Development And Hydration Mechanism Of Lead Smelting Slag-cement Composite Fil Ling Cementitious Material

In this paper,the lead smelting slag of a Lead-zinc Mine in Hunan province as the main raw material to develop a cementing material for filling using this lead-zinc full tailings of the mine as aggregateso,as to achieve the utilization of lead slag resources,reduce the cost of filling,and protect the ecological environment.Firstly,the mechanical activation method was used to grind lead smelting slag for 80min,100min and 120min to obtain slag powder with different fineness,and analyze the lead smelting slag's particle size and micro-morphology.Then,a composite activator composed of sodium hydroxide and cement clinker was selected to conduct the orthogonal test of lead smelting slag based filling materials.The influence of slag fineness,slag content and activator content on the compressive strength of filling body was studied by range analysis and variance analysis,and the optimal formula of the new composite cementitious material were obtained.From a microscopic perspective,X-ray diffraction?XRD?,Fourier infrared spectrometer?FT-IR?and Scanning electron microscopy?SEM?was used to comprehensively analyze the hydration mechanism of lead smelting slag-cement composite filling cementitious materials.This paper draws the following conclusions through laboratory experiments and theoretical analysis:?1?When the lead smelting slag is ground for 100 minutes to D₅₀0 of 19.93?m,the lead slag content is 40%,the NaOH content is 4%,and the cement clinker content is 56%,the compressive strength of the filling body reaches optimal.When the solid content is74% and the lime-sand ratio is 1:4,the early and late strengths of cemented paste backfill used lead smelting slag-cement composite cementious materials are better than cement cementious materials which can meet this lead-zinc mine's filling strength requirements.?2?The factors influencing the strength of the cemented paste backfill used lead smelting slag-cement composite cementious materials at curing time of 3d and 28d in descending order are:fineness of lead smelting slag,NaOH content,and lead smelting slag content.The factors influencing the strength of the cemented paste backfill used lead smelting slag-cement composite cementious materials at curing time of 7d in descending order are:NaOH content,lead smelting slag fineness,and lead smelting slag content.?3?Compared with cement,the new composite cementitious material hydrates earlier.The hydration reaction generates a large number of needle-shaped ettringite crystals and amorphous C-S-H gels.As the hydration progresses,The main hydration product in the later period was amorphous C-S-H gel.?4?Compared with cement cementing fillers,the hydration products of lead smelting slag-cement composite cementing material fillers at all ages are mainly C-S-H gels,which have better cementation properties with tailings particles.The structure is more dense,so it has higher strength than cement cemented fillers at different curing ages.