## 1 Introduction  
After exposure to high temperatures, the mechanical properties and durability of concrete structures will be affected to varying degrees. [PERSON] et al. [1] tested the mechanical properties of C70 and C85 high-strength concrete (HSC) after high temperature, they found that the HSC specimens explosive spalled when heated to 500 \({}^{\circ}\)C, and the average compressive strength loss of the two kinds of HSC was 63.2% and 49.2%, respectively, at 500 \({}^{\circ}\)C. [PERSON] et al. [2] measured the chloride ion permeability of C20, C40, and C60 concrete, the results showed that the chloride ion migration coefficient of concrete increased significantly with the increase of temperature, the chloride ion migration coefficient of C60 concrete specimens even reached 12.3 \(\times\) 10\({}^{-12}\) m\({}^{2}\)/s at 800 \({}^{\circ}\)C. [PERSON] et al. [3] studied the mechanical properties and microstructure of C60 high-performance concrete (HPC) at 20-600 \({}^{\circ}\)C using X-ray computed tomography (X-CT) technology. They found that as the temperature increased, the compressive strength of HPC showed a decreasing trend. This was because the microstructure of concrete deteriorated with the increase in temperature, and the length, width, area, and girth of cracks exhibited an increasing trend. In order to deal with high-temperature concrete damage, some researchers proposed reinforce or repair methods. [PERSON] et al. [4] reinforced ordinary concrete (OC) and HPCthat have gone through fire by increasing cross-section method. The results showed that the compressive strength of HPC reinforced with carbon fiber cloth increased by 38%, while the HPC reinforced with fiber glass had an improvement of ductility while restoring its compressive strength. [PERSON] et al. (2016) prepared graphite oxide and silane composite solution to repair high-temperature damaged concrete. They found that the penetration depth of the composite solution in concrete reached more than 9 mm, and formed a certain thickness of hydrophobic layer, thus improved the impermeability of the damaged concrete. The above reinforce and repair methods restored the performance of damaged concrete to some extent. However, the reinforce method increased the cross-section area and self-weight of the concrete components, while the repairing agents were prone to aging and had poor long-term performance. High-temperature damage in concrete is the result of multi-factor and multi-scale damage that spreads from the surface to the center and mainly manifests as defects such as looseness, spalling and cracks ([PERSON] et al., 2016). When concrete is subjected to high temperatures, most of the resulting surface cracks are macroscopic; in particular, the number of cracks smaller than 1 mm increases significantly, and the interior of the concrete is loose and porous with 6-50 \(\upmu\)m cracks ([PERSON] et al., 2016). Microbes, repair fluid and oxygen can easily enter the interior of the concrete through these cracks. Therefore, it is possible to introduce mineralizing microbes into damaged concrete within a specific repair fluid, where they can mineralize and deposit calcium carbonate (CaCO\({}_{3}\)) crystals to fill the internal and surface defects, thus repairing the damaged concrete. This process of microbial mineralization is called MICP. MICP is a mineralization reaction that involves the transformation of ions in solution into solid minerals under certain physical and chemical conditions and under the control of microbial organic substances at specific sites of microbes ([PERSON] et al., 2016). The mechanism is shown in Figure 1. The sediment produced by MICP is CaCO\({}_{3}\), which has good compatibility with concrete and will not harm the environment in the repair process or with long-term service. NH\({}_{4}\)\({}^{+}\) is the byproduct of MICP, which convert into NH\({}_{3}\) in the solution and then release into the atmosphere, however, NH\({}_{4}\)\({}^{+}\) and NH\({}_{3}\) can be adsorbed by adding zeolite powder in the solution.