| This report is the result of a study to determine what effects continuous water leaching has on the engineering, physical and chemical properties of lime treated expansive clays in north central Texas. Seventy laboratory prepared lime treated clay samples were subjected to continuous accelerated leaching for 45 to 90 days in large diameter, flexible wall leach cylinders. Constants during the leach testing were types of soil used, flow pressure, curing conditions, and compaction effort. Variables were lime content, initial moisture content, and duration of the leach cycle.; The soil's physical and chemical properties were measured before and after leaching then graphically and statistically compared. Physical properties tested included permeability, Atterberg limits, linear shrinkage, swell properties, unconfined compression strength, and differential thermal analysis (DTA) properties. Chemical properties measured were soil pH, porewater cation extractions and exchange complex cation extractions. Extractions were tested for calcium, sodium, magnesium and potassium cations. Additionally, the leachate passing through the soil was collected and monitored for changes in pH and cation concentrations.; Results indicate that leaching does have detrimental impact on the properties of lime treated expansive clay. The changes in the soil's physical and chemical properties are related to lime content and moisture content during compaction. The permeability of all samples tested increased dramatically with the addition of lime, and it is speculated that permeability plays a key function in determining the amount of physical and chemical change that occurs during leaching. Maximum detrimental changes generally occurred at lime contents at or less than the lime modification optimum (LMO). At lime contents at or above the lime stabilization optimum (LSO), the detrimental effects were minimized.; An estimation technique to correlate laboratory leach results to field predictions of calcium removal and soil pH declination is presented. Field samples of known lime specifications were used to validate the technique with limited success. |
