Keynote Address: Assessment of geotechnical properties of cemented coal fly ash backfill

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Çavuşoğlu I., Yılmaz E., Yılmaz A. O.

3rd International Conference on Opencast Mining Technology & Sustainability, Singrauli, India, 22 - 23 January 2021, pp.30-40

  • Publication Type: Conference Paper / Full Text
  • City: Singrauli
  • Country: India
  • Page Numbers: pp.30-40
  • Recep Tayyip Erdoğan University Affiliated: Yes


Abstract —The use of coal mining wastes (e.g., fly ash) in the construction materials are poor to effectively manage such high amounts of existing and ever-increasing wastes. Hence, there is an urgent need to search for alternate techniques or ways to reuse/recycle and hence lessen the surface discharged amounts of coal wastes. In this study, cemented coal fly ash backfill (CCB) was utilized as a ground support element in a Turkish lignite coal mine. To reduce the cement-related costs, CCB samples were prepared by using a fly ash content of 75%, 77.5%, and 80% as a function of curing time (2, 7, 28, and 90 days). The fresh (e.g., slump and setting time) and hardened (e.g., compressive strength and mercury porosity) geotechnical properties of CCB samples were investigated in the laboratory. Results illustrate that, at a constant slump value (20 cm), the backfill containing a fly ash content of 75%, 77.5%, and 80% provided a water/cement (w/c) ratio of 0.99, 1.08, 1.19. The w/c ratio of CCB increases from 0.99 to 1.19 due to the decreased cement amount (25% to 20%) which led to the strength reduction of backfill formulated with high amounts of fly ash. Finally, understanding the geotechnical properties of CCB mix still remains critical for the ultimate design of an effective and efficient CCB material for underground mines.

Keywords—cemented coal fly ash backfill; setting times; slump; water/cement ratio; compressive strength; porosity