Performance And Mechanism Analysis Of Quartz-type Iron Tailings Powder And Waste Rock In Cement-based Materials

With the continuous development of economy,the tailings produced by mining has become the most solid waste in China.The environmental and safety problems of tailings storage are increasingly prominent.The amount of concrete used in construction is huge,and there are many gaps in high-quality concrete aggregate and mineral admixture.Because of low cost,iron tailing full tailings filling has become the main direction of mine filling,but the problems of high bleeding rate and low early strength seriously restrict its development.Therefore,it is of great significance to study the influence and mechanism of iron tailing powder and waste rock on the performance of cement-based materials to solve the problem of iron tailing solid waste storage,relieve the pressure of concrete raw materials,and ensure the safety and environmental protection of mine filling.In this paper,by using iron tailings as aggregate to prepare concrete,iron tailings powder as mineral admixture to prepare concrete,iron tailings full tailings to prepare filling slurry.Combined with macro test,micro test and theoretical analysis,the influence of iron tailings powder and waste rock on the performance of cement-based materials and the mechanism of iron tailings powder in cement-based materials are studied.Research contents and achievements are as follows.(1)Through the macro mechanical test and micro test analysis of iron tailings concrete and iron tailings fine grinding powder in alkaline environment,the strengthening effect of iron tailings aggregate on the mechanical strength of concrete was studied..Combined with the micro test and analysis,it is revealed that the broken Si-O bond and Al-O bond will regroup to form compound salt minerals with calcium silicate and calcium aluminosilicate as the main substances in alkaline environment,the conditions of broken bond recombination are clarified,and the model of broken bond recombination is established.(2)Through experimental study of the mechanical properties of concrete with different amount of iron tailing powder,the influence of iron tailing powder on the long-term compressive strength of concrete is analyzed.The reasonable amount of iron tailing powder is within 50%of the total amount of mineral admixture.The strength-age prediction model of iron tailings powder concrete was established,and the mechanism of iron tailings powder in concrete was revealed based on the theory of broken bond recombination.(3)Through the carbonation test of iron tailings powder concrete,it is found that the accelerated carbonation depth in 28d,the natural carbonation depth in 1d and 28d after curing all increase with the increase of the content of iron tailings powder.The ratio of iron tailings to mineral admixture and the 28d compressive strength are introduced to establish the prediction model of iron tailings concrete carbonation.(4)Through the fast freeze-thaw test of iron tailings powder concrete,it is found that adding a certain amount of iron tailings powder properly can improve the frost resistance of concrete.Based on the hole structure analysis of NMR,it is found that iron tailing powder can effectively improve the proportion of harmless holes and less harmful holes in concrete,so as to improve the frost resistance of concrete.(5)Based on the experimental study of sulphate corrosion of iron tailings powder concrete,it is found that proper amount of iron tailings powder can improve the sulphate corrosion resistance of concrete.Combined with the micro analysis,the mechanism of sulphate degradation of iron tailings powder concrete and the mechanism of sulphate corrosion resistance of iron tailings powder are revealed.(6)Based on the strength development law of sulfate full immersion and half immersion in long-term concrete,the prediction curve equation of corrosion time and relative compressive strength factor of iron tailings powder concrete in sulfate solution is established.The curve equation has strong correlation and can effectively predict the long-term mechanical properties of iron tailings powder concrete in sulfate environment.(7)Through the experimental study on the bleeding rate,sink shrinkage rate and strength of the filling material of iron tailing full tailings,it is shown that the high water solidifying agent can effectively reduce the bleeding rate of the slurry,and improve the early strength of the filling body at the same time.Combined with the analysis of SEM,EDS and IR,the regulation mechanism of the high water solidifying agent on the bleeding characteristics of the filling slurry of iron tailing full tailings is revealed.