Observation of Calcium Carbonate Precipitation Process and the Permeability Experiments by EICP using Microfluidic Chip

Abstract

EICP (Enzyme Induced Calcite Precipitation), which artificially precipitates calcium carbonate using urease purified from enzymes found in leguminous plants, is attracting attention as a ground improvement method with low environmental impact. Many mechanical and permeability tests have been conducted on treated soil modified by the EICP technique, but there is a need for a technique that enables microscopic observation of the calcium carbonate precipitation process. In this study, we injected a grouting solution into a microfluidic chip using the EICP technique, and observed the precipitation process of calcium carbonate to examine the precipitation mechanisms in the pores. The area of precipitated crystals was quantitatively evaluated by using image analysis software. In addition, we developed a device that can measure the differential pressure before and after the chip and the flow rate of permeate water, and conducted permeability experiments to investigate the water sealing effect of grout injection on a micro scale. As a result, the precipitation of calcium carbonate crystals by grout injection was confirmed. The change in porosity was quantitatively evaluated by the image analysis, and the qualitative change of permeability was understood.

Keywords

• calcium carbonate precipitation
• eicp
• permeability
• microfluidic chip