A Study on Self-Healing Mechanism of Microcracks in Concrete Structures Using Bacillus Bacteria

Corrosion of the steel reinforcement in concrete requires manual and costly repair procedures to prevent premature failure of constructions. Although preventive measures during the construction phase are often implemented but early corrosion may still occur. The primary reason for premature corrosion is crack formation in the concrete cover. Larger cracks as well as a network of finer cracks allow water, oxygen, chloride, and other aggressive corroding substances to penetrate the concrete matrix to reach the reinforcement. The objective of the paper described in this proposal is the development and application of a bio-chemical agent which, when incorporated in the concrete matrix, autonomously and actively prevents premature reinforcement corrosion in a twofold mode. The produced bio-minerals block and seal cracks resulting in a delay of further ingress of water as well as to a decrease of inward diffusion rate of chloride and oxygen. Moreover, as the metabolically active bacteria consume oxygen, the agent acts as an oxygen diffusion barrier protecting the embedded passivity steel reinforcement against corrosion. In this way the reinforcement will be protected for substantially increased periods, even after breakdown of the passivity layer, as a lack of oxygen prevents further corrosion.