CONVERSION OF WASTE STONE-FINE SLURRY INTO GEOPOLYMER CEMENT WITH ADDITION OF COAL FLY ASH
Keywords:Waste stone-fine slurry, Coal fly ash, Geopolymer, NH4 removal, Alkali reaction
In the crushed stone production process, waste stone-fine slurry is generated as wastewater, and are landfilled as dehydrated cake after some treatments. Recently, it is becoming difficult to secure landfill sites, and effective utilization of by-products, dehydrated cake, is desired. On the other hand, a large amount of coal fly ash was discharged from a coal-fired power plant, due to the operation suspension of nuclear power plants since the Fukushima nuclear accident occurs. In this study, we attempted to prepare geopolymer cement from waste stone-fine slurry with addition of coal fly ash. Waste stone-fine slurry used in this study was discharged from one of the quarries in Japan. NaOH solution was added into the slurry, and heated at 60 - 180 oC for 0 - 24 h to obtain the high Si solution for preparation of geopolymer cement. After heating, the slurry was cooled to room temperature by quenching with tap water, and various amounts of coal fly ash were added, mixed, and cured at 80 oC for 24 h. The strength and water purification ability of the product was examined. The solution with high Si content to prepare the geopolymer can be obtained at 120 oC for 9 h in 4 - 8 M NaOH solution, and the products obtained from 6 - 8 M NaOH slurry solution with addition of 0.55 - 0.70 weight ratio of coal fly ash have higher strength than other products and Portland cement. The product indicates NH4+ removal ability for wastewater treatment.