Preparation And Study On Performance Of Fly Ash Red Mud Porous Ceramics

Fly ash and red mud discharged by industry pollute the environment seriously. It is a difficulty for us to utilize fully utilize these mineral waste residue. In this paper, the fly ash and the red mud were used to prepare the high void volume and high strength porous ceramics by adding pore-forming agent, with the help of pore-forming agent, which explored a new way to comprehensive utilization of fly ash and red mud.The effects of content ratios of two kinds of raw materials, pore-making agent, firing temperature, holding time and additive quantity on the apparent porosity, flexural strength, water absorption, linear shrinkage, bulk density, microstructure and physical were studied.The result show that the porosity of porous ceramic materials is influenced by the content ratio of two raw material, pore-forming agent and sintering system; The additive quantity and the sintering temperature affect the flexural strength greatly. The moderate increase of red mud is benefit to the strength and porosity, however, an excess of red mud can cause the linear shrinkage of samples. With the increase of pore-making agent, the porosity and water absorption of the sample increase while the flexural strength and volume density decrease. Higher the sintering temperature is, more dense the sample structure is, smaller the porosity and water absorption are and higher the flexural strength and bulk density. Bentonite is good to the plasticity and intensity of the sample, but is bad to the porosity. Borax is not only benefit to reduce the sintering temperature, but also to improve the sample strength significantly, under overall consideration, the proportion of fly ash and red mud should be control in3/1～2/1, sintering temperature in1125℃～1150℃, pore-forming agent in15%-25%, bentonite addition amount in2%-4%, borax addition amount in2%～3%. When fly ash to red mud is2/1and fire at1150℃, the apparent porosity of the prepared sample is48.33%, flexural strength is16.5Mpa; bulk density is1.28g/cm3, linear shrinkage is4.75%. The comprehensive utilization of fly ash and red mud reached76%. XRD analysis of porous ceramics showed that the main phases in porous ceramics is Al2SiO5, Fe2O3,[Ca,Na][Al,Si]2Si2O5, Ca2Fc2(SiO4)2. There were more Fe2O3in the samples when using red mud rich in Fe2O3. The firing temperature has no significantly affect on the formation of crystalling phase of porous ceramics. SEM analysis indicates that there is a great quantity of three-dimensional pores whose diameters were about5μm-40μm. The inner surface of these porous is sags and crests which has high specific area.