title: Swelling-shrinkage measurements of bentonite using coupled environmental scanning electron microscopy and digital image analysis.
abstract: The swelling clays have been proposed as engineered barriers in geological disposal systems for waste because these materials are assumed to build a better impermeable zone around wastes by swelling. However, the swelling potential of soils is also considered a prevalent cause of damage to buildings and constructions. For these reasons, it is fundamental to investigate the physicochemical and mechanical behavior of swelling clays. In the current study, the swelling-shrinkage potential (aggregates scale) was estimated using an environmental scanning electron microscope (ESEM) coupled with a digital image analysis (DIA) program (Visilog). In fact, the isolated aggregates of raw and cation-exchanged bentonite were directly observed at different relative humidities in an ESEM chamber. Then the "Visilog" software was used to estimate the percent augmentation of the aggregate surface as a function of time and as a function of relative humidity. This estimation allows for the calculation of the swelling-shrinkage potential (%) of bentonite. Finally, a kinetic model of first order was tested to fit the kinetic experimental data of swelling-shrinkage potential. The results show that ESEM-DIA coupling can be a powerful method of estimating the swelling-shrinkage potential of expansive clays. In addition, the exponential models fit well with the kinetic experimental data.
authors.affiliation: UMR 7517 ULP--CNRS, CGS, 1 rue Blessig, F-67084 Strasbourg, France. montes@illite.u-strasbg.fr
authors.forename: G
authors.initials: G
authors.lastname: Montes-H