Monitoring of the enzyme induced calcite precipitates simultaneously with spectral induced polarization and bender elementtechnique

Enzyme induce calcite precipitation (EICP) emerges as an alternative soil improvement method to microbial induced calcite precipitation (MICP) with the advantage of simplicity for both engineering applications and scholarly mechanisms unveiling.On the other hand, it is well received that both complex conductivity (CC) and shear wave velocity (Vs) are sensitive to the formation of calcite precipitates. Aspectral induced polarization-bender element (SIP-BE) column was developed to measure both CC and Vs. A mixture of a uniform sand (Ottawa 50-70)and urease (enzyme) was packed in the column, and urea and CaCl2solutions were introduced to the column to generate calcite precipitates. Solid content (SC) postulated from the chargeability from SIP results was found to agree well with theoretical values calculated from the inflow and outflow conductivity; Shear wave velocity increment was proportional to (SC)0.6, suggesting a preferential precipitate attachment at particle contacts, especially at SC < 0.68%. Both the preferential attachment and the mean particle size calculated from Schwarz equation agreed well with SEM imaging. Those findings suggest that simultaneously use of SIP and BE can yield unique information about the progress of EICP, and hold promising applications in monitoring the generation of MICP and biofilms.