Self-Healing of Cracks in Concrete Using Bacillus Strains Encapsulated in Sodium Alginate Beads

This research focused on the self-healing of micro-cracks in concrete by using different Bacillus strains. The encapsulation of strains in sodium alginate was protected with the bacterial mass, which prevented them from leaching. A viability test was performed to check the viability of bacteria in the highly alkaline environment. The encapsulated bacterial mix having 2-3% of total volume of concrete cubes was effective without compromising compressive strength. The calcium carbonate (CaCO3) precipitation was observed under urease activity. The SEM (Scanning Electron Microscope) revealed the direct involvement of ureolytic bacteria in CaCO3 precipitation. A 16% increase in compressive strength in concrete and significant healing was achieved with Bacillus Subtilis. However, with Bacillus Anthracis, only 6% increase in the concrete strength was achieved. Moreover, the Bacillus Pasteurii did not give effective results. Bacillus Subtilis provided better results than the other strains. The bacterial culture in sodium alginate beads within 2-3% was optimum for compressive strength and self-healing of cracks.