Characterization of kaolinitic clays subjected to alkali contamination

Differential settlements due to alkali contamination in the foundation soil and the deformations in superstructures were well documented. The influence of alkalis on clay minerals has been the subject of many studies for decades. However, studies on the role of mineral content, type of alkali and volume of the interacting solution on the dissolution of clay minerals and formation of new minerals at hydrothermal condition are scanty for a particular duration and concentration of alkali. Thus, in this paper micro level investigations were carried out to clearly understand the influence of alkalis with the varying volume of interaction on the new mineral formation along with the dissolution of the actual mineral. Two soils, namely, natural red earth and commercial kaolin with varying kaolinite content were selected for this study. The mineralogical and the morphological aspects involved in alkali treatment of these soils have been investigated using XRD, SEM, FTIR, and TG-DTA. The results showed that both red earth and kaolin treated with alkali solutions (4N NaOH and 4N KOH) at 110 degrees C showed the complete dissolution of mineral at higher volume of interaction. However, at given thermal condition, complete dissolution of mineral in red earth occurred at a lesser volume of interaction compared to kaolin. Furthermore, the dissolution of the original mineral and the intensity of new mineral formations varied with mineral content, volume of interacting solution and the type of alkali. Thus, the detailed analysis of the results clearly brought out that the disintegration of the actual mineral and the formation of new minerals greatly depend on the mineral content and volume of interaction