Tuesday 4 September 2012

Soil Stabilizers

I would like to make some points to try to explain ionic soil stabilizers. 

Soil stabilizer is not the correct term, but it is the one commonly used.  Compaction aid or soil consolidation aid are the more correct descriptive words, but the soil is modified and performance is much more stable in high clay soils – so the term stabilizer does apply.

In order to be able to conduct some performance testing on treated soil, one needs to understand the way in which the product reacts with the soil.  Clays contain certain cations with an ionic imbalance, and in nature the way this ionic imbalance is satisfied by water.  These cations attract and “hold on to” a large number of water molecules, called adsorbed water, which surround the clay particle and these water molecules can only be removed by high pressure or temperature e.g. in a potters kiln.  The fact that you try to compact water coated molecules reduces particle interlock and so reduces strength, this is usually referred to as plasticity.

The ionic stabilizer exchanges these cations in the clay with ones that are in ionic balance and the adsorbed water that was previously held onto by the clay is now released and has to make its way up to the surface of the treated layer to evaporate from there. This water release takes time and depending upon the soil type, traffic and weather conditions can take up to 30 days.  During this time, the treated layer becomes more dense as well as drying out and so increases in strength. Depending upon the product used the soil will not re-adsorb the water as it has previously and therefore exhibit higher strength even in wet weather.  In essence the effect is one of the reduction in susceptibility to moisture of clay based roads.

The treatment is non cementitious like lime or cement or other methods like polymers. So the soil will achieve it natural strength rather that that provided by the above methods.

In testing the effects of this treatment, one has to prepare two sets of samples, one treated and one untreated.  Both samples have to be let to dry out for 10 to 20 days and then tested and a significant improvement in the treated samples will be noted over the untreated samples. 

By: Rhino Rohrs

www.cbrplus.com / www.gravelock.com