Abstract
This work presents a method to determine the plasticity of clay soils using Fourier transform mid-infrared (FT-MIR) spectroscopy. Samples of mono- and polymineral soils of varying water contents are studied. The FT-MIR results are compared with the results obtained from standard Russian and international methods for the plasticity range. The correlation between the consistency of clay soils, when displaying their plastic properties, and the position of the Si–O stretching band in the FT-MIR spectra is established. The possibility of, and interest in, determining the plasticity characteristics of clay soils using mid-infrared spectroscopy is demonstrated: it yields effectively higher precision results compared to standard test methods. It is shown that the method of IR spectroscopy allows the fixing of the start and the completion of the series of “phase transitions” of the soil in the plastic and liquid state. The significant effect of the concentration of non-clay minerals on the Si–O ν line is that a moisture content curve is noticed, which may help to predict the clay content of the soil without undertaking XRD analysis.
Highlights
Plasticity is one of the key indicators most widely used in the classification of clay soils and in determining their properties [1]
In engineering and geological studies, it is a common practice to use as plasticity indicators the values of water content that correspond to the transition of soils from the solid state to the plastic state and from the plastic state to the liquid state
This paper considers the possibility of the application of mid-infrared spectroscopy for revealing the mechanism of plasticity formation and determining the criteria of structural phase transition of soils into solid, plastic and fluid states
Summary
Plasticity is one of the key indicators most widely used in the classification of clay soils and in determining their properties [1]. This characteristic largely determines many technological processes of constructing geotechnical structures as well as the manufacture of ceramic products [2]. The interval of moisture content between the plastic and liquid limits gives the plasticity index (PI), which is used as an indicator in soil classification. The plasticity characteristics are used to analyze the engineering and geological conditions of the construction site with conclusions about the suitability of soils composing the compressible thickness at the base of the foundations. Low-plastic clays are poorly formed, and clays crack during drying and require the use of lean additives [2]
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