Alkali Activated Magnesium-rich Nickel Slag-fly Ash Geopolymer Preparation And Properties

With the accelerated pace of urbanization and industrialization in China,more and more industrial solid wastes are generated,and nickel slag is one of the many solid wastes.The amount of nickel slag piled up in China is increasing year by year,but due to its low activity cannot be reasonably used,these large amounts of piled up nickel slag not only occupy the land,but also seriously pollute the environment.Improving the activity of nickel slag and preparing it as a geopolymer cementing material with excellent performance can effectively solve this problem.In this thesis,the low-activity industrial solid waste magnesium-nickel slag is used as the main raw material,and the fly ash is used as the batch material.The geopolymer cementitious material is prepared by the orthogonal experiment method and geopolymerization technology,and the optimal mixing ratio is determined.The microstructure of the samples was analyzed by XRD,FTIR,SEM and other characterization methods.In view of the low activity of magnesium-nickel-rich slag,remelting water quenching and phase-separation treatment was carried out to improve its pozzolanic activity.The mechanical properties of activated magnesium-rich nickel slag-fly ash geopolymers were also studied,and the effect of replacing some alkali activators with waste glass on the mechanical properties of geopolymers was preliminarily explored.The main research work and conclusions of the paper are as follows:Firstly,using magnesium-nickel-rich slag and fly ash as the main raw materials,and sodium silicate-Na₂CO₃as the alkali activator,the mass ratio of magnesium-nickel-rich slag and fly ash,the content of composite alkali activator（sodium silicate-Na₂CO₃）and the Influence of water-cement ratio on mechanical properties of geopolymer cementitious materials.The results shows:when the mass ratio of magnesium-rich nickel slag to fly ash is 3:7,the content of sodium silicate is 15%,the modulus is 1.2,the content of Na₂CO₃is 4%,and the water-cement ratio is 0.30,the prepared glue The pure slurry of coagulating material has the best mechanical properties,the compressive strength of curing 28d can reach 37.5 MPa,and the weather resistance is good.The main products leading to the improvement of the strength of the gelling material are calcium silicate hydrate,（N-A-S-H）and（N-M-A-S）amorphous gel phases.Secondly,the effect of phase separation on the structure and gelation activity of magnesium-rich nickel slag was studied by remelting water quenching method,and characterized by alkali dissolution,XRD,FTIR,TEM and other methods.The results shows:The dissolved amount of Si,Al and Ca elements in the magnesium-rich nickel slag after phase separation increased significantly,and the compressive strength of the geopolymer was increased by 78.9%compared with the previous one,which indicated that the method of remelting and water quenching was effective for the magnesium-rich nickel slag.have a positive impact.The increased activity of the magnesium-rich nickel slag after phase separation is related to the changes in mineral phase and microstructure caused by remelting and water quenching,and more amorphous glass phases and Si and Ca-rich phases appear after phase separation,This facilitates the dissolution of Si,Al and Ca elements.Finally,the mechanical properties of activated magnesium-rich nickel slag-fly ash geopolymers were studied,and the effect of replacing some alkali activators with waste glass on the mechanical properties of geopolymers was preliminarily explored to solve the high cost of alkali activators and waste glass pollution.environmental issues.The result shows:The geopolymer prepared by activating magnesium-rich nickel slag combined with fly ash has a compact structure,and the strength is greatly improved compared with that of the unactivated nickel slag,and the highest compressive strength can reach 73.01 MPa,and good weather resistance.As the percentage of waste glass substituted for alkali activator increases,the strength of the geopolymer decreases significantly.