Ceramics-Silikáty 54, (4) 362 - 367 (2010)

Geopolymer material based on coal fly ash from the high temperature combustion activated with alkali silicate is a very cheap and suitable material for temporary and non-load-bearing structures. For the purposes of emergency application, such as closing barriers, it is necessary to have dry mixtures ready for mixing with water. However, the utilization of dried sodium silicate activator instead of an aqueous solution considerably delays its setting. The application of C₁₂A₇ accelerates the setting of alkali activated fly ash, but it also influences its mechanical properties. Early-age strengths are increased, the long term strengths are, however, deteriorated in comparison with the pure material without C₁₂A₇. Microstructural changes are described by means of mercury intrusion porosimetry, SEM, XRD and FTIR analysis.