## 1 Introduction  
Fire is currently the most significant danger to buildings [1]. When concrete structures are exposed to high-temperature fires suddenly, they experience degraded material properties, increased deformation and cracks, weakened structural strength, and reduced safety and durability. Fire and high temperatures result in severe damage to concrete materials due to a series of physical and chemical changes, such as phase transitions in cement stone, increased cracks, and a porous and loose structure. Furthermore, the cracking and disjointness of the cement stone-aggregate interface contribute to the damage. As a result, concrete damage caused by fire tends to progress gradually from the surface to the interior, with most of the damage defects manifesting as cracks [2; 3]. Although many repair materials are available for fixing concrete cracks, most of them consist of organic polymer materials, which are incompatible with cement-based materials. Additionally, some of these materials have harmful and pathogenic characteristics. Biomineralization, which is dependent on Biologically Induced Calcium Carbonate Precipitation Technology (MICP), uses biological metabolic activities to induce calcium carbonate precipitation and repair cracks in concrete. Biomineralization technology has the advantage of being environmentally friendly, and the calcium carbonate generated is highly compatible with cement-based materials [4; 5; 6]. [PERSON] and [PERSON] [7; 8; 9; 10; 11] conducted research to investigate the formation mechanism of microbially mineralized calcite in self-healing concrete. They discovered that concrete crack self-healing bacteria produced calcite-type CaCO\({}_{3}\) as a mineralization product and identified the necessary factors and chemical changes in the mineralization process. The study on the yield of calcite mineralized by microorganisms revealed that different substrate concentrations, medium concentrations, n(MgSO\({}_{4}\))/n(CaCl\({}_{2}\)), and inoculum amounts significantly influence the calcite yield. Their research also revealed that with an increase in age, the number of calcium carbonate crystals slightly larger than 1 mm in concrete cracks increased, while the crack width gradually decreased. After around 40 days, calcium carbonate crystals had effectively filled the cracks on the surface. Although urease activity has been found in numerous species of microorganisms, only in a few microorganisms, represented by Bacillus cereus, has very high urease activity been found and induced biomineralization reactions. At the beginning of the 21 st century, [PERSON] [12] was the first to carry out a study on the differences in urease activity among multiple species and found that microbial urease activity was generally higher than that of plants and animals, but urease activity in microorganisms also shows significant inter-species differences exist. Among them, the urease activity of Helicobacter pylori is at a high level among microorganisms [13,14], while the urease activity of _Aspergillus_ spp. is relatively low [15] and even comparable to that of plants. The species with the highest known urease activity is _Sporoscrina pasteurii_[16], whose overall expression of urease genes reaches even 1 percent of its cell dry weight [17]. [PERSON] and [PERSON] [18] utilized microbial-induced calcium carbonate deposition technology for repairing the surface of cement-based materials with defects, where they also studied the surface formation. Moreover, they applied a high concentration of bacteria to the surface of the material with defects and noted the formation of a sediment film about 100 um thick on the top horizontal layer. As a result, the water absorption rate of the component decreased by approximately 85%, and the repair effect of the topmost layer was superior to that of the side. The researchers also tested the strength of the cracks repaired using microbial technology.