Study On Damage Deterioration And Radon Exhalation Of Uranium Tailings Geopolymer Solidified Body Under Freeze-Thaw Cyclic

The uranium tailings stored in the uranium tailings reservoir is a long-term potential source of radioactive pollution,which is a serious threat to the surrounding ecological security and the health of residents,and the solidification treatment of uranium tailings can effectively control the diffusion of radioactive materials.In this paper,the uranium tailings is taken as the research object.On the basis of literature search and field investigation,sodium hydroxide and sodium silicate were used as alkali activators,metakaolin(MK)and fly ash(F)were added to solidify the uranium tailings,and five kinds of solidified bodies with different ratios are prepared.The damage deterioration and radon evolution of geopolymer solidified body in uranium tailings under six different freeze-thaw cycles were studied by means of laboratory test and theoretical analysis methods.The main contents and conclusions of this paper are as follows:(1)The samples with different freeze-thaw cycles were tested by scanning electron microscope(SEM)and pore structure test.The results show that the SEM diagram of the sample without freeze-thaw is thicker,and after a certain freeze-thaw period,the surface structure becomes loose and the porosity increases.The microstructure of samples55%MK+45%F is relatively dense and the freeze-thaw resistance is better.After a certain freeze-thaw period,the pores of the samples increased,compared with metakaolin,the pore size distribution of metakaolin and fly ash samples were mainly concentrated in the range of micropores and mesopores,and the increase of pore volume of samples 55%MK+45%F was the lowest.(2)The compressive strength and volume resistivity of samples with different freeze-thaw cycles were tested.Studies have shown that with the increase of the freeze-thaw cycle,the compressive strength of the solidified body gradually decreases.After 25 freeze-thaw cycles,the compressive strength of the 55%MK+45%F sample has the smallest drop,which indicates that fly ash can effectively reduce the freeze-thaw damage of the solidified body.In the same freeze-thaw cycle,with the increase of fly ash content,the volume resistivity of the sample gradually decreases,and with the increase of the freeze-thaw cycle,the volume resistivity of the sample gradually rises,and the compressive strength is at the same time.The volume resistivity has a good negative correlation.(3)The cumulative radon concentration of samples with different freeze-thaw periods was measured.The results show that the cumulative radon concentration of 100%MK sample is the lowest without freezing and thawing,and the radon exhalation rate of solidified sample increases gradually with the increase of freeze-thaw cycle,and the radon exhalation rate of 100%MK and 55%MK+45%F samples increases the least after 25 times of freeze-thaw,indicating that metakaolin has a better radon fixation effect.The compressive strength of solidified body has obvious negative correlation with radon exhalation rate,and the bulk resistivity has obvious positive correlation with radon exhalation rate.