Study On Preparation And Hydration Mechanism Of Alkali Activated Copper And Nickel Slag Cementitious Materials

Copper and nickel slag is a kind of industrial by-product produced by smelting copper and nickel.A large amount of copper and nickel slag is piled up in Xinjiang,which not only occupies farmland but also causes serious environmental pollution.Therefore,how to absorb solid waste in bulk and reduce the accumulation of copper and nickel slag is a problem that needs to be considered at present.It is a feasible solution to this problem to prepare copper and nickel slag as cementitious material for mine filling materials.Therefore,this paper first studied the copper and nickel slag glass and crystal phase of space structure,and quantitative calculation of its content,alkali dissolution characteristics of the glass phase were studied and calculated the gelation of copper and nickel slag activity index,then by physical activation and chemical activation method was prepared by alkali excitation copper nickel slag cementitious materials,and its hydration hardening mechanism are discussed.The main contents are as follows:(1)Copper and nickel slag is composed of crystal phase Fayalite,Mg-Rich((Fe,Mg)₂SiO₄)and a small amount of glass phase.The content of glass phase and crystal phase was quantitatively calculated by XRD-Rietveid and low concentration HF dissolution method.The results showed that the content of Fayalited,Mg-Rich was 72.42%,while the content of glass phase was only 27.58%.FT-IR spectra and Raman spectra of Copper and nickel slag show that the spatial structure of crystalline phase is isolated island[SiO₄]^4-structure,and that of glass phase is reticulated[SiO₄]^4-structure.(2)Compared with salt solution,alkaline solution(such as NaOH solution,Na₂SiO₃solution)can promote the fracture of chemical bond of glass phase,so that the depolymerization reaction of[SiO₄]^4-tetrahedron and[Al O₄]^5-tetrahedron in glass phase and the dissolution of more Si,Al and Ca ions.And the larger the specific surface area of copper and nickel slag,the higher the concentration of Na₂SiO₃ solution,the more intense the glass phase dissolution reaction.The copper and nickel slag(grinding 50 min,the median diameter D50 8.30?m)gelling activity index is 0.70,which shows that it has certain potential activity of gelation.(3)Both physical activation and chemical activation can promote the participation of copper and nickel slag in hydration reaction.The longer the grinding time,the better the cementitious activity of copper and nickel slag.Compared with Na₂SO₄ and NaOH,Na₂SiO₃has the best effect on copper and nickel slag,the compressive strength of the composite cementitive material is the highest.In addition,the addition of mineral admixture slag powder(GGBFS)can improve the compressive strength of copper and nickel slag composite cementitious materials.When the content of GGBFS is 43%and the activator is 7%solid Na₂SiO₃,the 3-day and 28-day compressive strength of copper and nickel slag composite cementification materials can reach 79MPa and 125MPa respectively.(4)The hydration of cooper and nickel slag is a process of depolymerization and recondensation of glass phase.Under the action of the activator,the chemical bond of the network-modifying breaks and the active Ca²⁺is released.Network intermediates and forming of Si-O-Al and Si-O-Si chemical bonds between fracture makes the high degree of polymerization of[SiO₄]^4-tetrahedron and depolymerization of[Al O₄]^5-tetrahedron generated after low polymerization degree of Si(OH)and Al(OH).And the low degree of polymerization of Si(OH)and Al(OH)react with Ca²⁺complete the polycondensation reaction generated C-(A)-S-H gel,which provide strength.The research in this paper shows that cooper and nickel slag has potential cementification activity,and can be prepared into cementitious materials for mine filling materials by physical and chemical activation methods.