Impact of Initial Hydration of Bentonite on Its Plasticity Properties Change in Interaction with Organic Contaminant

The compacted clay liners (CCLs) due to their low permeability and suitable capability for contaminant retention are widely used in engineering waste disposal sites. Generally, the change in properties of soil pore fluid has a very distinguished impact on the behaviour of clayey soils. In spite of several researches, which have been performed on the process of clay and organic contaminant interaction, there are few researches on the influence of dielectric constant of organic contaminant and initial hydration of bentonite on the geotechnical and geo-environmental properties of organic contaminated bentonite. Such a process is very common in many industrial and waste disposal projects.

This research was performed on sodium-bentonite soil samples which were exposed to two different organic materials (Ethanol and Acetic Acid) which have different dielectric constant. Furthermore, two different pre-hydration and post-hydration conditions were studied in this research. After achieving equilibrium condition, the influence of initial hydration and change on the dielectric constant of pore fluid upon interaction of organic material and bentonite was investigated. The investigation focuses attention on the plasticity properties of bentonite by the use of Atterberg limit tests.

The achieved results indicate that in Casagrande's plasticity chart, two pre-hydrated sodium-bentonite soil samples which were exposed further to ethanol and acetic acid are classified as CH and shifted from CH to MH, respectively.

 Discussion and Conclusion:

The change on the dielectric constant of pore fluid and different hydration conditions cause a change on the thickness of the double layer of clay fraction of the soil. This causes a noticeable change on the structure and behaviour of clay fraction of the soil sample. This variation on bentonite behaviour has been discussed based on the current available theory of double layer. Furthermore, the theoretical limitation for interpretation of results has been addressed.