "undercutting-to-waste" requirements.
- Provides a superior working platform especially during winter construction.
Subgrade stabilisation should always be the first factor considered when designing a new pavement. If not designed for, subgrade stabilisation should be considered at the construction phase, which is often the case, as the benefits are numerous, the potential savings in time and cost are significant and a superior pavement will be constructed.
Hiway Stabilizers have the experience and expertise to undertake all types of subgrade stabilisation. Our stabilisation plant inventory is second to none and is operated by highly skilled and efficient crews capable of high production outputs while maintaining the highest quality standards.
We service locations all throughout Australia and New Zealand, including New South Wales, Queensland, Victoria, South Australia, and Tasmania.