Swelling and mineralogical characteristics of alkali-transformed kaolinitic clays

Abstract

This work investigates the swelling and mineralogical characteristics of alkali-transformed (partially and completely transformed) kaolinitic clays to bring out the subsequent effect of alkali contamination. One-dimensional free swell tests were conducted to determine the degree of swelling on alkali-transformed kaolinitic clays inundated with water and 4 N NaOH. Swelling increased in transformed clays with an increase in degree of transformation when inundated with water. An opposite trend was observed in the swelling patterns of alkali-transformed clays upon inundation with 4 N NaOH when compared with water i.e., swelling decreased with increase in degree of transformation upon inundation with 4 N NaOH. This was mainly attributed to mineralogical changes, which occurred in transformed clays. This was confirmed by X-ray diffraction (XRD) analysis. To further re-confirm the changes observed, Fourier transform infrared spectroscopy (FTIR), and Thermogravimetric-Differential thermal analysis (TG-DTA) techniques were carried out. Complete kaolinite mineral dissolution and neogenic formations (mainly sodalites) were the key factors for differences in swelling tendencies when inundated with water or 4 N NaOH.