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Physico-chemical characterization of alkali-contaminated tropical kaolinitic clays

ABSTRACT This paper presents results of a laboratory investigation aimed at evaluating the influence of alkali on physico-chemical characteristics of kaolinitic clays. A series of experiments, atterberg limits, free swell index, specific gravity, cation exchange capacity, specific surface area, X-ray diffraction, scanning electron microscopy and Oedometer free swell test, were performed on two tropical kaolinitic clays. Based on the results, it was found that the amount of kaolinite mineral in clay significantly influences its behaviour . Once alkali attacked nucleus of clay mineral, the behaviour of clay was governed by the formation of sodium or potassium aluminosilicate complex (zeolite minerals), as evidenced by mineralogical and morphological studies. Swelling results on typical samples clearly illustrated that the plasticity properties could not be a true indication of swelling behaviour of alkali-contaminated clays unlike natural clays. Overall, mineralogical, chemical and physical analysis showed that the behaviour of alkali-contaminated clays cannot be elucidated without multi-phase characterization techniques.