Study On The Activation Of Divalent Oxide For Steel Slag And Cementitious Propert

Steel slag is a solid waste,it obtained by cooling the high temperature slag which producted by steelmaking.The reason for this phenomenon is steel slag contain some mineral substance without any cementitious activities and difficult to wear,such as : high iron and about 20% of divalent oxide solid solution?referred as:RO phase?.In this paper,basing on the project of Natural Science Foundation of China "Reaction mechanism on clinker burning chemistry based on in-situ oxidating BOF slag"?number: 21566008?,using the converter steel slag are offered by GangXi LiZou ir on &steel group co.as the research object.In view of the characteristics of substitutional solid solution of RO phase,proposing to add CaO,Al₂O₃ and promote them combine with the RO components under the condition of high temperature,and then form a cemented silicate mineral,which can enhance the slag activity in essence.The research of RO phase separation and silicate mineral re-combination process have carried out.The effects of composition factors such as composition,temperature and mineralizer on the gelation activity of modified steel slag were discussed.Around the above research,the main research work and achievements are as follows:Firstly,the effects of heat treatment on the evolution trend and presence of RO phase in steel slag were investigated by means of TG-DSC and XRD.With the increase of temperature and the prolonging of holding time,the content of RO phase and ferrite phase in molten slag gradually decreases until it disappears.MgO and Fe₂O₃ solution intensified,and the activity of Fe₂O₃ and MgO was higher?the RO phase evolved into Iron and magnesium spinel?MgFe₂O₄?under the condition of air-cooled condition.Furthermore,when the activity of Fe₂O₃ in the slag is higher,it means,while the effective concentration of Fe₂O₃ is higher when it involved in the reaction.Then the effects of CaO and Al₂O₃ on the activation of RO phase and the addition of silicate minerals in steel slag were investigated.XRD and SEM-BEI analysis showed that under the condition of Al₂O₃ content is 3%,CaO content at 10% 25%,with the increase of CaO content,the RO phase disappears and evolved into MgFe₂O₄.which is the transition phase.Then MgFe₂O₄ gradually decreased,C₂ S and C₂ F gradually increased.When the CaO content reached 15%,MgFe₂O₄ disappeared,and gradually appeared free magnesium oxide?f-MgO?,doped CaO has react with SiO2,MgFe₂O₄ respectively.Calcium content of 25% when the limit of the amount of content,converter steel slag appeared in the free calcium oxide.At high temperature,CaO is re-combined with SiO2 and Fe₂O₃ in order of,according to the strength of acidic oxides,the Fe₂O₃ came from RO phase.And then formation of silicate minerals and ferrite minerals.Finally,adding the mineralizer to the reconstructed steel slag to stabilize the MgO phase which separated from RO phase.The experimental results show that the mineralizer can promote the encapsulation of f-MgO,but it worked weak and can not digest all f-MgO.Gypsum promoting effect is better than phosphorus pentoxide.CaSO4 not only contributes to the activation and solid solution of MgO in steel slag,but also improves the gelation activity of steel slag.When the CaO and CaSO4 contents were 15% and 3%,the hydration heat of steel slag increased by 2.78 times,and the intensity of 3d and 28 d increased by 28% and 4.6%,respectively.The overall study shows that,Regulators and mineralizers can effectively activate the RO phase,improve the total amount of steel slag hydration and mechanical properties,ensure the stability of steel slag mixture.Which has laid a foundation for the wide application of steel slag with high value-added.