Abstract: A new urease-producing bacteria was isolated from the natural environment in the southern humid and hot area of China, and its high-yielding mutant strain was applied to the sea sand indoor MICP grouting test. To study the crystallization phenomenon of calcium carbonate, the Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), and Raman were used to observe the microstructure of the treated samples. By analyzing the basic characteristics of calcium carbonate, such as the morphology, size, spatial distribution, and crystalline state, the regulatory effect on the growth of calcium carbonate crystals and the effect of solidifying soil of the urease-producing bacterial were initially explored. The results show that it is feasible to solidify the soil with urease-producing bacteria in the southern hot and humid area, but the morphology of calcium carbonate crystals is not uniform. The crystal crystallization process, biological regulation and soil structure will all affect the formation of calcium carbonate. In addition, the crytallization of calcium carbonate is from disorder to order, dispersion to aggregation, unstable to stable, and the calcium carbonate eventually develops into a complete and large aggregates in an environment with sufficient growth space. Conclusions in this paper can be used as reference for further study on the action process and regulation mechanism of calcium carbonate precipitation induced by different urease-producing bacteria.

Key words: MICP, urease-producing bacteria, calcium carboante, crystallization phenomenon