| Red mud is a solid waste discharged during the production of alumina,with high alkalinity and complex composition;the accumulation of red mud has caused a lot of waste of land and serious environmental pollution problems.Its treatment and utilization have become a world problem that needs to be solved urgently.Coal-based metakaolin is made from coal-based kaolin,a solid waste discharged during coal production and processing.Geopolymer is a relatively cheap new type of gelling material.It is synthesized by using amorphous aluminosilicate as raw material.Because of its high strength,corrosion resistance,high temperature resistance,low carbon and environmental protection,geopolymer has attracted the attention of many researchers.The geopolymer made from red mud and coal metakaolin,is a new type of geopolymer,which to achieve the purpose of waste treatment,relieve urban development’s demand for cement,be of great significance for solving China’s energy conservation and environmental pollution problems.This paper analyzes the physical and chemical properties of the Bayer process red mud and coal-line metakaolin.After preliminary experiment to get the mixing ratio by selecting suitable alkaline excitation,a red mud-coal metakaolin geopolymer is produced.In order to study the effect of curing age and coal metakaolin contents on its mechanical property,a series of cube compressive strength tests are conducted on red mud-coal metakaolin geopolymer samples with 6 different curing age an 3 different coal metakaolin contents.Additional,its electric resistivity and thermal conductivity are also measured to discuss the relationship of electric resistivity and thermal conductivity with cube compressive strength.In summary,the experiment shows that the alkaline activation solution produced by water glass and sodium hydroxide is an efficient excitant for red mud-coal metakaolin geopolymer,which possesses good mechanical and physical properties.The cube compressive strength of the red mud-coal metakaolin geopolymer increases with the increase of curing age.When age<28d,the strength increases obviously,while,after 28 d,it almost keeps unchanged.At the same age,the strength increases first then decreases with the coal metakaolin content,and reaches the highest value at the content=30%.Meanwhile,the stress-strains curve shows a strain soften pattern,and the elastic modulus of the geopolymer basically remain unchanged when the coal metakaolin content is same.The elastic modulus has a linear relationship with the strength,For red mud-coal metakaolin geopolymer,the elastic resistance is more or less linearly corrected with the compressive strength when the coal metakaolin content≥30%,which implies that the electric resistance measure can be an efficient nondestructive testing method.But,when the content=15%,above rule does not exist.On the other hand,for the same coal metakaolin content,the thermal conductivity is linearly correlated with the compressive strength. |
