  Microbial-Induced Carbonate Precipitation (MICP) is an innovative ground
improvement technique which can enhance the strength and stiffness of soils,
and can also control their hydraulic conductivity. These engineering properties
of MICP-treated soils are affected by particle-scale behaviour of the
precipitated carbonate, i.e. composition, amount and distribution, which are
controlled by the MICP process occurring at the particle-scale. In this study,
we designed and fabricated a microfluidic chip to improve our understanding of
MICP at particle-scale by observing the behaviour of bacteria and CaCO3
crystals during this process. We found that bacteria became evenly distributed
throughout the microfluidic chip after the injection of bacterial suspension,
grew during bacterial settling, and detached during the injection of
cementation solution. Bacteria aggregated during the cementation solution
injection, and CaCO3 crystals formed at narrow pore throats or open pore bodies
either during or after cementation solution injections.
