Recent trends in mechanochemical processing of fly ash aluminosilicate materials (geopolymers): advancement, challenges, and opportunities

For achieving sustainable development in terms of waste to wealth, low CO2 production, and recycling, geopolymers can be recognized as a practicable alternative. The current review presented a brief study of the potential usage of class F fly ash as a raw material for geopolymer, the chemistry of geopolymerization, and recent development in the field. A brief status of fly ash-based geopolymers (cement, concrete, coating material) is also presented and the research findings are critically analyzed. The new era of one-part geopolymer and mechanochemical grinding-based advanced geopolymers is also discussed to indicate the advancement of fly ash geopolymers globally. Up to a certain extent microstructure, particle size/fineness and effective leaching of amorphous Si/Al from fly ash in the alkaline solution can enhance the mechanical and physical properties of geopolymer material; on the other hand, chemical properties are controlled by milling or mechanochemical grinding. This review also recapitulates the remarkable findings and conclusions of reviewed literature. Understanding 111 indexed research articles from different data sources may provide a productive and precise document for future research. In the last section, challenges and opportunities for fly ash geopolymers are discussed with a special preference for their chemical composition and synthesis mechanism.