Mechanism Of Iron Tailings Powder In Cement-based Materials

The output of iron ore increases with the development of modernization,and the amount of iron ore tailing?IOTs?in China has reached nearly 6 billion tons a year.IOTs not only occupy a large number of agricultural and forest land but also pollute the environment.Fortunately,IOTs can play an important role in many fields with further investigation,such as building materials industry.In order to make a comprehensive understanding of the application of IOTs on concrete,a series of studies are carried out in this paper.The main content is as follows:?1?Iron tailing powder is used as fine aggregate to replace part of sand,the fluidity and water-retaining property of mortar is reduced and enhanced respectively,while the strength of mortar shows peak characteristics.When iron tailing powder displaces 8%of sand,the pores between sand grains can be filled by fine iron tailing powder particles,resulting in higher initial density and lower porosity of the mortar,The compressive strength of the mortar reaches its maximum value.While the breaking strength of mortar is the maximum when 15%of sand is replaced by iron tailing powder.?2?Iron tailing powder can replace part of cement as admixture,and with the increase of amount of iron tailing powder the net slurry fluidity increases and the water retention property weak.While Adding fly ash weakens the fluidity and enhance water retention of motar.?3?adding the appropriate amount of iron tailing powder can enhance the strength of the motar.However,too much IOTs in motar makes hydration process of cement insufficient,leading to increase of porosity and declines of strength of cement paste.?4?Whether mixed with fly ash and the particle size of IOTs affect the strength of cement paste.When the fly ash and IOTs powder are mixed and the dosage is 15%,the strength of the cement paste is relatively high.The strength of the cement paste is higher after adding the IOTs powder with good particle size grade.?5?The activity of IOTs is tested by compressive strength and activity index.The results showed that finer IOTs has better activity,and the activity of IOTs powder is worse than that of fly ash.?6?hydrodynamic results show that:the density and strength of specimen reache a top because of the filling effect of IOTs powder when IOTs powder replaces less than 8%of sand and accounts for no more than 15%of all admixture.While the water absorption capacity and the average pore diameter of the specimen are greatly reduced.?7?XRD results show that the amount of Ca?OH?₂ in the specimen increases because the addition of IOTs powder can promote cement hydration in the early stage.The alumina in the IOTs powder reacts with Ca?OH₂?to form calcium aluminate.In summary,the iron tailings powder has certain activity and can be used as a blending material in concrete,but its content is not more than 15%,and it can be mixed with fly ash in practical applications.