This technology is a self-healing concrete and cement composition that combines a culture of Bacillus missungi AK13 grown in a sesame meal-based medium with calcium-containing inorganic salts extracted from oyster shells using an acidic solution. When cracks form in the concrete, the bacteria metabolize to precipitate calcium carbonate, automatically sealing the gaps.
Concrete is weak in tensile strength compared to compressive strength, making micro-cracks inevitable. These cracks allow chloride ions, carbonates, and sulfates to penetrate, leading to neutralization and rebar corrosion. Previous bio-concrete using bacteria required separate nutrients and calcium sources to support bacterial growth; however, synthetic or commercial media and calcium compounds like calcium lactate or calcium acetate were expensive, driving up production costs. Meanwhile, hundreds of thousands of tons of oyster shells generated annually are mostly discarded, causing social issues like odors, with only a small portion used as fine aggregate.
This technology uses a medium made by autoclaving sesame or soybean meal in distilled water and adjusting the pH to 10 with sodium carbonate, allowing for the low-cost, mass production of bacterial vegetative cells and spores. The culture can be added in raw, concentrated, or dried forms. For crack repair, the composition is applied to the crack, followed by the supernatant from centrifuged sterilized sesame meal extract to boost bacterial activity. It can be used in self-healing mixes for new concrete structures, crack fillers for aging bridges and tunnels, and injection materials for reinforcing soft ground. This recycles agricultural byproducts like sesame meal and fishery waste like oyster shells, while reducing bio-concrete production costs by replacing expensive media and calcium compounds.
This invention was developed with support from the Ministry of Land, Infrastructure and Transport for the development of practical self-healing concrete technology using bacteria.
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