Mineral Composition Characteristics And Reaction Kinetics Simulation Of High Alite White Portland Cement Clinker

High-grade white Portland cement（WPC）has been widely used in modern building decoration engineering,but the theoretical research on high-grade WPC is still in a blank state in China.The traditional technology and theory have been unable to meet the requirements of the development of modern WPC.It is of great practical significance to break through the shackles of the traditional theory and reconstruct the theoretical system of WPC under the condition of new technology.XRD-Rietveld,SEM-EDS,TG-DSC and hydration calorimetry were used to study the effects of calcination conditions on the mineral composition and crystallization characteristics of WPC.The effects of fluorine and phosphorus doping on the burnability of WPC,the mineral composition of the clinker and the evolution of crystal form were studied.High Alite WPC clinker was prepared by mineralizer doping and suitable calcination system,and its mineral composition and mechanical properties were studied.The reaction force field method was used to simulate the dynamic mechanism of solid reaction in WPC sintering process.The following conclusions were drawn:（1）Both the calcination temperature and the sintering time will significantly change the C₃S crystal form in the white Portland cement clinker.As the temperature increases,the crystal form of C₃S changes from T3 to M1 and M3.As the sintering time increases,the C₃S crystal form changes from T3 with poor symmetry to M and R with good symmetry.Increasing the sintering temperature and prolonging the sintering time can reduce the f-Ca O and C₂S in the clinker and increase the C₃S grain size.（2）When the content of CaF₂ is 0.5～1.0%,it can promote the formation of tricalcium silicate and make the C₃S crystal transform to the more active M-type crystal form.However,excessive CaF₂ will cause the liquid content in the clinker to be too high,and the temperature control interval will be narrowed.1.0%calcium fluoride improves the hydration activity of cement minerals most obviously,and excessive fluorine content is unfavorable to the hydration activity of cement.（3）The content of P₂O₅ within 1.0%can promote the calcination of WPC clinker and increase the content of C₃S.The micro-mineral morphology of WPC clinker calcined with 0.5%Ca₃（PO₄）₂ is the clearest,and the boundary is relatively straight.Higher than 1.0%P₂O₅ will inhibit the formation of C₃S crystals,but can stabilize high-activity C₂S crystals.（4）Fluorite and phosphate tailings have a burning-promoting effect on the high alite white Portland cement raw meal.Fluorite and phosphate tailings are selected as high alite white cement mineralizers,and the optimum dosages are 1%and 2.5%,respectively.Fluorite can promote the development of the system in a direction that is conducive to the nucleation and growth of tricalcium silicate,so that the crystal nucleation-growth speed is significantly improved.（5）During the sintering process of high alite white Portland cement clinker,the distribution of calcium atoms affects the entire reaction process,and the directional movement of calcium ions is likely to come from the nucleation of tricalcium silicate.It is speculated that the nucleation rate of tricalcium silicate controls the solid-phase reaction rate of the entire clinker sintering process.