Cesium and strontium partitioning during hydration of calcium aluminosilicates

By extracting and analyzing the pore solutions of a series of blended cement pastes as a function of time it was determined that cesium and strontium were being incorporated by various hydrated solid phases and that the incorporation was in some cases still in progress after 28 days of curing. Comparison of the pore solution and leachate data indicated that a direct relationship between the two does exist and that the pore expression technique may prove valuable in predicting possible leaching behavior of cement-based waste forms.;Although the analysis of the pore solution did provide important partitioning data, it did not provide information concerning which phase or phases were incorporating cesium. Therefore, experiments were performed in which a series of calcium aluminosilicate glasses were hydrated with CsOH solution, CsCl solution and deionized water at 38 and 90;The correlation between pore solution and leachate data led to the development of a conceptual model in which the early leachate concentration can be described in terms of the mixing of the open pore solutions with the leachant and dissolution of the blended cement paste. This early stage is followed by continued dissolution and competing reactions such as precipitation. Eventually a steady state or equilibrium is reached in which the leachate concentrations of cesium and strontium approach that in the original pore solution. The model assumes that sufficient quantities of cesium or strontium are available in the blended cement paste to reach the steady state value in the leachate and that the leachant is not renewed or added to with time.