Geopolymerization of waste products can contribute to the solution of current environmental issues related to depletion of natural resources. In this paper, several geopolymer mixes are prepared using waste brick in powdered form, while different alkaline activators and curing conditions are applied. Experimental results show that the reaction rate at early age decreases with the increasing silicate modulus as well as with the rise of curing temperature; the reaction is though significantly slower than, e.g., for metakaolin-based geopolymers because of the low content of amorphous phase in the brick. The most compact microstructure is observed for geopolymers with highest reaction rate at early age; with increasing silicate modulus of the activator and decreasing curing temperature the compactness gradually decreases and the specific pore volume increases. Thermal analysis shows a decreasing weight loss with increasing silicate modulus for all temperatures, while dehydration of N-A-S-H and C-A-S-H gels are identified as the most important factors. Dehydroxylation of muscovite is found for the mixtures cured at temperatures up to 60°C only, and decomposition of calcium carbonate just for 20°C curing. Most crystalline phases detected by X-ray diffraction analysis in designed geopolymers are identical to those found in the raw precursor, which indicates only a partial geopolymerization and presence of a significant amount of unreacted particles. For geopolymers cured at 60°C and 80°C, formation of zeolitic phases is observed. While sodalite and chabazite are found only in mixtures with higher reaction rate, gismondine appears in geopolymers with higher silicate modulus.
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