## Materials and Methods
### Cement Mortar Test Piece Preparation and High-Temperature Damage Test Method  
A 40 \(\times\) 40 \(\times\) 160 mm cement mortar specimen was prepared according to the mix ratio specified in Table 2. The specimen was left to cure for 28 days in an environment with a relative humidity of over 90% and a temperature of 20 \({}^{\circ}\)C \(\pm\) 1 \({}^{\circ}\)C. Six specimens were prepared for each of the following groups: the original group, the high-temperature unrepaired group, and the high-temperature repaired group. The temperature inside the test piece was maintained at the set temperature of the resistance furnace for 15 min. Subsequently, the specimen was removed from the furnace and cooled using a method that simulated firefighting conditions. Immediately after removal from the oven, the specimen was cooled in a running basin of water. The test block was then dried indoors and set aside. The high-temperature damage test was conducted using a box-type resistance furnace with a rated voltage of 220 V, an output power of 15 kW, and a maximum operating temperature of 1200 \({}^{\circ}\)C. The heating rate was set at approximately 10 \({}^{\circ}\)C/min. The furnace dimensions were 600 mm \(\times\) 400 mm \(\times\) 400 mm (L \(\times\) W \(\times\) H). The target temperature for the test was 500 \({}^{\circ}\)C. The heating process is as follows: the cement mortar specimen was heated in the furnace. The internal temperature of the sample was measured using a thermocouple. When the temperature of the specimen was equal to the temperature of the resistance furnace, the furnace door was opened to allow the specimen to cool for 1.5 h. The load and repair test was carried out after natural cooling to room temperature. Compressive strength was evaluated using an electro-hydraulic servo universal testing machine with a loading rate of 2.4 kN/s. Results were accurate to 0.1 MPa. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Species** & **Tryptone (g)** & **Bean Peptone (g)** & **NaCl (g)** & **Agar (g)** & **Urea (g)** & **Deionized Water (mL)** \\ \hline Solid medium & 15.0 & 5.0 & 5.0 & 15.0 & 20.0 & 1000.0 \\ Fluid medium & 15.0 & 5.0 & 5.0 & 0 & 20.0 & 1000.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Medium mix ratio. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Cement (g)** & **Sand (g)** & **Fly Ash (g)** & **Water (g)** & **Mineral Powder (g)** & **Metakaolin (g)** & **Silica Ash (g)** \\ \hline
315 & 1350 & 90 & 202.5 & 0 & 45 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cement sand specimen mix ratio. Experiment and Characterization of Microbial Mineralization Restoration of High-Temperature Damaged Cement Mortar Specimens  
The repair test was conducted by immersing the high-temperature damaged specimen in a mixture of bacteria solution, urea, and C4H6 CaO4:H2O for 24 h. It was then dried at room temperature, and its multi-scale performance before and after restoration was compared. The multi-scale performance of the specimen before and after restoration was compared. A compression test was used for macroscopic characterization. The chloride-ion transfer coefficient test was conducted utilizing the vacuum negative pressure adsorption method. The RCM-6H multifunctional concrete durability comprehensive tester was used for the test. The instrument had six channels and could measure six specimens simultaneously. It was equipped with temperature and current monitoring sensors and can display temperature and current in real time. The temperature display had an accuracy of 0.1 \({}^{\circ}\)C, while the current display had an accuracy of 0.01 mA. A SHZ-III vacuum pump was utilized, with a maximum vacuum degree of 10 kPa. The defoaming barrel was a custom-made cast iron vacuum cylinder with a transparent barrel cover that allowed observing the inside of the barrel at all times. The specimen was prepared according to the mixing ratio given in Table 2. The mold was a 100 \(\times\) 150 mm cylinder during molding.