Swelling–shrinkage kinetics of MX80 bentonite

Abstract

The swelling–shrinkage kinetic of an industrial Bentonite (MX80) was investigated using a new technique of environmental scanning electron microscopy (ESEM) coupled with a digital image analysis (DIA) program (Visilog). This expansive clay was characterized by several analytic tools (ICP-AES, SEM, STEM, XRD, etc.), before applying the new ESEM technique. The swelling–shrinkage was directly observed at high magnification and at different relative humidity states in an ESEM. Nine wetting/drying cycles were performed on the sample. Each cycle was performed at different relative humidities (55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95%). A DIA program was used to determine swelling–shrinkage. This method consists of estimating the percent augmentation of the surface as a function of time. Finally, a swelling–shrinkage kinetic model was tested, based on a first-order linear kinetic equation. The results show that the coupled ESEM and DIA can be a powerful method of estimating the swelling/shrinkage potential of expansive clays. The exponential model fits well with the experimental data.