Mechanical properties and carbon sequestration potential of MICP-based shotcrete partially substituted with industrial solid waste

Reducing the substantial carbon dioxide emissions from mining activities is essential for establishing environmentally friendly mines and achieving carbon neutrality in the mining industry. This study introduces a practical approach for reducing carbon dioxide emissions in underground mining by leveraging shotcrete, a widely used material in mining, as a carrier for carbon mineral sequestration. Additionally, to further mitigate the overall carbon footprint related to the shotcrete preparation, we enhanced the carbonation process by utilizing bacteria and incorporating solid waste materials as ordinary Portland cement substitutes (mainly yellow phosphorus slag and coal gasification slag). Our research reveals that shotcrete containing bacteria microorganisms exhibits significantly enhanced carbonation rates compared to conventional shotcrete. Specifically, it absorbs approximately 0.76 kgCO2 per square meter within a span of 14 days. Moreover, the substitution of solid waste materials fixed with bacteria not only enhances the mechanical performance of the shotcrete but also further augments the bacterial carbonation ability. Characterization techniques, such as XRD and SEM/EDS, reveal the presence of captured carbon dioxide in the form of calcite, pyrrhotite, and magnesite, resulting in a denser cementitious matrix and improved mechanical properties.