Study On Multi-solid Waste Coupling Activation And Properties Of High Silicon Iron Tailings

In recent years,the vigorous development of Chinese industry has brought a large number of solid waste generation and accumulation,which led to a series of security,environmental and other issues.The incorporation of industrial waste residue into concrete as an admixture is a common way of solid waste recycling,but the supply of high-quality admixtures such as FA and GGBFS have been in short supply.IOTs are industrial solid wastes with large production,low utilization and high environmental pollution in China.Due to the large amount of Si O₂contained in its chemical composition,IOTs have the potential to be developed into concrete admixtures.Si O₂ in IOTs are mostly crystal structure,which are difficult to exert volcanic ash activity,so it must be activated.In this thesis,the mechanical-chemical coupling activation method was used to stimulate the activity of IOTs.The particle characteristics and microstructure changes of IOTs were explored by XRD,XPS,SEM and BET methods to reveal the source of IOTs gel activity and find out the optimal coupling activation parameters under the excitation of IOTs gel activity.The ternary admixture system was developed by synergistic development of IOTs and other two kinds of industrial solid wastes rich in calcium oxide and alumina,and the influence of different parameters on the activity index of the ternary system was analyzed to reveal the hydration and hardening mechanism.The experimental results show that:（1）After mechanical-chemical coupling activation,iron tailings can increase specific surface area,improve particle gradation,and reduce crystallinity and surface binding energy.When activated iron tailings are used as admixture,the activity index is improved by excellent filling effect and a small amount of secondary hydration.Moreover,the effect of mechanical-chemical coupling activation is better than that of single mechanical activation.When the single component of activated iron tailings is used as concrete admixture,the activity index of 28 days can reach up to 79.84%,which cannot meet the use standard of grade I concrete admixture.（2）In IFG ternary system:The activity index of 28 days was up to 98.47%.The proportion of IOTs in the ternary system was the optimal between 33%and 20%.the optimal ratio of FA to GGBFS is 1:1 and 3:2.TG test confirmed that the secondary hydration reaction consumed CH.SEM test confirmed the existence of filling effect.There are more C-S-H gels in the later stage of hydration,which further confirms the secondary hydration reaction.Porosity and gel pores increased,capillary pores,pores decreased,the most probable pore size changed little,reducing the connectivity of the pores,pore structure distribution more uniform.（3）In ICS ternary system:The activity index of 28 days was up to 88.29%.In the ternary system,the proportion of IOTs are the optimal between 33%and 20%.the optimum ratio of CP and SS is 1:2 and 1:1.ICS system generates more ettringite particles in the early hydration stage,which reduces the C-S-H gel content.The content of C-S-H gel is higher in the later hydration period.The total porosity is high,the gel pores and capillary pores are increased,and the most probable pore size is increased.The coarse steel slag particles lead to poor particle gradation,which further leads to the deterioration of pore structure.（4）In IPL ternary system:The activity index of 28 days was up to 95.58%.The proportion of IOTs in the ternary system were the optimal between 33%and 20%.the ratio of LS to PS is optimal in the range of 3:2 and 2:1.In the later stage of hydration,more C-S-H gels were formed with high compactness and few gel pores.The total porosity and gel pores increased,and the pores and the most probable pore size changed little.