The use of low alkalinity MgO-SiO2 formulation to encapsulate bacteria for self-healing concrete

Concrete structures are inherently brittle, rendering them susceptible to cracking, which in turn allows moisture, carbon dioxide, and harmful ions to penetrate, ultimately resulting in a loss of durability and strength. Incorporating encapsulated or immobilized bacteria in concrete has proven to be an effective way to promote the selfhealing of cracks. However, the commonly used bacteria-based capsules and carriers tend to significantly reduce the matrix strength. To address the strength reduction while facilitating self-healing, the present study proposes utilizing the MgO-SiO2 formulation, a low alkalinity cementitious system, for encapsulating bacteria in selfhealing concrete. Results showed that the incorporation of the capsule can maintain the strength of a cement paste. Furthermore, the addition of the capsule to the PC paste can engage effective self-healing. Cracks between 250 and 350 & mu;m can reach 97% closure while cracks between 350 and 600 & mu;m can reach 85% of closure, and the water passing through the crack reduced around 80% after 40 wet/dry conditioning cycles. Besides, the capsule possessed long-term stability where the concentration of viable bacteria remained stable in the capsule.

Automated summary

Encapsulating bacteria in self-healing concrete using the MgO-SiO2 formulation can maintain the strength and promote effective self-healing. The capsule showed long-term stability with stable concentration of viable bacteria.