Abstract: “Specific surface area (SSA) is one of the engineering properties of clayey soils. This property is highly related to the particle size, strength, compressibility, and permeability of soils. Particle size (i.e., clay fraction) is the most important physical property of clay minerals. Liquid limit (LL), as one of Atterberg’s limit, is also an important index to classify fine-grained soils. Kaolinite (non-expansive soils) and calcium bentonite (expansive soils) are selected as primer soils, and 0% to 40% sand is added to each soil to reduce clay fraction. These ten representative samples are then tested using the BET method to determine the SSA. The SSA of ten compounded samples of kaolinite and calcium bentonite are in the range of 16.2 m2/g–18.8 m2/g and 58 m2/g–69 m2/g, respectively. Results also show that the increase in clay fraction is accompanied by an increase in the SSA of both kaolin and bentonite. The increase in LL is also accompanied by an increase in SSA. The empirical corre”

Keywords: BET, clay, calcium bentonite, kaolin, specific surface area, permeability