Effect of Sodium Hydroxide on Preparation and High Temperature Mechanical Properties of Geopolymers
The aim of this study is to explore new ways of resource utilization of lithium pyroxene tailings and refining slag.The effects of sodium hydroxide addition,water glass addition and the doping ratio of lithium pyroxene tailings and refining slag on the mechanical properties of geopolymers were analyzed through one-way and orthogonal experiments.On this basis,we focused on the influence of the change of sodium hydroxide addition on the preparation of lithium pyroxene tailings-refin-ing slag based geopolymer and its mechanical properties,and analyzed the influence of sodium hydroxide on the microstruc-ture of geopolymer by using the characterization means such as XRD,SEM,FT-IR and so on.The results showed that the 28 d compressive strength of the geopolymer was up to 26.78 MPa when the ratio of lithium pyroxene tailings to refinery slag was 7:3,the addition of water glass was 15 mL,and the addition of sodium hydroxide was 2 g.The addition of sodium hydroxide had the most significant effect on the preparation of geopolymer among the three influencing factors.When the alkalinity of lithium pyroxene tailings was too high,the dissolution of silica-oxygen tetrahedra and aluminium-oxygen tetra-hedra was slowed down or inhibited,thus affecting the synthesis of C—S—H gels and N—A—S—H gels.XRD and SEM anal-yses showed that,with the increase of the content of sodium hydroxide,the generated gels firstly increased and then decreased,and at the same time,they combined with the substances such as bluestone,which increased the degree of densification of the geopolymer.In addition,the loss of compressive strength of the lithium pyroxene tailings-refinery slag-based geopolymer was small at 800 ℃,indicating its good high temperature resistance.
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