Potential uses and cementing mechanism of bio-carbonate cement and bio-phosphate cement

Bio-cement, based on microbial-induced mineralization, can consolidate the loose particles and be applied to foundation reinforcement, dust control, desert settlement, repair cementitious materials crack, and other fields. In the paper, two kinds of bio-cement, such as bio-carbonate cement and bio-phosphate cement, were discussed as novel binders. The calcium carbonate (calcite), induced precipitation via Sporosarcina pasteurii, could cement between loose sandy soil particles. A series of sand-cemented experiments were conducted to confirm the cemented properties, and a numerical model based on the distribution of the concentration of Sporosarcina pasteurii was established to further analyze bio-grouting process. The evolution law of microstructure was revealed by X-ray computed tomography (X-CT) technique. The atomic binding energy of C-O bond in calcium carbonate, Si-O bond and Si in sand analysis showed that microbial-induced calcium carbonate interacted with surface of loose sand particles formed the intermolecular hydrogen bond. The other kind of bacteria (Bacillus subtilis) could hydrolyze organic phosphate monoester and released PO43-, which could react with different metal cations formed bio-phosphate minerals. The bio-phosphate cement can be used as treatment of sandy soil foundation, functional materials, remediation of heavy metals in contaminated soil, and so on.