碱激发剂中钠、硅对CFB飞灰合成地聚物的影响

以偏高岭土掺加石灰石和石膏模拟循环流化床(CFB)飞灰,研究了不同SiO2/Al2O3和Na2O/Al2O3对烧粘土材料合成地聚物过程中,凝结时间和抗压强度的变化规律;借助X射线衍射和拉曼图谱分析,证明了CFB合成地聚物过程中存在10种主要化学反应.同时发现:碱激发剂中钠含量变化主要影响活性硅、铝单体数量的多少,活性硅含量增加更有利于生成CSH和(Na,Ca)-PSS型地聚物;在SiO2-Al2O3-CaO-Na2O体系中,当Na2O/Al2O3≥1.1时,反应体系因生成水化石榴石而改变地聚反应历程,进而对样品抗压强度产生负效应;SiO2/Al2O3≥3.0时,样品凝结迅速,不利搅拌.

Effects of Silicon and Sodium Content in Alkali Activator on the Formation of Geopolymer Prepared by Circulating Fluidized Bed Fly Ash

The mixture of metakaolin and calcite or gypsum instead of circulating fluidized bed (CFB) fly ash was used to investigate the influence of SiO2/Al2O3 and Na2O/Al2O3 on the setting time and compressive strength of geopolymer.The results of X-ray diffraction (XRD) and Raman spectrum proved that there are 10 chemical reactions occurred in the preparation of metakaolin-based geopolymer.The experimental results also showed that: the variation of sodium components in alkali activator controlled the amount of complex silicon or aluminum anion group, and the formation of CSH and (Na, Ca)-PSS depended on the amount of complex silicon anion group.In the SiO2-Al2O3-CaO-Na2O system, the formation of hydrogarnet showed negative effect on the strength development of geopolymer when Na2O/Al2O3≥1.1, and the geopolymer product set too fast to mix properly when SiO2/Al2O3≥3.0.