Microstructural And Mechanical Features Of Porcelain Brick Prepared From Coal Gangue

The recycling utilization of solid wastes is an important issue of sustainable development nowadays. Coal gangue (CG) is the main solid wastes generated in coal industry, which is the largest amount of both yearly discharged and accumulated pile industrial solid waste in China. The CG occupies a great deal of land, but also pollutes the water, soil and atmosphere. Therefore, it results in the elimination of CG pollution, and on the other hand it contributes to a decrease in the consumption of clay minerals, if the CG could substitute the clay to prepare porcelain tiles.Coal gangue porcelain brick (CGPB ) is a kind of porcelain tiles that is prepared from coal gangue as main raw material. The CG samples used in this paper came from FengFeng diggings in HanDan city, HeBei province, which is composed of 64% kaolin, 20% illite, 12% quartz, 2% chlorite and 2% calcite. In the experiments, the content of the CG in the mix-designs can reach up to 80%, and the bending strength of the porcelain body fired at 1220℃ is beyond 35MPa. Moreover, the optimal mix-design is the one containing 60% CG, and the bending strength and water absorption of its porcelain body fired at 1190℃ can reach 68.4MPa and 0.21% respectively.The quartz, mullite and amorphous phase can be observed in the CGPB by X-ray diffraction analysis (XRD) , which is similar to the traditional porcelain tiles (TPT) . But the content of quartz in the CGPB is less than in the TPT, and the content of mullite in the CGPB is more.Scanning electron microscope (SEM) micrographs show that two kinds of pores can be observed in the vitreous phase of porcelain bodies. One is the micro-pore with the diameter approximately in the range of 2-10μm, which is from the release of gas from the chemical reaction between Fe₂O₃ and C. By contrasting with the TPT, the porosity of micro-pore in the CGPB is higher. Another is the big pore with the diameter exceeding 10μm, which comes from the agglomeration and non-uniform pileup of the batch particles. This big pore becomes one kind of flaws of the CGPB. The main crystal in the CGPB bodies is quartz with the diameter between...