Property Changes in Lime Treated Expansive Clays under Continuous Leaching

This report is the result of a study to determine what effects continuous water leaching has on the engineering, physical, and chemical properties of three lime treated expansive clays in north central Texas. Seventy laboratory prepared lime treated clay samples were subjected to continuous accelerated leaching for 45 and 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 soils 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 properties. Chemical properties measured were soil pH, pore-water 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 a detrimental impact on the properties of lime treated expansive clay.