Untersuchungen zum Quellpotenzial von Bentoniten unter dem Einfluss von Biostimulation

Investigations on the swelling potential of bentonites influenced by biostimulation.

This contribution addresses the influence of microbiological accumulation on swelling behaviour of bentonites. Therefore, materials composed of 30 % bentonite and 70 % natural silt have been treated with C6H12O6 acting as an energy as well as carbon source in order to initiate microbiological growth of the present population (biostimulation). Two bentonites have been investigated differing in terms of their interlayer cations: Calcigel primarily exhibiting Ca++ cations and MX 80 primarily exhibiting Na+ cations within the interlayer space. Due to this compositional difference Calcigel swelling is significantly determined by processes of innercrystalline swelling, whereas MX 80 bentonite exhibits distinctive osmotic swelling. It was found that metabolic processes leading to gas generation within the samples have a great influence on volume change of Calcigel mixtures, whereas water adsorption of the same samples was rarely affected. On the other hand, samples of MX 80 mixtures exhibit a significant decrease in osmotic swelling. During the swelling tests the pH value in the pore fluids of both, accumulated Calcigel- and MX 80-samples decreased from 7,4 to 4,8. This change in environmental conditions accounts for the decrease in the sensitive process of osmotic swelling.