The Effect Of Fluoride And Sulphate Mineralisers On High C₃S Cement Clinker Formation

This paper emphasizes on the study of the using of fluoride and sulphate mineralisers to improve the burnability of high C₃S cement raw meal. MM, XRD, DTA, HTM,SEM and EDAX are used to study the role of fluoride and sulphate in high C₃S cement clinker formation and the effect on C₃S crystallization. The results show that fluoride-sulphate composite mineraliser improves the burnability obviously, and CaF₂ helps burning only in lower temperature and phosphogysum shows no evident effect on the formation of clinker in which alite is eroded by liquid phase decompounded by the intermediate compound. Adding of mineralisers can accelerate carbonate decomposition, and especially when fluoride-sulphate composite mineraliser added, 44℃is reduced for the height peak temperature of carbonate decomposition. Mineralisers can change the property of liquid phase, such the fall of liquid phase appearance, the increase of liquid phase amount, reduction of liquid phase viscosity, and so on, which creates good condition for C₃S formation. When fluoride-sulphate composite mineraliser is added, the temperature of liquid phase appearance is 140℃earlier than blank raw meal, and the temperature of mass liquid phase appearance also becomes earlier. The decomposition of intermediate compound causes C₃S formation, which has the effect of crystal nucleus and makes its growth early. The effect of 3C₂S·3CaSO₄·CaF₂ is greatly obvious, whose fusing generates liquid phase, promotes C₃S formation, and make clinker burned at about 1300℃. Fluoride mainly dissolves in the alite, secondly in belite, and the least in the interstitial phase. Volatilization at high temperature and solid solution in silicate phase make the fluoride left too little to form C₁₁A₇·CaF₂. That fluoride and sulphate enter alite doesn't change its polymorphism, and just forms solid solution。...