Preparation Of Alumimate Cement CA50 By Using Aluminum Ash To Partly Replace High-grade Bauxite

Calcium aluminate cement is used as the refractory castings and high temperature adhesives in refractory because of the outstanding properties compared to Portland cement,such as fast hard,high early and later strength,high temperature resistance and fluid erosion resistance and thermal shock resistance.One of the main raw materials of the calcium aluminate cement is bauxite?the content of Al₂O₃ in which is demanded to be more than 73.5%?.However,the reserves of bauxite in china is shortage,especially the high quality bauxite which satisfy the standard of calcium aluminate cement is shortage more.That is the main reasons of the high cost of calcium aluminate cement.Alternative raw material for high grade bauxite is the key point to achieve the sustainable development of calcium aluminate cement.Aluminum ash is a kind of waste discharged in a firstly and secondary aluminium industry,which constituted with aluminum,aluminum oxide,aluminum nitride and carbide,etc.At present,million tons of domestic aluminum ash were discarded or landfill per year,which polluted the environment and wasted aluminum resources.Aluminum ash has been used to replace bauxite to produce sulphoaluminate cement because of the high content of Al₂O₃.And it might also be used as Al₂O₃ sources to produce calcium aluminate cement.But it is limited to used in summer because of the phenomenon that the setting time is short.In this study,the effect of aluminum ash on preparation,minerals,structures and properties of calcium aluminate cement has been researched.Results showed that parts of high-grade bauxite could be replaced by aluminum ash in preparation of calcium aluminate cement CA50 clinker because of the similarity of the two raw materials in chemical compositions.The performance of prepared calcium aluminate cement CA50clinker could meet the national standard GB/T 201-2015 when 5.50%of high-grade bauxite were replaced by aluminum ash.Burnability of raw materials could be improved by adding of aluminum ash or boiled aluminum ash,which would reduce the energy consumption in production of calcium aluminate cement.The addition of aluminum ash would inhibit the formation of CA mineral in clinker,but increase the content of mineral CA₂ with decreased crystal size.When the replace content of aluminum ash was less than 5.50%,it has little effect on mechanical properties and its development of clinker,mainly 6h strength is slightly lower.However,the performance of prepared clinker could not meet aluminate cement CA50 requirement when much more aluminum ashs were added.Under this experimental condition,the largest mixing ratio of aluminum ash is 5.50%while the clinker meets the requirements of CA50.The addition of boiled aluminum ash has less effect on the formation of CA and CA₂.And the crystals size of CA₂ would increase.Water requirement according to the standard consistency of calcium aluminate cement increased with the increase of aluminum ash and boiling aluminum ash,which would increase the water-cement ratio and therefore decrease the mechanical properties.Research results also showed that the utilization of aluminum ash in aluminate cement could reduce the use of high-grade bauxite and the production cost.However,the preparation of calcium aluminum cement with aluminate ash is needed to be further studied.