| Converter steel slag contains a large amount of nonhydraulic minerals,which seriously affects the activity of steel slag as a cementitious material.The separation of nonhydraulic minerals in steel slag to improve the activity of steel slag powder that has become the development direction of new technologies.The high activity steel slag powder after separating the nonhydraulic minerals has a lower hydration activity compared with the clinker.In order to explore the technical idea of further improving the hydration activity of steel slag powder,this paper separates the silicate minerals and interstitial phase minerals in steel slag and measures the characteristics of the hydration and exotherm of these two types of minerals.It is intended to find the main factors that restrict the hydration activity of slag powder.In the removal of nonhydraulic minerals in steel slag,the steel slag powder was pneumatically separated to obtain a fine powder with a median diameter of 20 ?m,and the nonhydraulic mineral content was reduced from 33.38% to 15.68%.With wet magnetic separation-wet-grinding-wet magnetic separation,the nonhydraulic mineral content was reduced from 15.68% of the fines to 7.67%.The mechanism of dissolution reaction of cement clinker silicate minerals by salicylic acid methanol(SAM)is studied.Extracting Crystal product which is made from sufficient SAM and cement clinker and then the Monocrystalline is cultured.It is determined by XRD single crystal structure analysis that is calcium salicylate(C14H10O4Ca?2H2O),crystalizes in the monoclinic space group Cc.In the asymmetric unit,Ca coordinates with six carboxylate O from the salicylic acid and two water molecules O,form to an eight-coordinate octahedral structure.The crystal is detected by FTIR spectrum,the peak at 3487cm-1 correspond to the coordinated water molecules,the-OH stretching vibration peak of the carboxyl group at 3519 cm-1 disappeared,and the carbonyl C=O stretching vibration appearing at 1656 cm-1 of the salicylic acid is shifted to lower frequency at 1548 cm-1 of the crystal.In the 13 C NMR spectrum of the crystal,the benzene ring C is substantially unchanged,the C7 is shifted from 171.80 ppm to 176.09 ppm,attributed to the-OH of the carboxyl group is involved in the combination reaction.1H NMR spectrum detected 4.9500 ppm of bound water in the crystal.The results have shown that aluminate and alumino-ferrite are inert phases in SAM.The combination of that carboxyl groups from salicylic acid and Ca O from silicate minerals produces calcium salicylate soluble in methanol.The stoichiometric ratio of salicylic acid to Ca O from silicate minerals is 2.When the stoichiometric ratio is less than 2,the reaction product is different than previous crystal.The reaction product is insoluble in methanol so that the case isn't adopted for clinker mineral separation.Study the selective dissolution of silicate minerals and interstitial phase minerals in steel slag.When salicylic acid-methanol selective dissolution was used to separate the clinker interstitial phase,the influence of salicylic acid content on the reaction was studied.When the separation parameter was clinker: salicylic acid = 1:10,200 m L of methanol solution was used and the reaction was performed at 30°C for 2 hours,Clinker interstitial phase minerals can be isolated.When the clinker silicate phase was selectively dissolved with potassium hydroxide-sucrose,the influence of different reaction time and water amount on the reaction was studied.The separation parameters were: clinker: KOH: sucrose: water = 3g: 10 g: 10 g: 95 m L,95 °C the clinker silicate minerals can be separated by reaction for 5min.When the interstitial phase of steel slag is separated and obtained,the experimental method is the same as that of clinker,and the influence of the study time on the reaction is the same as that of the clinker.When the steel slag silicate phase was isolated,the experimental method was the same as that of clinker.The study time and the effect of sucrose and KOH mass on the reaction were as follows.The separation parameters were steel slag: KOH: sucrose: water = 3g: 12g: 12g: 114 m L,95°C reaction,the steel slag silicate phase can be separated in 10 min.Study the hydration characteristics of mineral phases in steel slag.For the coarse powder and fine powder collected by pneumatic sorting,the cumulative heat release of the steel slag powder 3d and 7d was 90.61 J/g and 109.22 J/g.The cumulative heat release of the coarse powder 3d and 7d was 53.74 J/g and 67.36 J./g,the cumulative heat release of fine powder for 7 days is 1.62 times that of coarse powder.The heat of hydration of pure steel slag powders 3d and 7d was 113.54 J/g and 146.40 J/g,respectively,and the cumulative heat release of reference clinker 3d and 7d was 295.35 J/g and 330.48 J/g respectively.The heat is 38.44% and 44.30% of the clinker's heat release respectively;the exothermic heat of the interstitial phase minerals of the steel slag at 3d and 7d is 57J/g and 89J/g respectively;the interstitial phase of the reference clinker is 3d and 7d and the exotherm is 367.9 J/g,376.7 J/g,the cumulative heat release of the steel slag interstitial phase is 18.45% and 27.38% of the cumulative heat release of the clinker interstitial phase;the cumulative heat release of the slag silicate phase 3 and 7d is 121.3 J/g,159.8 J/g,respectively.The clinker silicate phases 3d and 7d exotherm were 235.9 J/g and 319.8 J/g.The cumulative heat release of the slag silicate phase was 51.4% and 49.9% of the clinker silicate phase,respectively.The reason that the difference in the hydration activity of steel slag is greater than that in clinker is that the activity of interstitial phase minerals of steel slag is far lower than that of clinker.Hydration kinetics model parameters,the slag interstitial phase rate constants K1 = 0.0714,K2 = 0.0039,K3 = 0.0041,are lower than the clinker,and the slag silicate phase due to the presence of f-Ca O,so In K1=0.056 is greater than clinker K1=0.030,the rest of the rate constant K2=0.0068,K3=0.0043 is smaller than clinker. |
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