Abstract
Problem statement: The characterization of smectitic clays has been traditionally made using physical and chemical methods which are time-consuming and require costly equipment. Adsorption of methylene blue by these clays has been introduced as a quick and cheap method for the estimation of cation exchange capacity and surface area. Therefore, the aim of the present study was to test the applicability of the methylene blue method for the determination of cation exchange capacity and specific surface area of Egyptian smectitic clay deposits and hence to estimate their content of expansive clays. Approach: The distribution of sand, silt and clay fractions was determined in the studied samples by grain size analysis. The methylene blue test was applied using the halo method for the determination of the optimum adsorption point. Results: A positive correlation was found between the cation exchange capacity of the claystone as determined by the methylene blue value and its clay fraction and between the specific surface area and the cation exchange capacity. Conclusion/Recommendations: It has been concluded that the methylene blue test can be used as a reliable and rapid method for the characterization of smectitic clay deposits and soils containing smectite. These properties are important for engineering and environmental geological assessments of sites for different construction purposes.
Highlights
Smectitic clay deposits of Upper Eocene and later geological ages occur in several localities in Egypt
The aim of the present work was to study the application of the methylene blue method as a tool for the characterization of Egyptian smectitic clay deposits
The deviation from a perfect correlation and the scatter of some points are due to the variation of the clay content in the claystone samples and due to the variation of the smectite content in the clay fractions
Summary
Smectitic clay deposits of Upper Eocene and later geological ages occur in several localities in Egypt. The geology and mineralogy of these deposits have been described by several authors, for example by Attia (1996). These authors used X-ray diffraction and/or Fourier Transform Infrared for determining the composition of clay minerals present and chemical methods for the determination of cation exchange capacity of the clays. Such techniques are time-consuming and quite costly. Hitherto, been made to use the much simpler methylene blue method to characterize these clay deposits
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