Research On Composition And Performance Of Geopolymer Based On Metakaolin And Slag

Because of the various of materials,it can hardly to establish a normalized standard to research and evaluate the performance(especially for its mechanical property)of geopolymer,which is the key problem that hinder the development of geopolymer.In this paper,geopolymer is made by adjustment the oxide contents of the raw material(slag,meta-kaolin and silica fume),and the formation zone in CaO-Al2O3-SiO2 ternary system is confirmed,and the influence of oxide content in different formation zone on compressive strength is studied.The results show that the formation zone of geopolymer is,the SiO2 content is between 40%?80%,the Al2O3 content is between 3%?25%,the CaO content is between 0%?48%.The formation zone can divided to 3 mainly part by CaO content.Low CaO content zone(CaO content is between 0%?10%).of which the compressive strength is between 3MPa?20MPa.Medial CaO content zone(CaO content is between 10%?40%),of which the compressive strength is between 20 MPa?60MPa.High CaO content zone(CaO content is between 40%?48%),of which the compressive strength is between 60MPa?80MPa.The research shows that refer to inorganic mineral polymer,the strength of high calcium system>the strength of medium calcium system>the strength of low calcium system.And in different systems,inorganic mineral polymer is different with the change of n(SiO2)/n(Al2O3)ratio.Moreover,establish a mathematical model according to 28d compressive strength(Y)of geopolymer paste,n(SiO2)/n(Al2O3)molar ratio(X1)in raw material composition,n(CaO)/n(SiO2+Al2O3)molar ratio(X2)and water glass rmodulus(X3).Y = 16.81 + 4.14×l460×X2/(X1+X3)Microscopic analysis illustrate that geopolymer of calcium system makes the advantages of high calcium system and low calcium system yield well,also keep the lamellar structure in low calcium system.Low calcium is constituted main by N-A-S-H gel,high calcium is constituted main by C-A-S-H gel,medium calcium is constituted main by N-A-S-H gel and C-A-S-H gel.The incorporation of CaO renders pores in lamellar structure get effectively filled,as well as improves mechanical properties of geopolymer.With n(CaO)/n(SiO2+Al2O3)increases,namely CaO content in cementitious materials accounted for proportion is more and more,the 3d,7d and 28d strength are on the whole show increasing trend no mater how the rate of Si/Al change.