Review of Using Coal Refuse as Raw Materials for Calcined Clay Cement

To reduce CO₂ in the cement industry, research is being conducted to refrain from using clinkers, and many studies are being conducted and applied abroad on limestone calcined clay cement (LC³). This study conducted a basic study to apply non-kaolinite coal refuse as a calcined clay material. The total contents of SiO₂+Al₂O₃+Fe₂O₃ of the coal refuse, such as the digging refuse (DR) and the coal-preparation refuse (CR) were 95.0 and 92.5 wt.%, respectively, and the Al₂O₃ contents were 21.87 (DR) and 23.04 (CR) wt.%.The main minerals of the two types of refuse were confirmed to be Si-Al based Kaolinite, Pyrophyllite, and Muscovite phases, which appeared to be similar crystal phases. According to the crystal phase analysis by calcined temperatures (650, 750, and 850℃), it is confirmed that the Kaolinite peak is converted to a meta-kaolinine phase, mainly converted to Si-Al based minerals or converted to amorphous ones.The results calculated using method of Diaz et al., Al₂O₃ content and Al₂O₃/SiO₂ produced results that satisfied the criteria, but loss of ignition (LOI) was 20.19 and 12.36 wt.%, respectively, which did not satisfy the criteria of 7wt.% or less. Therefore, coal refuse has the potential to be used as a material for calcined clay cement as a non-kaolin clay material, but further research is needed on the effects of other contained components on cement materials.