Specific Surface Area of Plastic Clays from Equilibrium Sediment Volume under Salt Environment

Abstract

Abstract Specific surface area is one of the crucial surface properties of clay soils. The surface area is used as the surrogate compatibility index and is related to many engineering properties of clays. Accurate estimation of the surface area, Sa, is essential for predicting the saturated and unsaturated characteristics of clays in engineering applications. A simple technique for a routine estimation of the surface area of plastic clays was developed based on the sediment volume in the salt environment. The method utilized equilibrium sediment volume measurement of clay soil in 0.1 N sodium chloride solution and used the theoretical equation for the surface area estimation, which accounts for both the surface and body forces. A comparative assessment of the proposed method with commonly used techniques on 12 clay soils is presented. The proposed method showed a good agreement, qualitatively, with the ethylene glycol monoethyl ether (EGME) and methylene blue methods for the studied soils. The estimated surface area by the proposed method was, however, higher than the existing two methods for the highly plastic clays, such as the bentonites. The relative merits of different methods are discussed in detail. The utilization of water as the probe molecule in the proposed method in a dispersed state of the swollen clay structure ensured greater accessibility to the internal surface. The proposed method was a quick and simple way to estimate the specific surface area of soil with great repeatability. The method is beneficial for routine practice to estimate the surface area of soils and should be readily adopted in the standard practice as an additional method.