The Preparation And Modification Of Geopolymers Based With Different Solid Wastes

Geopolymers is a class of inorganic aluminosilicate polymer mainly composed of electrovalent bond and covalent bond. It has some unique properties which include low shrinkage, high early strength, freeze-thaw resistance, corrosion resistance, sulphate resistance, low energy consumption and long durability. It is widely applied in engineer, due to various of raw material, easy process and low CO₂ let out. The main works and results of the dissertation are as followed:1 Using fly ash, slag and metakaolin as basic ingredient, KOH as alkali activator, synthesized a series of fly ash-based geopolymers. Through the result of compressive strength, the best ratio of metakaoline fly ash and tail coal is 3:3:5 with 15% of KOH. The highest strength could reach to 36.36MPa. When the amount of alkali activator is over capacity, the matrix's compressive strength will decrease. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the structure of geopolymer is amorphous.2 The fly ash, desulfurization ash and kaolin have been employed to prepare the geopolymer. Compressive strength test demonstrate that the Optimization conditions are 30% of desulfurization ash, 20% of kaolin and the ratio of alkali and raw material is 0.5. The sequence of the factors studied by orthogonal test is the addition of desulfurization ash > ratio of alkali and raw material > the addition of kaolin. The XRD and SEM result show that there is not new crystalline phase produced. The main crystalline phase of the matrix is non-reacted mullite in fly ash. Fourier transform infrared spectrum reveals that infrared peak caused by [AlO4] shifts to lower wave number. Mass spectroscopy (TG/MS) are used to analyze the components of ion current for those compositions volatilizing easily from desulfurization ash and geopolymer. It is suggested that CO₂ and SO₂ didn't emit from geopolymer.3 Due to the defects of geopolymer in mechanical properties, such as poor flexural strength, glass fiber and polyvinyl alcohol fiber are used to increase the flexural strength. The results show that the glass fiber have reinforcing and toughening effect on geopolymer and that polyvinyl alcohol fibers greatly increase its flexural strength, but the compressive strength has declined.