Preparation And Properties Of Geopolymer Based On Anshan Iron Ore Tailings With High Silica

Iron tailings are one of the largest solid wastes in China in terms of stockpiles and emissions,and the comprehensive utilization rate of iron tailings in China is less than 20%at present,and the stockpiles and landfills of tailings have caused great pressure on the environment.In this paper,the geopolymer was prepared from high-silica type iron tailings of Anshan and silica-alumina corrected materials of metakaolin and fly ash.Different experimental schemes were selected for the iron tailings geopolymer mixed with different materials;the reaction mechanism was determined by microscopic analysis（XRD,SEM,FTIR）;the work performance and durability performance of the prepared geopolymer were tested,and the main research results are as follows.（1）The reactivity of iron tailings is low,and the addition of higher activity of metakaolin can make the geopolymer prepared at room temperature;for the iron tailings-metakaolin base polymer,the increase of exciter modulus will affect the early strength characteristics of the geopolymer;however,for the high modulus alkali exciter,the increase of sodium silicate concentration will improve the compressive strength of the specimen after 28d.The optimum ratio of 20%mass fraction of iron tailings,45%concentration of sodium silicate solution,and modulus 1.4 of modified water glass is obtained by orthogonal test with extreme difference analysis and ANOVA,and the compressive strength at 28 d is 45.5 MPa and flexural strength is 5.1 MPa.（2）Other activation means are needed to improve the strength when iron tailings are added with less active fly ash,and high temperature water curing can significantly improve the strength of ground aggregates.The analysis is carried out by response surface method,and the main order of influencing factors affecting the strength is obtained as follows:curing temperature>iron tailings admixture>liquid-solid ratio,and the best ratio is 19.67%mass fraction of iron tailings,0.5 liquid-solid ratio,water curing curing temperature of 72.33℃,compressive strength of 37.89MPa and flexural strength of 4.7MPa at 28d.（3）The reaction process of geopolymer is studied by microscopic analysis of raw materials and specimens with representative ratios;the changes occurring before and after the reaction of geopolymer are compared to prove the degree of reaction of geopolymer and verify the change of strength under different ratios.（4）Single-factor experiments are used to measure the setting time and flowability of iron tailings-based aggregates,and the results showed that iron tailings can retard the setting time but have a small effect on the flowability.The results of the freezing and chemical corrosion resistance tests on the iron tailing-based aggregates in the best ratio showed that the specimen surface of the iron tailing-based aggregates is blocky and spalling during the freeze-thaw cycles,and the mass loss would increase abruptly,and the strength loss rate is greater than 5%when the iron tailing-metakaolin-based aggregates are freeze-thaw cycled 75 times and the iron tailing-fly ash-based aggregates are freeze-thaw cycled 125 times.The greatest strength loss is observed for iron tailings-based aggregates immersed in H₂SO₄ solution.