What is Soil Stabilisation?

Quite simply it is the method used to change an unsuitable material into one that can be used for a range of applications. This can be from an engineered fill to a Cement Bound Granular Material (CBGM) sub-base replacement. Most soils in the UK can be used for one form of soil stabilisation or another by using dry binders .


The two main dry powders used are Quicklime (CaO) and Ordinary Portland Cement (OPC). In soils with a high sulphate content Ground Granulated Blast Furnace Slag (GGBS) is preferred.

Quicklime is predominantly used in clay and silty soils for stabilisation purposes.  It is a very useful drying-out agent in sandy and gravelly materials as it reacts aggressively with moisture. Added to clay/silt the CaO reacts with the film of moisture that is present around each particle. This reduction in liquid allows the particles to be compacted together tighter than before, typically achieving 5% air voids or less. In addition to this there is an increase in the CBR and the plastic limit of the material almost immediately. After the initial application pozzolanic (cementing) reactions take place. These result in further increases of CBRs, greater frost resistance, improved stability against swell and shrinkage. In addition, also higher levels of shear and tensile strength.

The addition of cement to lime treated clays will result in even higher CBRs and provide a non-frost susceptible material (subject to laboratory testing to prove this). More importantly, it is used as a binder when stabilising granular or sandy materials

In addition Pulverised Fuel Ash (PFA) can be used to provide ‘bulking up in materials that have little, or no natural binding ability of their own. The PFA also has natural cementitious values. These also help to improve the strength of the material that has been treated.

In recent years, there has been an increase in the use of hydraulic binders made from recycled cementitious products and other binding agents. These products offer a wider range of treatments to materials. Beach management have had successfully use these binders in many projects.


The key to stabilisation, however, is the testing of materials before, during and after application. This ensures that the specifications for the contract are achieved. With this and a good working practice, stabilisation is one of the most economic and environmentally friendly construction practices in use.


Our service can quickly give you a capping equivalent 15% CBR using site soil.


By adding a higher level of powder we can achieve a sub-base equivalent CBR of 30%.


We can insitu stabilise formations at up to 350mm which reduces the amount of excavation, disposal and placement.