DEVELOPMENT OF A MICROBIAL-BASED GROUTING MATERIAL WITH CALCIUM CARBONATE PRECIPITATES

Bio-concrete, which is a concrete with self-repair capability provided by microorganisms, is attracting much attention. In recent years, crack repair grouts based on microbial metabolism have been studied. Because such grouts are flowable aqueous solutions, they differ greatly from grouts based on inorganic or organic compounds and are expected to penetrate into cracks in concrete by capillary action. Therefore, press fitting of bio-grouts is unnecessary. As an additional advantage, these grouts do not impose a load on the environment. In this study, we performed benchtop experiments using conical tubes with a large amount of calcium source. The experimental results show that the addition of a large amount of calcium shows no substantial change in the amount of precipitate. In addition, the amount of precipitated crystals did not substantially differ even when the type of calcium salt was varied. Prolonging the standing time was led to crystal growth, and the amount of precipitates obtained increased. As a result of scanning electron microscopy observations of the crystals obtained under each growth condition, we confirmed that many yeast cells were mixed in the crystals. However, difference was observed in the crystal structure when calcium salt was varied. Moreover, Calcium carbonate formation was observed on concrete as a preliminary experiment for the crack repair of concrete. Crystals were generated even at room temperature, and better results were obtained when the temperature was set to 40 °C.