The effect of the rate of alumina release during the reaction of a one-part (just-add-water) geopolymer mix on growing geopolymer gels is investigated by coupling time-resolved and spatially resolved infrared spectroscopic analysis. The rate of alumina release from different precursors has previously been identified as a critical controlling factor in the formation of mechanically strong and durable geopolymers; however, its influence on the nanostructure of the geopolymer gel has never before been directly analyzed. Gel microstructure and nanostructure are able to be observed by synchrotron radiation-based infrared microscopy (SR-FTIR) with hierarchical clustering analysis, conducted in conjunction with the in situ attenuated total reflectance (ATR) FTIR technique to provide temporal resolution. The SR-FTIR technique provides the opportunity to analyze the chemistry of the heterogeneous geopolymer binder at a level of detail that previously has not been available. Although spatially averaged (ATR-FTIR) infrared results show similar spectra for well-cured samples with different alumina release rates, SR-FTIR shows that the gels are markedly different, with less unreacted silica particles remaining in geopolymer gels with slow alumina release, but greater homogeneity when alumina is released more rapidly. Rapid release of alumina is shown to impede the dissolution of silica particles in the early stages of the reaction; thus, the participation of alumina in forming geopolymer gels appears to be more beneficial to geopolymer nanostructural development when it becomes available in the later stages of the reaction process.

In geopolymer technology, silicate solutions are frequently used as alkali activators to dissolve the solid aluminosilicate precursor and aid in binder formation. These corrosive and often viscous solutions are not user-friendly and would be difficult to use for bulk production. Developing geopolymers as a one-part mixture ("just add water"), similar to Portland cement, increases their commercial viability. Here, for the first time, the geopolymer system consisting of geothermal silica and solid sodium aluminate (providing the solid silica, alkali, and alumina sources) is studied. The effects of water content, high early silica, and high early alumina in the formation of one-part mix geopolymers are also investigated. This system demonstrates that making geopolymers from solid sources by "just adding water" is possible. XRD shows that the formulation with less water has an unexpected greater extent of crystallinity. It is also observed that a high early Al concentration inhibits geopolymerization, while a high early Si concentration enhances the reaction.

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