Study On Preparation Of Ready-mixed Concrete From Vanadium-titanium Iron Ore Tailings As Minerals Admixture

In this paper,vanadium-titanium iron ore tailings were studied.Laser particle size meter,XRD,XRF,SEM and other technical methods were used,the mechanical and chemical activation mechanism of preparing tailings from the perspective of characteristics of vanadium-titanium iron ore tailings.The mechanical-chemical activation mechanism of tailings for preparation of tailings micro-powder was proposed from the point of view of characteristics of vanadium-titanium iron ore tailings.The influence law of tailings used as mineral admixture in concrete was studied systematically and comprehensively,and the application technology of tailings micro-powder in concrete was put forward.The application of tailings micro-powder from laboratory to engineering has been realized.Firstly,the mechanical activation method was used to prepare the tailings micro-powder.The particle size distribution,uniformity and morphology of the tailings micro-powder were analyzed,and the mineral characteristics and activation law of the tailings were explored.Secondly,the activation of vanadium-titanium iron ore tailings was compared with that of slag powder and fly ash,and the hydration mechanism of cementitious materials of vanadium-titanium iron ore tailings micro-powder was analyzed to study the hydration process,hydration products and hydration rate.Finally,C30 ready-mixed concrete with durability and working performance conforming to the national standard was prepared by using vanadium-titanium iron ore tailings cementitious materials.Based on the above research,the following conclusions were drawn.The analysis of the characteristics of vanadium-titanium iron ore tailings showed that the main mineral compositions were amphibole and diopside,and the minor mineral components were plagioclase,chlorite,mica and ilmenite.The content of silicon and aluminium was low.The best effect of the cementitious materials was prepared by mechanical activation of vanadium-titanium iron ore tailings micro-powder for 40 minutes,and the specific surface area of the micro-powder was400m²/kg.Under the same conditions,the fluidity of mortar mixed with tailings micro-powder compared with the slag had little effect,but it was better than that mixed with fly ash.The amount of vanadium-titanium iron ore tailings micro-powder in cementitious materials should not exceed 30%.The mechanical properties of mortar block could be greatly reduced by mixed tailings micro-powder alone,and the working properties of mortar block could be reduced when compound mixed.Through XRD,SEM,hydration heat analysis and other testing methods,the hydration mechanism of composite cementite was studied.It was found that the hydration degree of cementite decreased when the content of tailings was increased in the hydration reaction system of tailing-cement system.With the increase of curing age,the hydration product and C-S-H gel of tailing cement system in 28d increases,the amount of Ca?OH?₂ decrease.Quartz and diopside minerals remain in the system,this implies,a small amount of silicon aluminium mineral was activated in under the action of mechanical force chemistry,in can play an secondary hydration reaction of gelled material system,tail kuangfen in system also have the effect of optimization of grain size distribution and filled with dense.The concrete prepared with vanadium-titanium iron ore tailings micro-powder had good overall performance.When the maximum mixed content of tailings micro-powder was 16%of cementitious materials,the 3d and 28d compressive strength of C30 Ready-mixed concrete prepared by tailings micro-powder were13.4MPa and 40.3MPa respectively,and the working performance was good.It was found that the mixing of tailings greatly improved the freeze-thaw resistance of concrete,the number of freeze-thaw cycles was 125,while the number of freeze-thaw cycles of ordinary concrete was 25.The shrinkage rate of tailings concrete was slightly0.0084%than ordinary concrete.