Study On Mechanism And Durability Of Red Mud By Microbial Solidification Bayer Process

With the acceleration of industrialization and urbanization in our country,most aluminum smelters at home and abroad adopt the method of transporting polluting waste to storage yards to deal with the problem of red mud treatment.Microbial solidification of red mud is based on the principle of microbial induced carbonate precipitation(MICP),which makes red mud have certain mechanical properties and weakens its alkaline properties,so that the site can meet the environmental remediation requirements and engineering construction standards.The existing experimental research on soil reinforced by microbial technology is mainly aimed at the sand particle soil with generally large particle size.There are relatively few experimental researches on the small particle size and strong alkaline soil such as red mud.The microbe-induced calcium carbonate precipitation reinforcement technology is the theoretical basis.By changing the concentration of bacteria solution,the concentration of cementing solution,and the number of rounds,the influence of changes in grouting parameters on the reinforcement effect of microbial grouting and solidification of red mud is discussed.In order to improve the reinforcement effect,the use of microorganisms Synergistic reinforcement with calcium hydroxide,and on this basis,by improving the reinforcement method,the pre-mixed bacteria-grouting method is used to further improve the strength and uniformity of the solidified red mud samples;Durability under environment,wet-dry cycle,freeze-thaw cycle.The main research contents and results are as follows:(1)The effect of changing grouting parameters on the reinforcement of calcium carbonate deposition induced by microbial injection of red mud.Microbial reinforcement of Bayer red mud was carried out by grouting method,and the solidified red mud samples with different grouting parameters(bacteria concentration,cement concentration,number of grouting rounds)were compared with those without MICP treatment,it was found that increasing the concentration of bacterial solution,cementing solution and the number of infiltration rounds can effectively improve the compressive strength of Bayer process red mud.(2)The effect of the synergistic effect of microorganisms and calcium hydroxide on the reinforcement effect of red mud samples.The Bayer process red mud was reinforced with microorganisms and calcium hydroxide in different proportions.The results show that the compressive strength of the red mud samples cured by microorganisms and calcium hydroxide is significantly higher than that of the single-acting microorganism-cured red mud samples and calcium hydroxide-cured red mud samples.(3)By improving the reinforcement method,the original grouting method is improved into the reinforcement method of ready-mixed bacteria-grouting.The bacteria and Bayer process red mud were mixed and then grouted for reinforcement.The results showed that the unconfined compressive strength of the sample was significantly improved,and the distribution of calcium carbonate in the upper,middle and lower parts of the sample was more uniform.(4)Disintegration test,dry-wet cycle and freeze-thaw cycle test were performed on the Bayer red mud sample reinforced by ready-mixed bacteria-grouting to study the durability of the sample.The results show that the immersion time,the number of drying and wetting cycles,and the number of freeze-thaw cycles have certain effects on the appearance,mass loss rate and unconfined compressive strength of red mud samples.In the disintegration test,the disintegration rate reached the maximum on the third day and then stabilized with the increase of the number of days;in the freeze-thaw,dry-wet cycle test,with the increase of freeze-thaw,dry-wet times,the strength of the sample decreased.trend.