| Tailings as a solid waste produced by mining engineering have a low utilization rate and are mainly treated by piling and landfill,which leads to a large amount of resources waste and serious safety risks.With the improvement of environmental protection requirements in China,the resource utilization of tailings has gradually become a research hotspot.The application of tailings in building materials can not only produce products that meet the requirements of the regulations and produce certain economic benefits,but also eliminate tailings waste on a large scale and realize the utilization of tailings resources with high added value.In this dissertation,with vanadium-titanium iron tailings from Chengde area as the main raw material,the high strength permeable brick supplemented by other tailings waste successfully prepared to achieve the requirements of the specification.The main contents are the research on the characteristics of vanadium-titanium iron tailings,the preparation of high-strength permeable brick of vanadium-titanium iron tailings,the sintering mechanism of high-strength permeable brick of vanadium-titanium iron tailings,and the economic analysis of high-strength permeable brick project of vanadium-titanium iron tailings.The main conclusions are as follows.Through the study on the characteristics of vanadia-titanium iron ore tailings,it is found that the particle size is fine,with the grain size mainly between 0.30～1.18mm,the chemical compositions are mainly Si O2,Ca O,Fe2O3,Mg O,Al2O3,and the main mineral compositions are diopside,chlorite,mica,etc.,The appearance of the color gradually deepened at different sintering temperatures,while the mineral phase changes,mainly generated orthoclase,akermanite,diopside,augite.The high strength permeable brick made from vanadium-titanium iron tailings has a compressive strength of 64 MPa,a permeability coefficient of 0.062cm/s,and a water retention of 0.62 g/cm2,which meets the requirements of the specifications GB/T25993-2010 Permeable Pavement Bricks and Permeable Pavement Plates and JCT945-2005-Permeable Bricks,and the comprehensive utilization rate of tailings reaches 80%.In the study of the aggregate grading and binder ratio of permeable brick,it is found that the best aggregate grading is 1.18～4.75 mm 20%,0.60～1.18 mm 50%,0.15～0.60 mm 30%,the best binder ratio is gold tailings:shale:clay 2:1:1,in which the aggregate content is 78%,the binder content is 22%.The optimal sintering system are as follows:Room temperature～60℃（0.5℃/min）,60～300℃（2℃/min）,300℃ constant temperature for 60 min,300～800℃（3℃/min）,800℃ constant temperature for 60 min,800～1080℃（1℃/min）,1080℃ constant temperature for 90min,along with the furnace to room temperature.The sintering mechanism of XRD,SEM and EDS was studied that the ternary system mainly composed of Mg O-Ca O-Si O2 is formed during the sintering process of permeable brick.The Mg O,Ca O and active Si O2 react to form diopside,and the diopside is converted to augite by combining with Fe3+and Al3+in molten liquid phase.The pyroxene phase crystals are small and short columnar,which is conducive to the mutual filling of crystals in the system and the formation of grid structure,to improve the structure compactness.The investment profit rate of high-strength permeable brick project of vanadium titanium iron tailings is 65.3%and the investment profit rate is78.3%.When the production reaches 48.585%of the designed output,there will be no loss,so it has a strong risk resistance ability. |
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