Abstract
AbstractGeopolymers have the potential to function as an environmentally friendly substitute for ordinary Portland cement, with up to 80% less CO2 emission during production. The effect is best utilized for geopolymers prepared with amorphous silica instead of waterglass (Na2xSiyO2y+x) to adjust the Si:Al ratio. The reactivity of the precursors with the alkaline activator affects the final mineralogical properties of the binder. The purpose of the present study was to investigate the amount of different phases formed during geopolymerization and to understand the quantitative evolution of carbonation during geopolymer synthesis by determining the solubility of metakaolinite and amorphous SiO2 in NaOH at various concentrations. The solubility was studied by ICP-OES measurements. X-ray diffraction was used for qualitative and quantitative phase analysis of the geopolymers. The solubility of the precursors increased with calcination temperature of metakaolinite, reaction time for amorphous SiO2, and at higher NaOH concentrations. Partial dissolution resulted in free Na+, which is a source for the formation of carbonates in the geopolymers. Thermonatrite occurred prior to trona formation in all samples.
Funder
Deutsche Forschungsgemeinschaft
Publisher
Springer Science and Business Media LLC
Subject
Earth and Planetary Sciences (miscellaneous),Geochemistry and Petrology,Soil Science,Water Science and Technology
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