Bentonites as a basic material for technical base liners and site encapsulation cut-off walls

Abstract Bentonites and bentonite containing sealing materials are used for many years for sealing purposes in foundation, dike construction, hydraulic engineering and landfill construction, especially for encapsulation of old waste deposits. Because of their exceptional physical, structural and chemical properties, bentonites are offering manifold possibilities to protect the environment against the negative effects of dumping grounds. Often the observance of legal regulations for waste dumping or for the encapsulation of contaminated areas is possible only by using bentonite containing sealing systems. The different techniques of making horizontal technical base liners and vertical cut-off walls are illustrated as well as the essential properties of the bentonite with respect to the bentonite containing building materials. For horizontal technical base liners the adsorption ability, the ion exchange capacity and the swelling behavior of bentonite is important. For cut-off walls bentonite controls the rheological behavior of the slurry and is responsible for the low permeability of the hardened bentonite-cement-wall. The composition and properties of mineral sealing mixtures are illustrated by examples of usage as well as the application in the building practice. Results of recent developments for improving the material properties of bentonite containing mineral sealing mixtures, e.g. ready mixtures of bentonite/cement, are presented followed by a conclusive outlook to the further possible developments.