Durability Studies On Stabilization Effectiveness Of Soils Containing Different Fractions Of Montmorillonite

Abstract

Stabilization of clays with additives like lime and cement has been practiced for several years and worked well in improving the subgrades. Though this practice is used widely, there were cases where the treated subgrades exhibited premature failures. Many departments of transportation (DOT) agencies in the United States have had subgrade failures even after stabilization with chemical additives due to loss of stabilizer over a time period, or a stabilizer being ineffective in some soils. The design based on PI and gradation of soil followed by many DOTs is quite misleading due to the lack of inclusion of basic soil properties such as mineralogy in the design. An experimental study was conducted on four soil specimens having different mineralogical characteristics. The soil samples were studied with two types of stabilizers (lime and cement). The first task is to assess the long term durability of stabilized expansive clays by subjecting them to wetting/drying studies which replicate moisture fluctuations occurring during seasonal variations. Volumetric strain of the soil samples and unconfined compressive strength were monitored at select cycles. The second task is to study the soil samples under severe rainfall conditions which can be replicated in the lab with the help of Leachate apparatus. Leach coming out from the soil samples was studied for calcium concentrations and pH during select cycles. Also the residual strength retained in the soil specimen after leaching for 14 cycles is monitored. Test results were analyzed to find out a way of correlating the importance of mineral Montmorillonite in stabilization process. This research paves way for future researchers to increase the accuracy of selecting a stabilizer by the inclusion of mineralogy in the design charts.