Soil Stabilisation (or Lime Treatment of Soils)
Soil stabilisation by Lime Treatment can be achieved by applying a controlled dose of quicklime, hydrated lime or liquid lime to soil.
Cohesive soils can be stabilised using quicklime or hydrated lime but only quicklime causes drying
of the soil. This process enables unacceptably wet or cohesive materials to be treated and used for
construction purposes. Different treatments are available to suit virtually every soil type and can
produce a range of different strengths according to use.
Lime Improvement is a quick and simple operation that can be incorporated into any earthmoving
contract no matter how large or small. Because the nature of the soil is quickly changed to improve
the handling characteristics, productivity is often enhanced. The segregation of unacceptable
material is also eliminated. This is simply treated with lime as it is identified to obtain the soil
properties that are required.
One of the great advantages of improving soils with quicklime is the ability to retain all material on
site. This eliminates the need to remove material to tip and saves the cost of tipping and haulage
charges. This often has an impact on the construction programme as it is usually considerably
quicker to treat soils on site rather than dig, dump and replace.
The mechanisms of Lime Treatment of Soils
- Improvement (quicklime addition only)
Once quicklime is mixed with the moisture bearing soil an exothermic (heat producing)
reaction takes place.
||1,140 kJ/kg CaO
In a homogeneous mixture, the quicklime reacts with the moisture present in the
soil. This exothermic reaction generates significant amounts of heat energy which will dry the soil
(temperatures can reach in excess of 100ºC) as well as chemically binding 32% of it’s own weight
of water as hydroxide.
2. Modification (quicklime or hydrated lime / liquid lime addition)
The next steps, Modification and Stabilisation only occur with clay soils. When quicklime or
hydrated lime is added to a clay soil, the clay platelets go through an ion exchange process, which
introduces calcium into the clay surface and causes a change in the way the clay platelets align, as
shown in the pictures below. This gives an increase in soil strength and will normally occur quite
rapidly (usually within two hours of mixing but can take up to a day depending on site conditions).
3. Stabilisation (quicklime or hydrated lime / liquid lime addition)
The silica and alumina contents of the clay soil will react with the calcium present in the lime to
form calcium silicate hydrates or calcium aluminate hydrates. This reaction is slow to proceed and
is similar to the reactions that occur when cement cures. The strength gain can continue for over
The process is simple and can range from basic plough and disc harrow through to purpose built
lime spreaders and rotovator. This allows lime treatment work to be carried out from small to major
Contact the British Lime Association members who have extensive experience of Lime Treatment of Soils and are available to help with your project.
Advantages of Lime Treatment
- Save ££££'s - Reduce Project Costs.
- Save Time - Bring your project back on schedule or even finish early !
- Least Environmental Impact - Minimise vehicle movements and disturbance to the
- surrounding areas.
- Minimise - Waste generation, tipping and aggregate fill demand.
- Avoid - Aggregate and Landfill Taxes.
- Simple - process and equipment requirements.
- Long History of Use - Used widely for many years throughout the World.
Lime Treatment of unsuitable or contaminated soil is a simple process which is being used to
strengthen, dry out or remediate unsuitable ground. There is a long history of use on large and
small projects alike.
Main Contractors are saving considerable amounts of time and money by using Lime Treatment,
which avoids the need for dig and dump by treating material in situ. This reduces imported
aggregate and landfill costs and can often be done with simple, readily available equipment either by an earthworks contractor or a specialist subcontractor.