Effect Of Carbonization On Stability Of Steel Slag

The impact of environmental problems on human beings is increasing day by day,and the frequency of extreme weather is increasing.Protecting the environment is the common responsibility of human beings,and reducing carbon emissions is a key part of it.The mineral composition of steel slag contains C₂S and C₃S,accounting for about 50%of steel slag,so steel slag can be used in cement and concrete fields.However,the f-CaO contained in the steel slag will cause the problem of poor stability of the steel slag,resulting in the cracking of the steel slag cementitious material.In recent years,carbonization has become a new method to solve the poor stability of steel slag.Carbonized steel slag can reduce carbon dioxide emissions,reduce the accumulation of steel slag and strengthen the recycling of steel slag.Furthermore,by carbonization,the f-CaO remaining in the steel slag can be reduced.In this study,the composition of f-CaO in steel slag was simulated.By synthesizing binary and ternary f-CaO in different proportions,the effect of carbonization on f-CaO,as well as the carbonization performance and hydration activity of f-CaO were studied.In the binary f-CaO phase synthesized by simulation,with the increase of the iron element ratio,the CaO-FeO diffraction peak shifts to a large angle,and the excess iron element will precipitate from the CaO-FeO solid solution to form Ca₂Fe₂O₅.The distribution of calcium and oxygen elements is relatively uniform,and the distribution of iron elements is relatively concentrated.The main products of binary f-CaO carbonization are cubic calcite and rod-shaped aragonite,and calcite is more stable than aragonite.With the progress of carbonization,calcite gradually increased and aragonite gradually decreased;and with the increase of iron content,aragonite was more inclined to be formed.As the carbonization progresses,the carbonization degree of the binary f-CaO phase increases,and the generated Ca CO₃ is also more stable.With the increase of iron content,the carbonization degree of binary f-CaO phase decreases,and the generated Ca CO₃ is also more unstable.The highest carbonization rate is above 95%,and the carbonization rate of CaO·0.1FeO phase is the highest,reaching 96.91%.In the simulated ternary f-CaO phase,with the increase of the proportion of iron and the decrease of the proportion of manganese,the diffraction peak of CaO shifts to a large angle,and the excess iron will precipitate from the CaO-FeO-Mn O solid solution.The formation of Ca₂Fe₂O₅ phase,at the same time,more manganese elements will also lead to the precipitation of iron elements,the formation of Ca₂Fe₂O₅ phase.The distribution of calcium,manganese and oxygen is relatively uniform,and the distribution of iron is relatively concentrated.The increase of iron content will lead to a more compact structure of the synthesized ternary f-CaO phase.The main products of ternary f-CaO carbonization are spherical,clustered and rod-shaped aragonite and cubic calcite.With the prolongation of carbonization time,the calcite gradually increased and the aragonite gradually decreased,and the calcite content in the synthesized CaO·0.1FeO·0.1Mn O phase was the highest.With the increase of iron content and the decrease of manganese content,the degree of carbonization decreases,but too much manganese will lead to a decrease in the degree of carbonization.Among them,the carbonization rate of the synthesized CaO·0.1FeO·0.1Mn O phase is the highest,which can reach100%.With the increase of iron content,the hydration activity of binary f-CaO decreases,and the hydration rate of CaO·0.3FeO sample is the lowest,which is 77.01%.The hydration activity of ternary f-CaO decreased with the increase of iron content and the decrease of manganese content.Among them,the hydration rate of the synthesized CaO·0.17FeO·0.03Mn O sample is the highest,which is 88.97%.Carbonization can effectively react the Ca₂Fe₂O₅phase in the binary f-CaO phase and the ternary f-CaO phase,and improve the degree of carbonization.If the carbonization time is too long,the excess CO₂and Ca CO₃ react to form calcium bicarbonate,resulting in carbon loss and a decrease in the carbonization rate.Compared with hydration,carbonization can effectively react f-CaO.In binary f-CaO,carbonization reacts 18.01%more f-CaO than hydration;in ternary f-CaO,carbonization reacts more than hydration.13.77%f-CaO was obtained.