Study on properties and microstructure of fly ash-flue gas desulphurization gypsum filling material

In order to effectively dispose the fly ash (FA) and flue gas desulphurization gypsum (FGD), two major industrial wastes of power plants, to realize the resource utilization of solid waste in thermal power plants, the FA and FGD are mixed with quicklime and cement in appropriate proportions, and conducting experiments such as bleeding rate, fluidity, uniaxial compressive strength, X-ray direction (XRD), scanning electron microscopy(SEM), and comprehensively considering flow properties and mechanical properties to obtain suitable coal mines.Filled FA and FGD filling material ratio scheme.The results show that when the ratio of FA, FGD, quicklime and cement is 3:1:1:1, the slurry fluidity of the mineral admixture can reach more than 300 mm and the bleeding rate is 4.71%.The 7 d compressive strength of the backfill is greater than 3 MPa, and the 28 d compressive strength is higher than 4 MPa.With the increase of the ratio of FA and FGD, the 3 d, 7 d strength increases gradually, and the 14 d, 28 d strength increases first and then decreases.The hydration products of FA and FGD filling material mainly include ettringite, hydrated calcium silicate, hydrated calcium aluminum carbonate, and gypsum.The hydration product will fill the pore structure inside the filling body, and the macroscopic performance is to improve the strength of the filling body.