1576 CARBON REDUCTION PATHWAYS OF CEMENTED BACKFILL MINING FOR COAL MINES *Xuejie Deng, Ning Jia, Hao Liu, Tongda Zheng, Shike Wang, Qingxiang Liu, Jichu Wang, Yile Zhao, Shuxin Yang China University of Mining and Technology Beijing, School of Energy and Mining Engineering, Beijing, China, 100083 (*Xuejie Deng: dengxj@cumtb.edu.cn) ABSTRACT To mitigate the high carbon emissions associated with cementitious binders in conventional coalmine cemented backfilling, a three-tier carbon-reduction pathway is proposed, including carbon-reduced, low-carbon, and carbon-negative approaches. For the carbon-reduced tier, a performance-driven design framework covering the full life cycle of cemented backfill materials is established. Based on this framework, a dynamic mix-proportion optimization method using a multi-objective targeting strategy is developed and has been implemented in multiple coal mines. For the low-carbon tier, microbially induced carbonate precipitation (MICP) is introduced. Mixing-based and grouting-based microbial cemented backfill materials are prepared, achieving compressive strengths of up to 25.12 MPa. The consolidation mechanism is clarified, and a positive correlation is observed between compressive strength and the content of biogenic calcium carbonate. For the carbon-negative tier, mineralization and carbon sequestration are incorporated into backfill materials. High-porosity carbon-negative backfill materials and microbial carbon-negative cemented backfill materials are developed, with carbon sequestration rates reaching 2.45%. This paper reviews the research on carbon reduction in coal mine cemented backfill conducted by the author's team, aiming to support greener backfill practices. KEYWORDS Coal mine cemented backfill, Carbon reduction pathways, Performance design, MICP, Carbon dioxide 1. INTRODUCTION Underground coal mining operations can trigger environmental issues such as ground subsidence, soil erosion, and solid waste discharge. Cemented backfill provides a solution to these environmental challenges by fill the solid waste back to the underground goaf. A slurry is prepared using solid waste as aggregate and cement as binder. The slurry is transported into the goaf, where a backfill body is formed to support the overlying strata. Traditional coal mine cemented backfilling predominantly employs cement as the binding agent. However, each ton of cement produced emits approximately 1.04 tons of carbon dioxide (CO₂), making extensive cement use inconsistent with green, low-carbon development principles. National targets for peak carbon emissions by 2030 and carbon neutrality by 2060 have been set in China. Decarbonization requirements in coal related industries have been intensified. Recent studies have focused on low-carbon cemented backfilling. Regarding backfill materials (Chen et al., 2022; Liu et al., 2024), studies have focused on low-carbon cementitious materials and green carbon-negative materials. Significant progress has been achieved by utilizing solid waste materials such as coal gasification slag, steel slag, and blast furnace slag to produce novel green cementitious materials as substitutes for traditional cement. Concurrently, by controlling the pore structure of the backfill to sequester CO₂, carbon emissions during backfilling operations have been reduced. Regarding filling process
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