Geopolymer

About: Geopolymer is a research topic. Over the lifetime, 6776 publications have been published within this topic receiving 157991 citations. The topic is also known as: geopolymers.

Chemical and Structural Microanalysis of Aluminosilicate Geopolymers Synthesized by Sodium Silicate Activation of Metakaolinite

Abstract: An earlier study by the authors on the chemical optimization of compressive strength in aluminosilicate inorganic polymers (geopolymers), produced by sodium silicate activation of metakaolinite (MK), has been extended to provide chemical analysis of the principal microstructural features using scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) measurements. SEM imaging reveals the presence of a two-phase microstructure; the matrix phase being the fully formed inorganic polymer, while the grain phase is reminiscent of, but chemically dissimilar to, the MK precursor. The current study has provided the following insights into microchemical optimization of compressive strength: (1) The overall chemical composition of the starting materials does not accurately predict the chemical composition of the geopolymer matrix due to incomplete dissolution of the starting material. (2) The ideal Na:Al molar ratio of 1.0 required for charge balance in the bonding network has been observed for the matrix. (3) As the nominal Si:Al molar ratio for the final material increases, the grain Si:Al ratio increases steadily from the MK value, without resulting in the full dissolution of the grain. These results underline the importance of using SEM/EDS microchemical analysis for designing chemical processing conditions for strength-optimum geopolymers, rather than relying on imaging or bulk chemistry in isolation, which may provide misleading results.

The engineering properties and microstructure of sodium carbonate activated fly ash/ slag blended mortars with silica fume

Abstract: Highly concentrated and corrosive alkaline activators are often used for activating polycondensation reactions of aluminosilicate minerals in geopolymers at elevated temperatures. This study investigated the interaction between Pulverised Fuel Ash (PFA), Ground Granulated Blast Furnace Slag (GGBS) and Silica Fume (SF) activated with small dosages of low alkalinity sodium carbonate and sodium silicate. Tests were inclusive of assessments on the consistency and setting behaviours, mechanical strengths and microstructure properties. Results were compared with Ordinary Portland Cement (OPC) mortars and sodium hydroxide activated geopolymer mortars which were established through an existing study. The mechanical strength of sodium carbonate activated geopolymer was found to be comparable with that of the sodium hydroxide activated geopolymer. Geopolymer mortars with 4% of silica fume exhibited the highest mechanical strength. The sodium carbonate activated binder system comprised largely of an interconnected calcium carbonate crystals framework and C-A-S H gels.