Effect of Alkali Concentration on Swelling Characteristics of Transformed Kaolinitic Clays
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EFFECT OF ALKALI CONCENTRATION ON SWELLING CHARACTERISTICS OF TRANSFORMED KAOLINITIC CLAYS P. L. SRUTHI AND P. H. P. REDDY * 1
National Institute of Technology Warangal, Warangal 506004, India
Abstract—Soil–alkali interaction leads to abnormal soil behavior due to significant changes in mineralogy and morphology. The effect of alkali on the swelling behavior of natural clays has been explored in recent years, but the swelling behavior of alkali-transformed clay minerals is still unclear. The objective of the current study was to investigate the effect of alkali concentration on swelling characteristics of natural and alkali-transformed kaolinitic clays. The study was complemented further with micro-level investigations. Red earth and kaolin, which are regarded as non-swelling kaolinitic clays, were utilized. The results showed that alkalis induced greater swelling in natural clays than in alkali-transformed clays. The results revealed further that alkali-transformed clays exhibited decreases in swelling when exposed to increased alkali concentrations. Moreover, the degree of transformation played an important role in the swelling behavior of alkali-transformed kaolinitic clays when inundated with water and with various alkali concentrations. These variations may be attributed to the different extents of mineralogical and microstructural changes caused by alkali treatment. Keywords—Alkali . Kaolinite . Micro-level investigation . Swelling . Transformed Clay
INTRODUCTION In modern environments, soil in natural or modified forms has been used increasingly for various civil engineering activities. Directly or indirectly, the effects of modernization and the depletion of natural resources have affected soils adversely due to various anthropogenic activities, including contamination by accidental spills or leakages of industrial effluents (acids, alkalis, etc.), petroleum, heavy metals, and pesticides (Wang 2003; Onojake and Frank 2013). Among the many sources for soil contamination, alkalis are released, for example, from paper, paint, dye, pulp, and aluminum industries and cotton mills. Alkali contamination has led to soil structural failures due to the formation of neogenic hydrated salts (Sokolovich and Troitskii 1976; Kabanov et al. 1977; Shekhtman et al. 1995). Much research has been conducted to understand the mineral alterations produced by soil/alkali interactions (Cuadros and Linares 1996; Taubald et al. 2000; Wang and Siu 2006a, 2006b; Elert et al. 2008; Jiang et al. 2008; Alshaaer 2013; Elert et al. 2015; Boussen et al. 2015). Continuous wetting of soils by alkalis and exposure of rock-forming minerals to alkaline solutions can lead to neogenic zeolite formation, with the type of zeolite produced depending heavily on the origin, duration of reaction, temperature, and chemistry of the pore fluids. Batch reactor experiments were conducted (Chermak 1992) to understand changes in the mineralogy of the Opalinus shale due to the influence of highly concentrated NaOH solutions. The general sequence of reaction pr
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