Marine domestication of Sporosarcina pasteurii induces the precipitation of CaCO3 to solidify calcareous sand

Abstract

The construction of island reef projects using natural seawater, tailored to local conditions, holds significant importance for the advancement of environmentally-friendly geotechnical engineering practices. Previous studies on the application of MICP technology in a seawater environment have been scarce. In this study, Sporosarcina pasteurii were acclimatized to a seawater environment and employed for MICP mineralization reinforcement of calcareous sand, resulting in an enhanced mineralization effect compared to previous attempts under similar conditions. Both direct domestication and gradient domestication methods proved successful in enabling Sporosarcina pasteurii to adapt effectively within a seawater environment. Following domestication, the amount of CaCO3 generated through MICP solidification increased from 2.30% to 4.47%, resulting in a corresponding increase in the Ca2+ conversion rate from 5.19% to 10.02%. Additionally, after domestication, the unconfined compressive strength (UCS) reached up to 309kPa – representing an impressive improvement of 35.53% compared to pre-domestication levels, however, it should be noted that its reinforcement effect still falls short when compared with pure water conditions. The CaCO3 minerals formed after MICP reinforcement using seawater nutrient solution in domesticated Sporosarcina pasteurii predominantly consist of needle-shaped aragonite and granular anorthite minerals, as opposed to the previously observed calcite-type CaCO3 minerals.