Scale preparation of core–shell bacterial healing agent for concrete and evaluation of shell protection and core mineralization ability

Abstract

Repairing cracks is a pivotal research direction in the field of concrete. Utilizing bacteria to generate calcium carbonate and fill cracks has demonstrated feasibility. However, the highly alkaline concrete environment hampers the long-term effectiveness of bacteria. Using a carrier to protect the bacteria is considered the most promising solution. Regrettably, there is a notable absence of substantial reports on large-scale manufacturing processes for bacterial healing agents, greatly impeding their widespread application. This study presents a comprehensive large-scale preparation process for core–shell bacterial healing agents to address this knowledge gap. The investigation examines the influence of different binder wetting agent types, calcium source composite processes, and curing systems on the properties of the healing agent. The study examined the influence of different binder wetting agent types, calcium source composite processes, and curing systems on the properties of the healing agent. Additionally, the protective effect of the shell on the core material under extreme environmental conditions was evaluated. The results demonstrate that the healing agent prepared using this process exhibits a core–shell structure, wherein the shell effectively safeguards the bacteria even after experiencing freeze–thaw cycles and high temperatures. The bacteria within the healing agent can mineralize and produce calcite to repair even after 500 d. These research findings provide practical insights for the long-term self-healing performance of concrete, laying a solid foundation for the widespread adoption and promotion of bacterial healing agents.