Study On Preparation Of New Gelled Material By Using The Ashes After Flue Gas Desulfurization

Geopolymer is a new generation of alumino-silicates inorganic cementitious materials, whose molecular structure consists of [SiO₄]^4- and [AlO₄]^4- tetrahedra linked alternately by sharing all the oxygens. Geopolymer possesses the following merits: upstanding mechanical properties, ultra-excellent durability, and abundant raw materials resources, may make use of industry solid waste in large amount. the semi-dry FGD residues is one kind of solid waste that make flue gas desulfurization in the electric power plant, as compared to Portland cement, alumino-silicates contents are comparatively low in the component, and contain impurity such as biocalc and calcium sulfite, so it is very difficult to utilize the FGD residues as fly ash on construction material. This issue focuses on the preparation of geopolymer utilizing the FGD residues and fly ash as the main raw material, Firstly, it is discussed that the preparation and feature of the geopolymer, we prepared a geopolymer-cement material on this basis and further explored the performance and the mechanism of that.It is analyzed that the composition and structure of raw material, and then ascertained the optimized matching of raw material by the orthogonal experiment, and Constitutes of that is: the FGD residues occupies the solid phase mass ratio is 20%, the leaning kleit is 30%, the sodium hydrate solution occupies the liquid phase mass ratio is 30% and the liquid-solid mass ratio is 2.3. Few calcium oxide and calcium sulfite can promote the aluminosilicate polyreaction, but has the obvious harm to the material congealment speed, the structure, anti-corrosive and thermostble and so on if the content of that is excessive. The X-ray Diffraction, Scanning Electron Microscope and Infrared Spectrum results of the products showed the amorphous substances increases obviously along with polyreaction, calcium oxide and calcium sulfite have not participated in the polyreaction. As a whole the maturing speed of the material is quick, but the development of long-term compressive strength is slow.In order to improve the long-term compressive strength of geopolymer, we prepared a kind of new compound gelled material through matching the cement clinker, the specimen have most superior intensity development relatively in a curing system, that was: First the product solidify one day in the cement standard curing room, solidify six day under the room temperature, then put in the water to raise and test intensity in predetermined time. When the quantity of cement clinker is about 20%, the sodium hydrate solution concentration is about 6 mol/L, the effect that compound the aluminosilicate polyreaction and the cement hydration response is best in the compound system. The complex reaction mechanism is a superimposed reaction that aluminosilicate polyreaction and the cement hydration response supplement and promoted mutually, the main phase of the new compound gelled material have a-SiO₂, mullite, hydration calcium silicate and so on. The se resultants interweave, associate and wraps mutually each other, and forms the three dimensional interlarded structure, which enhanced the density and the mechanical properties of this compound gelled material.