1584 mechanism is elucidated, revealing that CaCO3 crystals generated within the material effectively fill the internal pores and cement adjacent particles together. High-porosity carbon-negative backfill materials and microbial carbon-negative cemented backfill materials are successfully developed. Their mechanical and carbonation properties are systematically evaluated, and the carbonation-cementation mechanism is revealed. The uniaxial compressive strength of the microbial carbon-negative materials reaches 3.28 MPa, with a carbonation rate of up to 2.45%. ACKNOWLEDGEMENTS Sincere gratitude is expressed to the team led by Professor Xiaohui Cheng at Tsinghua University for assistance with microbial experiments. Appreciation is also extended to all experts and scholars who provided support to this study. This work was supported by the National Natural Science Foundation of China (Grant Nos. 52474162, 52274149) and the Deep Earth Probe and Mineral Resources ExplorationNational Science and Technology Major Project (No. 2024ZD1003905). REFERENCES Chen Q., Zhu L., Wang Y., Chen J., Qi C., (2022). The carbon uptake and mechanical property of cemented paste backfill carbonation curing for low concentration of CO2. Science of the Total Environment. 852: 158516. Deng X., Li Y., Liu H., Zhao Y., Yang Y., Xu X., Cheng X., Wit B.d., (2021). Examining energy consumption and carbon emissions of microbial induced carbonate precipitation using the life cycle assessment method. Sustainability. 13, 4856. Deng X., Yuan Z., Li Y., Liu H., Feng J., Wit B.d., (2020). Experimental study on the mechanical properties of microbial mixed backfill. Construction and Building Materials. 265, 120643. Deng X., Li Y., Lu D., Zheng T., Zhang J., Wu Z., Xu X., Wit B.d., (2024). Cementing mechanism of MICPtreated mortar and performance improvement by innovative molds. Journal of Materials in Civil Engineering. 36(7): 04024150. Guo Q., Zhang J., Li M., Huo B., Zhao Y., Yin Z., Xing S., Fu X., (2025). Rheological and CO2 sequestration properties of alkali-activated gangue-based backfill slurry: Effect of temperature. Journal of Materials Research and Technology. 36: 3886-3897. Han Z., Li D., Zhao Y., Wang J., Guo N., Yan H., Han C., Li Q., Tucker M., (2022). Mineralogy of Bioprecipitate evolution over induction times mediated by halophilic bacteria under various Mg/Ca molar ratios. Acs Omega. 7: 29755-29772. Hefni M. and Hassani F., (2020). Experimental development of a novel mine backfill material: Foam mine fill. Minerals. 10(6), 564. Liu L., Xia L., Fang Z., Jia Q., Gao Y., He W., Liu Z., (2024). Performance study of modified magnesiumcoal based solid waste negative carbon backfill material: Strength characteristics and carbon fixation efficiency. Journal of Environmental Chemical Engineering. 12: 113281. Lin X., Li W., Guo Y., Dong W., Castel A., Wang K., (2023). Biochar-cement concrete toward decarbonisation and sustainability for construction: Characteristic, performance and perspective. Journal of Cleaner Production. 419: 138219.
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