Research And Development Of Phosphogypsum-based Mine Cementing Material

This paper developed the phosphogypsum-based filling materials and the phosphogypsum-full tailings filling materials that binder is ultra-sulphur phosphogypsum slag cement and aggregate is pyrite tailings or copper tailings, which based on the previous study of ultra-sulphur phosphogypsum slag cement and readjust the ratio.The new filling materials have great economic and social benefits and are suitable for mine filling.The paper researched strength, setting time etc physical properties and liquidity etc basical performance of the filling materials by physical and chemical method, And analyzed the microscopic mechanism of filling materials by laser granularity, XRD and SEM etc methods.The paper also compared the performance of the phosphogypsum-full tailings filling materials with P.C32.5cement-full tailings filling material.The results showed that:The phosphogypsum-based filling materials with steel slag as the alkaline exciting agent, in which phosphogypsum slurry content can reach67%.The best mix proportion of the filling material is:phosphogypsum slurry of67%, slag of20%, steel slag of13%, and polycarboxylate superplasticizer of0.2%, the mass concentration of66%-69%. It with portland cement clinker as the alkaline exciting agent, in which phosphogypsum slurry content can reach86%. The best mix proportion of the filling material is:phosphogypsum slurry of86%, clinker slag powder of10%, slag of4%and polycarboxylate superplasticizer of0.2%.The fluidity of the filling materials is great.The compressive strength of the filling material sample at7days exceed2.0MPa, meets the requirement of mine filling strength, the compressive strength at28days has a large surplus for mine filling.The best mix proportion of the binder of the phosphogypsum--pyrite tailings filling material is:phosphogypsum slurry of23%, slag of48%, clinker of4%, steel slag of25%.When the ash sand ratio is1:4and the mass concentration is62%, the compressive strength of the filling material at7days can reach2.25MPa, satisfies the requirement of mine filling strength.The best mix proportion of the binder of the phosphogypsum-copper tailings filling material is:phosphogypsum slurry of28%, slag of48%, clinker of4%, steel slag of20%. When the mass concentration is72%, the ash sand ratio is1:4, the strength of the filling material at3days can reach2.5MPa.The experimental results show that:compared to the P.C32.5cement-full tailings filling material, the performance of the filling material is superior and it have a wider range of ash sand ratio.It analyzed microscopic cementing mechanism of phosphogypsum-full tailings filling material and the influence of steel slag dosage on structure the filling material system by microscopic testing method. The results show that hydration products of the binder of the filling material is ettringite crystal and C-S-H gel.The tailings did not participate in the hydration reaction, and it only acts as filling aggregate. Hydration products C-S-H gel and ettringite gets the tailings bond together, fills gaps in the system at the same time, to achieve the effect of cementation. Cementing effect of the filling material is closely related to the cotent of ettringite produced by hydration reaction of cementing agent, so a proper dosage of steel slag in cementing agent is the key factor to affect the strength of the filling material.