Due to the large amount of CO2 emitted from the production process of traditional portland cement-based building materials, thenew low-carbon cementing materials represented by geopolymer have become a research hotspot in recent years. Fly ash, as a bulk industrial solid waste in China, is rich in aluminosilicates, and the preparation of geopolymer by alkali - activated method can realize thebulk consumption of fly ash. In this paper, the evaluation method of alkali-activated reactivity of fly ash was discussed, the reaction mechanism of fly ash and alkali activator was summarized, the effects of key factors such as fly ash type, activator, raw material ratio and curing system on the properties of geopolymers were summarized, and the existing problems in current research were proposed, and the future research directions from the perspective of evaluation of active components of fly ash and elemental composition of alkali activationsystem were prospected. The reactivity evaluation methods of fly ash mainly include Rietveld full spectrum fitting method, saturated limesolution absorption method and acid-base dissolution method. The reaction process of alkali-activated fly ash can be divided into four stages: dissolution, gelation, condensation and polymerization. The dissolved Si/ Al molar ration from fly ash in the process of decompositionhas an important influence on the gel structure and mechanical properties of geopolymer, and the optimal Si/ Al molar ration obtained bydifferent studies has a great difference. The effects of raw material ratio, curing system, gel structure and other factors on the propertiesof geopolymer obtained by different studies has a great difference, which brings difficulties to the research on the mechanism of fly ash alkali excitation reaction and the synthesis of geopolymer. In the future, a unified calculation method for the proportion of elements in alkaliactivated fly ash should be established according to the physical and chemical properties of different types of fly ash, laying a theoreticalfoundation for the unified design standard of fly ash-based geopolymer synthesis.

孙浩(1997—),男,河北张家口人,硕士研究生。E-mail:2513787907@qq.com

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SUN Hao,MA Zhibin,LU Guangjun,et al.Review on geopolymer preparation by alkali activation of coal fly ash[J].CleanCoal Technology,2023,29(11):140-153.