Sand solidification technology is widely applied in engineering. This paper presents experimental methods to analyze the effect of adding urea to a culture medium for sand solidification. The results show that adding urea to the culture medium increases urease activity and inhibits bacterial growth, and the optimal amount of added urea is between 5 and $20\mathrm{g}/\mathrm{L}$ . Adding urea after sterilization markedly increases the strength of the injecting path for sand column solidification. However, a long injecting path leads to differences in strength between the entrance section and middle section, resulting in lower overall strength. The faster the injection speed, the higher is the overall strength of the sand columns. When $20\mathrm{g}/\mathrm{L}$ of urea is added, the overall strengths of the solidified sand columns increase with larger sand particle size. Adding different amounts of urea is suitable for the solidification of corresponding sand column sizes. Therefore, adding urea to the culture medium for sand solidification is significant for various sand particle sizes. The results will act as a guide for the application of sand solidification technology.

Microbially induced corrosion (MIC) on concrete represents a serious issue impairing the lifespan of coastal/marine infrastructure. However, currently developed concrete corrosion protection strategies have limitations in wide applications. Here, a biomineralization method was proposed to form a biomineralized film on concrete surfaces for corrosion inhibition. Laboratory seawater corrosion experiments were conducted under different conditions [e.g., chemical corrosion (CC), MIC, and biomineralization for corrosion inhibition]. A combination of chemical and mechanical property measurements of concrete (e.g., sulfate concentrations, permeability, mass, and strength) and a genotypic-based investigation of formed concrete biofilms was conducted to evaluate the effectiveness of the biomineralization approach on corrosion inhibition. The results show that MIC resulted in much higher corrosion rates than CC. However, the biomineralization treatment effectively inhibited corrosion because the biomineralized film decreased the total and relative abundance of sulfate-reducing bacteria (SRB) and acted as a protective layer to control the diffusion of sulfate and isolate the concrete from the corrosive SRB communities, which helps extend the lifespan of concrete structures. Moreover, this technique had no negative impact on the native marine microbial communities. Our study contributes to the potential application of biomineralization for corrosion inhibition to achieve long-term sustainability for major marine concrete structures.