## 1 Introduction
Through a compressive strength test and scanning electron microscope observation and analysis, it was found that microorganisms produced products in the pores, which beneficially changed the porosity and pore size distribution of cement mortar and improved the mechanical properties of cement mortar. [PERSON] et al. [17] also discussed the influence of microbial concentration on the compressive strength and crack self-healing performance of cement mortar. The results showed that under the same mixture of microorganisms and cement mortar, the concentration of microorganisms would affect the precipitation mode of calcium carbonate, which is the key reason for affecting the compressive strength and self-healing performance of cement mortar. [PERSON] et al. [12] focused on the activity of microorganisms during the self-healing process of concrete cracks. The results showed that the activity of microorganisms showed an obvious downward trend. [PERSON] et al. [18] studied the influence of a microbial calcium source on concrete performance. The mechanical properties, durability, and self-healing properties of concrete were analyzed by adding different concentrations of calcium lactate and comparing the conditions without adding calcium lactate. The results showed that calcium lactate had a positive effect on the performance of concrete mixed with microorganisms. [PERSON] et al. and [PERSON] et al. [19; 20] both used expanded perlite to immobilize microorganisms and added them to concrete, and analyzed the self-healingperformance of cracks in the concrete. The results showed that expanded perlite could be used as a new carrier of microorganisms, and cracks in concrete exhibit more efficient self-healing properties. This indicated that expanded perlite had a significant protective effect on microorganisms and promoted the self-healing of cracks. Environmental conditions within the concrete, external nutrients, and the precipitation medium also influence the mineralization activity of microorganisms, thereby affecting the healing efficacy of the concrete [21; 22]. During the metabolic reaction of microorganisms, the released components, products, and their compatibility with concrete are important factors in enhancing the cohesion of concrete and improving the healing effect of concrete [23; 24]. Additionally, it is not only the basic research of microbial mineralized technology that has been carried out, but also the application is carried out in civil engineering. For example, the demonstration application of microbial self-healing concrete on the side walls of underground engineering has achieved remarkable results [25]. This technology can significantly improve the durability and safety of concrete structures, reduce maintenance costs, and extend the service life of the project. As a composite material, concrete's physical properties can be significantly affected by the addition of admixtures. Recent studies have shown that incorporating silica as an admixture enhances both the mechanical properties and durability of concrete at the early and final stages [26; 27; 28; 29; 30]. Among these, the addition of nano-scale silica has a particularly notable impact on enhancing the mechanical properties of concrete. Nano-silica improves particle distribution by filling voids, reduces concrete porosity, and reacts with calcium hydroxide (Ca(OH))\({}_{2}\)) to produce calcium silicate hydrate (C-S-H) through a pozzolanic reaction (Ca(OH)\({}_{2}+\) SiO\({}_{2}+\) H\({}_{2}\)O \(\rightarrow\) C-S-H). Additionally, nano-silica's large specific surface area promotes the hydration reaction of cement, further improving the early strength of concrete [31; 32; 33]. Adding micron-scale silica can also effectively improve the compressive strength and durability of concrete. On the one hand, the particle size of micron-scale silica is more suitable for filling the pores in concrete and improving the mechanical properties of concrete.