ARTIFICIAL AGGREGATE FROM SINTERED COAL ASH

Fly ash is one of the most commonly used secondary raw materials in the Czech Republic. It is used predominantly for re-cultivation, roads and additions to cement or plasters. The use of fly ash in the technology of sintering-based artificial aggregate was tested in the 1980s. However, the production was stopped for various technological and economic reasons. Nowadays, possibilities for the production of artificial aggregate are tested with fly ash produced in the Czech Republic and could be promising for future technologies, mainly with respect to the stability of production. The paper presents part of the study describing the possibilities of using microsilica and Fe2O3 for the optimization of a raw-material mix and fly-ash body. Three samples of high-temperature lignite combustion fly ash were selected from prospective sources in the Czech Republic. The fly ash was mixed with 5 % or 10 % additions. Then, samples were fired at temperatures of 1150 degrees C and 1200 degrees C. After firing, the physico-mechanical properties of the fly-ash bodies and microstructure were evaluated. The results imply that the addition of microsilica unambiguously improves the quality of the fly-ash body. The addition of Fe2O3 did not take part in the formation of the melt and weakened the fly-ash body's structure.