Keywords: Concrete structures, cracks, durability, repair, East bacteria, Bacillus bacteria, calcium carbonate, alkali-silica reaction, moisture penetration.
Concrete has low tensile strength, making it prone to cracking. Moisture and harmful ions can penetrate the interior of the concrete through these cracks, potentially affecting the long-term durability of the structure. Traditional repair methods often involve injecting or filling repair materials and covering the cracked surfaces with waterproofing materials; however, there is a possibility of re-cracking or deterioration of the covering layer, as well as environmental concerns due to the outflow of repair materials during construction.
On the other hand, in recent years, innovative repair methods using microorganisms have been proposed. This technique involves the reaction between carbon dioxide, a metabolic product of microorganisms, and calcium ions in the cracks, resulting in the formation of calcium carbonate that seals the cracks. In addition to reducing environmental impact through the use of harmless microorganisms, there is a potential advantage that if the microorganisms continue to live in the repaired area, they can seal the cracks again when they reoccur.
Currently, research and development of crack repair materials using microorganisms such as yeast and Bacillus are underway, and experiments have confirmed that after repair, the cracks were sealed, and the penetration of moisture, which is a factor of deterioration, significantly decreased compared to before the repair.