Whole-tailings backfilling materials with fly ash

Grade Ⅰ and grade Ⅱ fly ashes were chosen to produce a cementitious material to replace traditional cement using lime and flue gas desulphurization gypsum(FGD) as stimulation agents.Whole-tailings backfilling samples were prepared with the ratio of the cementitious material to whole-tailings being 1:4 and the ratio of water to the cementitious material being 1:1.The compressive strengths of the whole-tailings backfilling samples cured under the conditions of 45±1℃ for 3d and 20±1℃ for 28d are 5.432 MPa and 3 to 7 MPa,respectively.This generally satisfies the requirement of cemented backfilling for underground mining.Besides,relationship curves between the mass fraction of slurries and the slump were obtained and the mass fraction of the pumpable paste backfilling with the cementitious material is from 80.5% to 83.0%.By the analyses of X-ray diffraction and scanning electron microscopy,hydration products of the cementitious material are mainly gel,ettringite and calcite.