Effect of Inorganic Salt Solutions on the Consistency Limits of Two Clays

Due to its low permeability, a clay liner is the main material used in solid waste disposal landfills. It is exposed there to various chemical, biological, and physical events, and the clay liner is affected by the resulting leachate. For this reason, when attempting to define the geotechnical characteristics of clay liners, the use of distilled water or tap water is far from being representative of the in-situ conditions. In this study, the effects of 4 different salt solutions on the consistency limits of clays were experimentally investigated. The salt solutions used as leachate compounds were ammonium chloride (NH4Cl), potassium chloride (KCl), copper(II) sulfate (CuSO4), and iron(II) sulfate (FeSO4). Consistency limit tests were conducted on low plasticity (CL-class) and high plasticity (CH-class) commercial clays using both distilled water and these salt solutions. The experimental results indicated that the liquid limit increased when the salt concentration for the CL clay was increased. Moreover, the liquid limit was found to decrease when the salt concentration for the CH clay was increased. The plastic limit of the CL clay increased as the salt concentration increased to a certain value. However, the plastic limit of CH clay decreased at low salt concentrations and increased at high salt concentrations. In addition, the test results indicated that salt solutions at high concentrations changed the soil class of clays. In other words, for the conditions investigated, CL and CH class clays were transformed into low plasticity silt (ML) and high plasticity silt (MH) class soils, respectively, according to the Unified Soil Classification System (USCS).