Proewater chemistry in compacted bentonite

摘要

The porewater chemistry in compacted bentonitewas studied in solution-bentonite interaction experiments. Theparameters varied in the experiments were the bentonite density,bentonite-to-water ratio (B/W), ionic strength of the solution,and the composition of bentonite. The bentonite types used in theexperiments were Volclay MX80 and artificial bentonitesprepared from purified MX-80 in sodium form where CaCO3andCaSO4 were added. At the end of the experiment, theequilibrating external solution and the porewater squeezed outthe bentonite ware analyzed to give information for interpretationof the interaction. The equilibrium was modelled with the HYDRAQL code.The evolution of porewater chemistry was determined by thedissolving components initially present in the bentonite togetherwith the ions entering with water from the surroundings. Ion-exchange processes occurred between the bentonite and theporewater. The concentrations in the external solution andporewater strongly depended on the B/W used. Theconcentrations in the squeezed porwaters were clearly lower thanin the equilibrating waters. The modelling results reasonably fitthe experimental data.