Event: 5th International Workshop on Induced Polarization, Newark (USA), October 2018
Abstract by Satoshi Izumoto, Johan Alexander Huiman, Egon Zimmermann, Odilia Esser, Franz-Hubert Haegel, Harry Vereecken
Induced calcite precipitation is used in a range of geotechnical applications to improve the mechanical properties of porous media. It has been shown that spectral induced polarization (SIP) allows to monitor calcite precipitation, although results were partly inconsistent. Therefore, this study aims to investigate how the SIP response of calcite depends on solute composition, since this may explain the differences in previous studies. SIP measurements were made on a column filled with sand while calcite precipitation was created by injecting Na2CO3 and CaCl2 solutions through two different ports. The experiment consisted of five phases. In phase I, calcite precipitation was generated for a period of 12 days. This resulted in a well-defined calcite precipitation front, which was associated with an increase in the imaginary conductivity. In phase II, the injected solutions were increasingly diluted. This resulted in a clear decrease in imaginary conductivity. In phase III, the injection of the two solutions was stopped. Nevertheless, calcite precipitation continued and solute concentrations in the mixing zone decreased. As in phase II, this led to a decrease in the imaginary conductivity. In phase IV, the injection rate of the Na2CO3 solution was reduced to shift the mixing zone, which also decreased the imaginary conductivity. Finally, the column was flushed with a solution in equilibrium with calcite in phase V, which led to a very small SIP signal. These results imply that calcite only generates a SIP response when it is in contact with solution which is strongly oversaturated with respect to calcite.
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