Synchronous vacuum hot pressing ultra-high performance geopolymer: Ultrafast polymerization and early strength development

To overcome the application bottleneck of geopolymer in high-end industries, this study aims to develop ultra-high performance geopolymer products. By employing Synchronous Vacuum Hot Pressing, we have significantly enhanced the rate of polymerization and mechanical properties of Geopolymer based on Metakaolin-Fly Ash. The influence of Si/Al ratio, alkali equivalent, and molding time on the geopolymerization process, mechanical properties, and microstructure of geopolymers was investigated, while elucidating the underlying mechanisms. The compressive strength of SVHP-MFG reaches 90.92 MPa when the Si/Al ratio is 2, alkali equivalent is 8 %, and molding time is 30 min, owing to increased production of aluminosilicate gels and matrix structure densification. The ongoing reaction of unreacted particles and the subsequent transformation from “alumina-rich gel” to “silica-rich gel” in later stages further enhance the mechanical properties of the material. Additionally, the mean pore diameter of Synchronous vacuum hot pressing of metakaolin-fly ash geopolymer measures below 13.24 nm, thereby significantly enhancing the pore structure of the geopolymer. The synchronous vacuum hot pressing metakaolin fly ash-based geopolymers synthesized in this study represents a novel category of ultra-high performance ceramic-like geopolymers, exhibiting exceptional early strength and early stability. The research aims to promote the application of geopolymer in high-end industry and provide technical and theoretical support for the development of ultra-high performance geopolymer based products.