Microscopic insights into MICP treated fly ash

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Historically, the byproducts of coal combustion are either used beneficially in products (e.g., concrete, wallboard) or are land disposed in ponded storage facilities or landfills. However, long term storage of ponded ash can result in mechanical stability issues or in leaching into groundwater, making the precipitation of a binding matrix desirable from both a geotechnical and environmental perspective. The present study provides microscopic insights into the applicability and effect of using microbially induced calcite precipitation (MICP) on fly ash. MICP column experiments were performed on a loosely packed fly ash material and bio-cemented samples were preserved for SEM imaging. SEM observations showed the presence of microbial cells, with some cells growing to roughly the same scale as the smallest fly ash spheres. The presence of microbial colonies in the bio-cemented fly ash samples indicated that biological activity was occurring in fly ash. The precipitated calcite crystals formed a cementation matrix in which the fly ash particles were embedded rather than forming particle-to-particle cementation bonds between individual fly ash particles owing to the small size of tested fly ash particles, and resulted in larger aggregated units of cemented fly ash particles.

2025 International Conference on Bio-mediated and Bio-inspired Geotechnics (ICBBG2025)

General session: Bio-mediated methods for environmental protection and restoration