Preparation Of The Sintered Bricks And Ceramsite With Iron Tailings

Iron tailings refer to a kind of industrial solid wastes generated from the processes of iron ore dressing. With the rapid development of the iron and steel industry, a large amount of iron ore tailings are generated each year. The handling of iron tailings has become a burden of many mining companies. Currently, the iron tailings are mainly reused as raw materials in producing building materials all over the world.This paper deals with the techniques of preparing sintered bricks and lightweight aggregate with the iron tailings as the main raw materials, based on comprehensive analysis of the basic characteristics of the iron tailings. Then, the main properties of the sintered bricks and lightweight aggregate were systematically investigated. The research contents and results of the paper are summarized as the following:1)The characteristics of the iron tailings were systematically studied. The major mineral phases of the iron tailings were quartz (SiO2), clinochlore ((Mg, Fe)6(Si, Al)4O10(OH)8) and calcite (CaCO3) and the minor phases were hematite(Fe2O3) and pyrite(FeS2). But in the iron tailings, the content of the oxide forms of calcium and iron was too high; the content of the oxide forms of silicon was too low. The high Fe2O3 content in iron tailings is due to the presence of clinochlore, pyrite and hematite;the high CaO content in iron tailings is due to the presence of calcite. The presence of the clinochlore maked the iron tailings have good plasticity.2) Sintered bricks were made with the iron tailings as the main materials. The sintering shrinkage, water absorption, apparent porosity, compressive strength of final sintered samples was investigated. Results indicated that adding a little clay or fly ash to the iron tailings played a positive role in reducing the bulk density of the sintered bricks, but the effect of adding fly ash were more obvious. The sintering shrinkage, water absorption and apparent porosity of the bricks with fly ash were 0.5～2%,13～18%,1.8g/cm3～2.0 g/cm3.The compressive strength of the bricks was greater than 15 MPa. The main mineral phases of the product were diopside(Ca(Mg,Al)(Si,Al)2O6), anorthite((Ca,Na)(Si,Al)4O8), hematite (Fe2O3) anhydrite(CaSO4) and quartz(SiO2), which were principally responsible for the mechanical strength of bricks. As shown from the SEM of the samples with fly ash, the microstructures of the fired bricks with fly ash addition were more porous than those of without fly ash.3) The SiO2 content in the iron tailings is lower than the requirements for lightweight aggregates, while the fluxing oxides content in the iron tailings is higher than the requirements for lightweight aggregates. So fly ash and powdery quartz sand were used as additives in this study to adjust the chemical composition of the iron tailings. The bloating index of the samples with 30% iron tailings,10～30% powdery quartz sand and 40～60% fly ash which were sintered at 1210℃ to 1230℃ for 10min to 20min was greater than 1,so all types of LWAs were expanded aggregates. The loose bulk density values were less than 0.8 g/cm3 and the apparent density values were also less than 1.2 g/cm3 in all samples; so all artificial aggregates could be classified as lightweight aggregates. The water absorption of the aggregates was lower, due to the formation of a vitrified external layer in all samples. The main mineral phases of the products were anorthite((Ca,Na)(Si,Al)4Og), quartz(SiO2) and hematite(Fe2O3), which were principally responsible for the mechanical strength of the aggregates. The analysis of microstructures with SEM revealed a vitrified matrix and an extended formation of isolated and closed pores.