Preparation And Properties Of Low-silicon Iron Tailings Geopolymer

Geopolymer as a new type of green inorganic cementitious material has been developed in recent years,with the good mechanical properties and durability.Generally,geopolymer is prepared with metakaolin,fly ash,slag and other high content of active silicon and aluminum industrial wastes as the main materials,under the action of an alkali activation.In order to realize the secondary resource utilization of low-silicon iron tailings,low-silicon iron tailings is used as the raw material in this study,and a small amount of metakaolin is added to prepare the geopolymer.The optimum preparation process parameters of low-silicon iron tailings geopolymer were studied.Then by activating low-silicon tailings to improve the performance of the geopolymer.Micro-analysis and durability of geopolymer were studied.The results are as follows:?1?Preparation and characterization of low-silicon iron tailings geopolymerThe study found that under the optimal formula ratio with silicon to aluminum ratio[n?SiO₂?/n?Al₂O₃?]of 2.75,liquid-solid ratio of 0.3,the alkali activator modulus of 1.4,with the process conditions of pressing forming and cured at room temperature in sealing bag,the compressive strength of the prepared geopolymers 3d,7d and 28d were55.6MPa?68.0MPa?72.3MPa respectively.And the microscopic analysis showed that there were a large number of amorphous N-A-S-H gel phase and C-S-H gel phase in the sample,which closely bond various mineral crystals together and filled the pores of the particles to form a compact internal structure.?2?Preparation and characterization of activated low-silicon iron tailings geopol ymerBy testing the compressive strength of geopolymer,the effects of different activators and activation methods on geopolymers were investigated,The results showed that NaOH was the optimal activation agent,the ratio of low-silicon iron tailings to NaOH was 1:0.45 by weight,the optimal activation method was to wet mix firstly,then calcinate at 600?and cool at quenching heat,under this activation condition,the compressive strength of the prepared geopolymer of 7d was 82MPa.And the microscopic analysis showed that the quartz,mullite and kaolinite phases in the prepared geopolymer after activation were reduced,and more dense gel phases were formed,the structure was denser and the pores were smaller,this showed that the activation of low-silicon iron tailings promoted the cleavage of Si-O bond and Al-O bond in low-silicon iron tailings and the dissolution of most of the active silicon-aluminum components in low-silicon iron tailings.more better gelation polymerized products were formed,which enhanced the sample's mechanical properties.?3?Study on durability of activated low-silicon iron tailings geopolymerDurability of geopolymer prepared under the optimal activation process parameters was tested,the results showed that the mass loss rate of the geopolymer in HCl and H₂SO₄ solutions was 4.6%and 4.0%,respectively,the mass loss rate of the geopolymer at a high temperature of 800?was 1.2%,the geopolymer had good chemical corrosion resistance and high temperature resistance compared with ordinary Portland cement.However,after 30 freeze-thaw cycles,the surface of geopolymer had large-area cracks,the mass loss rate of the geopolymer was 5.8%,the geopolymer had poor freeze resistance compared with ordinary Portland cement.Overall,The geopolymer has good chemical resistance and high temperature resistance properties.This study has demonstrated that the reuse of low-silicon iron tailings to prepare geopolymer is an effective way to achieve resource utilization.The proper curing conditions optimization and active excitation can further improve the performance of the geopolymer,and the prepared geopolymers have high early strength and good durability.