Virginie Wiktor e-mail: v.a.c.wiktor@tudelft.nl
Lupita Sierra Beltran e-mail: m.g.sierrabeltran@tudelft.nl
Renee Mors e-mail: R.M.Mors@tudelft.nl
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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, such as application of a several cm-thick concrete cover layer, 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 study 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 bio-chemical agent, consisting of a mixture of bacteria and calcium lactate, produces when activated by ingress water calcium carbonate-based minerals by metabolic conversion of calcium lactate. 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 passivated steel reinforcement against corrosion. In this way the reinforcement will be protected for substantially increased periods, even after breakdown of the passivated layer, as a lack of oxygen prevents further corrosion. Incorporation of the agent in concrete will be relatively cheap as well as easy when the agent is immobilized in porous light-weight aggregates prior to addition to the concrete mixture. It is expected that the application of the proposed sustainable bio-chemical healing agent will result in substantially decreased maintenance and repair costs of steel-reinforced concrete structures.
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