Soundness And Hydration Activity Of Steel Slag Based On Carbonation

In steelmaking process,a lot of steel slag is produced with more CO2.Because of its hydration activity,steel slag can be used as cement mixtures in building materials,but its soundness has hidden dangers.Utilizing carbonation curing,CO2 can be captured and stored,meanwhile the poor soundness of steel slag can be ameliorated,which guarantees for its wide application.In this paper,the hydration reactivity and soundness of different composition and fineness steel slag were studied.In addition,the affecting factors of hydration reactivity and soundness were explorated.Main research achievements and conclusions are as follows:1?The composition and fineness of steel slag had an outstanding effect on its soundness.Owing to larger volatility of composition,the contents of calcium and magnesium showed obvious difference between different steel slag.And the higher contents of calcium and magnesium,the poorer soundness of steel slag.Nevertheless,grinding time can significantly increase the fineness of steel slag,decrease the expansion ratio of steel slag products,and then improve the soundness of steel slag.The experiment indicates that the fineness of steel slag could not increase furtherly,whereas the expansion rate of products could decrease continuously.2?According to carbonation curing,C2S,C3S,CaO and Ca?OH?2 could be consumed,and calcium carbonate was generated.As a result,the hydration reactivity of steel slag decreased due to the consumption of C2S,C3S.The experiment suggests that the content of water and the carbonation curing time had a slight influence on the hydration reactivity of steel slag.3?The fineness and the degree of carbonation reaction can affect the stability of steel slag.With prolonging carbonation curing time,the specimens showed a better volumetric stability.Besides,larger fineness steel slag showed minor expansion rate,indicating better volumetric stability.In other words,the larger specific surface area and the longer carbonate curing time,the better volumetric stability of steel slag products.In addition,increasing the specific surface area of steel slag can enhance its stability,even if the degree of carbonation is low.In other words,increasing the degree of carbonation of steel slag also can improve stability of steel slag,even if a smaller specific surface area.After 20 minutes of carbonation curing,the steel slag with a specific surface area of 483.58 m²/kg was stability qualified,and the contents of calcium carbonate in steel slag was 23.4%.After 10 minutes of carbonation curing,the steel slag with a specific surface area of 531.66 m²/kg kept stability qualified,and the contents of calcium carbonate in steel slag are 21.6%.4?Quantitative analysis by QXRD found the f-MgO in the steel slag was consumed by carbonation curing,and the products of carbonation were mainly CaxMg1-xCO3.CaxMg1-x CO3was formed during the precipitation of Mg²⁺into CaCO3,and its diffraction peak overlapped with that of calcite.Magnesium hydroxide?MH?was not found in the autoclave sample.5?The hydration reaction of overburning CaO:the hydration activity of CaO could be reduce through prolonging constant temperature time in firing process of CaO.Fe,Fe with Al both could restrain the hydration reaction.And,grain size of CH grew up with hydrating of CaO,especially in 10-20 minutes.Meanwhile,the bulk CH crystal were formed by stacking each other.In addition,Al could accelerate the growth of CH crystal,even if could not affect the hydration reaction of CaO.