Experimental Study On Mechanical And Chemical Effect Of Siliceous Iron Tailings

The main mineral composition of siliceous iron tailings is quartz,the main chemical composition is SiO2,and the content of SiO2 is 78.96%;The tailing is grayish brown with irregular particle shape,and the particle size is mainly concentrated in 50-150 μm.The effect of mechanochemical activation on the physicochemical properties and crystal structure of siliceous iron tailings was studied.This study has theoretical significance for the application of siliceous iron tailings as auxiliary cementitious materials in cement-based materials.According to the D50 and D90 of iron tailings particles,the grinding system was established as follows:rotating speed 360r/min,ball material ratio 3.75:1 and average ball diameter 8.70mm.Under the action of mechanical force,the particle size,specific surface area,density and solubility of siliceous iron tailings change.The results show that:in the initial stage of grinding,with the increase of grinding time,the particle size of tailings decreases,the specific surface area increases,the density decreases,and the solubility increases;At a certain grinding stage,with the increase of grinding time,the particle size of tailings increases,the specific surface area decreases,the density increases and the solubility decreases.The results of SEM,XRD,FT-IR and DSC-TG show that after mechanical grinding,the diffraction peak intensity of main mineral crystal plane of iron tailing powder decreases,the half peak width increases,the crystallinity decreases,the microstrain increases,the grain size decreases and the effective temperature coefficient increases,which indicates that the crystal structure of quartz in siliceous iron tailing powder is changed and transformed to amorphous state by mechanical chemical action;The results show that the symmetry and integrity of mineral crystals in iron tailing powder are changed by mechanochemical action;The exothermic peak on the DTA curve gradually moves to the low temperature direction,and the change of iron tailing powder quality increases with the increase of grinding time when the temperature increases,which indicates that the chemical reaction degree of iron tailing powder increases due to mechanochemical action;SEM shows that the morphology of iron tailings is changed by mechanochemical action.The performance test of cement iron tailings composite cementitious material shows that when the content of mechanochemically activated siliceous iron tailings is below 40%,the standard consistency water consumption of composite cementitious material increases with the increase of iron tailings content;The stability,initial setting time and final setting time of composite cementitious materials meet the requirements;The 28d compressive strength ratio of composite mortar increases from 55.7%to 86.4%,so the activity of siliceous iron tailings increases due to mechanochemical action.Based on the variation of particle size and specific surface area of iron tailings in grinding process,the grinding limit is determined to be 3.5H.At this time,the solubility changes also reach the limit,and the density,crystal diffraction peak intensity,half peak width,grain size,microstrain and effective temperature coefficient are close to the limit,while the crystallinity and thermogravimetric loss do not reach the limit.