Martin Keppert, Dana Koňáková, Vojtěch Pommer, Eva Vejmelková, Robert Černý
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Reactivity of precursors for geopolymerization studied by isothermal calorimetry
The paper deals with analyzes of Isothermal Conduction Calorimetry response obtained during the alkaline activation of four types of precursors (metakaolin, slag and two kinds of waste ceramic powders) to geopolymers. The first two precursors are traditionally used, while the latter two are emerging materials and knowledge of their alkaline activation might have high importance in the recycling of Construction and Demolition Waste. The studied precursors differ each to other not only in the chemical composition, but also in the phase composition—the waste ceramic precursors are highly crystalline. It was found that the total reaction heat evolved in the geopolymerization is directly proportional to the amorphous matter content as well as to the compressive strength of the activated product. This finding can be used as fast evaluation tool in searching of new potential geopolymer precursors. The dissolution and polycondensation steps were observed in all experiments and their kinetics was described by Jander’s equation. While the rate of dissolution step is not dependent on temperature, the polycondensation has been accelerated by the higher temperature. The level of the rate acceleration was described by apparent activation energy; these findings can be useful in tuning of geopolymers curing procedure.
期刊介绍:
Journal of Thermal Analysis and Calorimetry is a fully peer reviewed journal publishing high quality papers covering all aspects of thermal analysis, calorimetry, and experimental thermodynamics. The journal publishes regular and special issues in twelve issues every year. The following types of papers are published: Original Research Papers, Short Communications, Reviews, Modern Instruments, Events and Book reviews.
The subjects covered are: thermogravimetry, derivative thermogravimetry, differential thermal analysis, thermodilatometry, differential scanning calorimetry of all types, non-scanning calorimetry of all types, thermometry, evolved gas analysis, thermomechanical analysis, emanation thermal analysis, thermal conductivity, multiple techniques, and miscellaneous thermal methods (including the combination of the thermal method with various instrumental techniques), theory and instrumentation for thermal analysis and calorimetry.