A simplified method for determining the external specific surface area of non-swelling fine-grained soils

The physical and mechanical properties of fine-grained soils, especially clay minerals, are greatly influenced by the specific surface area. Many investigations were conducted to examine the relationships between the specific surface area of soils and their engineering properties. We have previously shown that there were relationships between the external specific surface area of the soils and their Atterberg limits. These relationships, based on the test results from soils prepared artificially in the laboratory, were presented in a general analytical form. As Atterberg limits are the most distinctive and the easiest property of soils to measure, it would be a very convenient basis for estimating the specific surface area. The aim of these investigations was to identify the possibility of practical applications. Five heterogeneous soil samples were selected, the liquid and plastic limits were measured as well as the grain size distribution, the mineral and chemical compositions and the specific surface area. The external specific surface area of the soils measured by the BET method ranged between 17 m2/g and 54 m2/g. The estimated values using Atterberg limits were slightly higher. The calculated and measured values of the external specific surface area differed by 0.6–6 m2/g.