Preparation Of Mine Cementitious Filling Materials Using Solid Waste-based Cementitious Material Containing Refining Slag Combined With Superfine Tailings

Based on the common needs of large amount of metallurgical solid waste and ultra-fine tailings,the use of the two materials to prepare mine filling materials is an effective way to solve the environmental problems of solid waste storage and reduce the cost of filling.However,the Ground blast furnace slag(GGBS)converter steel slag(CSS)-desulfurization gypsum(DG)ternary solid waste cementitious materials have the defects of low early strength,too long setting time and poor applicability of ultra-fine tailings,which seriously hinder its popularization and application.In this paper,research was conducted on the collaborative preparation of low-cost green mine filling materials using refining slag(RS),CSS,GGBS,DG,ultra-fine tailings,and other solid mining and metallurgical wastes,with a focus on the early hydration activity of the refining slag and its stimulating effect on the hydration activity of the slag.This paper also discussed the reinforcing effect of the RS-GGBS-CSS-DG cementitious material system on the early strength of the filling material;analyzed the mechanism of hydration,hardening,and strength growth of solid waste-based cementitious materials;analyzed the engineering applications,economic benefits,and carbon emission reduction advantages of the solid waste-based cementitious filling materials.The following are the results or conclusions of the research:1)The results of grinding and activity index showed that the grinding ability of the refined slag was good,and the best unity of early and late activity index could be achieved when grinding alone for 30 min.Mixed milling has a better effect on the mechanical properties of RS-GGBS-CSS-DG solid waste based cementitious material.The cementitious filling material with ultra-fine tailings as aggregate was prepared with a refining slag doping of 18%,which can achieve early strength and quick setting.The amount of AFt generation increases with the increase of refining slag content.Among hydration products,AFt was the main contributor to the 3-day compressive strength,while C-(A)-S-H gel was the main contributor to the 28-day compressive strength.2)C3AH6,C4AH13 and Al(OH)3 gel as hydration products of the refining slag are mainly derived from C12A7 and C3A,the mineral components in the refining slag.Due to their relatively high hydration reaction speed,they quickly consume a large amount of free water in the slurry,resulting in an earlier loss of plasticity of the slurry,which can effectively stimulate the gypsum ternary solid waste-based slag-converter slag-desulfurization cementitious material,improve the early hydration reaction rate,and shorten the setting time of the filling slurry.The accelerated effect of refining slag on hydration reaction of cementitious materials effectively improves the early compressive strength of backfill and makes up for the performance defects of cementitious materials of solid waste of converter slag.Through a dynamic analysis using the Krstulovic-Dabic model,it is found that the hydration reaction of solid waste-based cementitious materials mixed with 15%to 20%refining slag did not undergo the phase boundary reaction control process,indicating that refining slag was beneficial to increase the concentration of watersoluble products,which maked the barrier of ion migration increase sharply,the reaction speed of phase get fast,and the hydration products continue to form and spread rapidly.3)The solid waste based cementitious material,produced through the process of wind selective grinding pretreatment and ball mill mixed grinding,can achieve the best effect.Using refining slag-based cementitious filling materials for filling and mining can not only meet the relevant production standards of various indicators,but also save 53.76%of the filling material cost per year.Using 1 ton of solid waste-based cementitious materials can reduce CO2 emissions by up to 863 kg,and replacing cement with solid waste-based cementitious materials for filling is a feasible solution in terms of carbon neutrality,with a notable net emission reduction effect.The low-cost cementitious filling materials prepared using solid metallurgical wastes such as refining slag as well as ultra-fine tailings have good work performance and mechanical properties,as well as good economic and carbon emission reduction advantages,which is one of the most effective ways to realize recycling and comprehensive utilization of various solid mining and metallurgical wastes.