Durability studies on stabilization effectiveness of soils containing different fractions of montmorillonite

Stabilization of clays with additives such as lime and cement has been practiced for several years and worked well in improving the subgrades. The stabilizer design based on PI and gradation of the soil was widely followed. Though this practice is used widely, there were cases where the treated subgrades exhibited premature failures. Many cases were reported, where the treated subgrade experienced failures due to loss of stabilizer over a time period, or a stabilizer being ineffective in certain soils. The design methods need to be examined by incorporating clay mineralogy and durability of the treatment studies.;An experimental study was conducted here on four soils having different mineralogical characteristics. The soils were studied with two types of stabilizers (lime and cement). The first task is to assess the long term durability of stabilized expansive clays with distinct clay mineralogy by subjecting them to wetting/drying studies. This study replicates moisture fluctuations occurring during seasonal variations. Volumetric strain and unconfined compressive strength of the soil specimens were monitored at select cycles during wetting/drying cycles. The second task is to study the soil specimens under severe rainfall conditions which can be replicated in the lab with the help of Leachate apparatus. Leachate coming out from the soil specimens was studied for calcium concentrations and pH variations during select cycles. Also the final strength retained in the soil specimen is found after leaching for 14 cycles. Calcium concentrations, pH and cation exchange capacities of soil specimens at select cycles were monitored.;Durability test results were analyzed to understand the importance of mineral Montmorillonite in clays on their stabilization process. Results revealed that there is considerable effect of mineral Montmorillonite on the stabilization effectiveness of clays where an increase in the percent amounts of this mineral resulted in the poor performance of stabilized soils during durability studies. Leaching of stabilizer was small and hence did not influence the treated soil strength. This research paves way for future research studies to increase the accuracy of selecting a stabilizer by the inclusion of clay mineralogy and durability aspects in the stabilizer design methods.