Admixtures and in-situ soil mixing

Admixtures are used to stabilise soils in the field, particularly fine-grained soils. The most common admixtures are lime, cement and fly ash. The main purpose of soil stabilisation is to  

The improvement is based on in-situ mixing of soil with admixtures, which chemically react with the soil and/or the groundwater. Generally the resulting stabilised soil mass has a higher strength, lower permeability and lower compressibility than the native soil. For environmental treatment, admixtures can be enriched with chemical oxidation agents or other reactive materials to immobilise or neutralise contaminants (Moseley et al, 2004). 

The most important techniques to create stabilised columns or walls in the soil are in-situ Deep Soil mixing Methods (DSM) and shallow mixing methods (SSM). Both methods are based on the construction of stiff columns in soft ground. These columns consist of a mixture of the natural soil with stabilizing additives which are added as dry or wet components and mechanically mixed with the soil (Moseley et al, 2004). 

Strength improvement can be determined from pre- and post-treatment CPTs or laboratory tests on undisturbed samples. Proper care should be given to the selection of the stabilising material  

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