Abstract
Bound water is an important factor in controlling the physical, chemical and mechanical properties of clayey soils, and it plays an important role in geotechnical engineering disaster prevention and environmental protection. There are many factors (such as soil texture, mineral composition, specific surface area (SSA), organic matter content, porosity and so on) that affect bound water in natural clayey soils. However, the main factors are mineral composition and specific surface area (SSA). Experimental tests on specific surface area and isothermal adsorption of a series of artificial mixed clayey soils were carried out to determine the different types of bound water. On this basis, the relationship between the bound water of mixed clayey soils and influencing factors of mineral composition and specific surface area are discussed. The results show that relative humidities of RH = 0.90 and 0.98, in an isothermal adsorption method, are the boundary-dividing points between strongly bound water and weakly bound water, and between weakly bound water and free water, respectively. The bound water content of the mixed clayey soils increased linearly with the montmorillonite content and specific surface area. Clay’s mineral composition (montmorillonite) was found to be the most fundamental influencing factor.
Highlights
Clay minerals are the main components of clayey soil, which adsorb bound water because of their hydration-activation centers
In equation: SSA is specific surface area (m2 /g); CMB is methylene blue concentration (g/mL); V is the volume of methylene blue solution adsorbed; NA is the Avogadro constant, which equals to 6.02 × 1023 mol−1 ; AMB is the area covered by one MB molecule, which equals 130 Å2 ; ms is the quality of dried soil sample; 319.87 is the molar mass of the
ΩMnt+Kln = mMnt · ωMnt + mKln · ωKln ωMnt+Fsp = mMnt · ωMnt + mFsp · ωFsp where: ωMnt+Kln, ωMnt+Fsp are the amounts of superimposed adsorption bound water of mixed clayey soils at a given relative humidity (RH), respectively; ωMnt, ωKln, ωFsp are the amounts of adsorbed bound water of montmorillonite, kaolin and feldspar at a certain relative humidity (RH), respectively; mMnt, mKln, mFsp are the percentages of montmorillonite, kaolin and feldspar in the mixed soils, respectively
Summary
Clay minerals are the main components of clayey soil, which adsorb bound water because of their hydration-activation centers. The quantified boundaries help to predict the physical–chemical processes that occur after clay minerals are combined with water, and control the special physical, chemical, and mechanical properties of hydrated clay It plays an important role in geotechnical engineering disaster prevention and environmental protection [8,9]. This study carried out isothermal adsorption tests on a series of artificially mixed clays and found the types of bound water adsorbed by clayey soils and their boundaries. On this basis, the relationship between the combined waters of mixed clayey soils and influencing factors, such as mineral composition and specific surface area, are discussed
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