Low- and zero-cement frozen backfill within permafrost mining conditions: A review

This review examines the emerging field of unconventional backfilling methods in freezing conditions, specifically tailored for remote mining operations in permafrost regions. Meeting the demand for mineral resources while addressing environmental concerns necessitates innovative approaches in mineral production and mining operations. This review aims to give a very first catalog of novel unconventional backfills in freezing conditions which is being encountered in remote mining areas like permafrost regions. As mining expands into these challenging environments, logistical obstacles, high costs, and environmental considerations arise. Conventional backfilling often relies on cement, which poses economic and environmental challenges due to carbon emissions and costs. Research has explored alternative backfill compositions and deployment strategies. Unconventional mixtures, sometimes without cement or using alternative binders, have gained attention in freezing conditions. Studies suggest that frozen backfill can be stronger than unfrozen alternatives, with water acting as a natural binder during freezing. However, the extended freezing process requires innovative deployment methods and consideration of seasonal limitations. Key findings indicate that faster freezing processes can improve strength, yet the adverse effects of freezing on cement hydration necessitate alternative materials, such as zero-cement backfill and using alternative binders. Despite the promise of unconventional backfilling, several areas still require further exploration. Mechanisms to enhance freezing rates, alternative binder materials, and factors affecting strength and thermal conductivity need continued investigation. In our pursuit of novel backfilling methods, there remains much ground to cover. The main outcome of this review is the identification and evaluation of unconventional backfill materials and methods for use in freezing conditions, highlighting their potential advantages over conventional cement-based backfills. It underscores the need for further research into alternative binders, deployment strategies, and the optimization of freezing processes to enhance backfill strength and address economic and environmental concerns in remote mining areas.