| Abstract [eng] |
In this work, the influence of hydrothermal treatment conditions and aluminum oxide additive on the formation of calcium aluminum silicate hydrates as well as their adsorption properties and the effect of these compounds on the early Portland cement hydration were examined. The hydrothermal synthesis of calcium silicate hydrates was performed for 4, 8, 16, 48 and 72 hours at 130 °C, when the molar C/S and A/(A+S) ratios of the primary mixtures were equal to 0.55 and 0.05, 0.10, 0.15, respectively. It was determined that not only the amount of additive, but also the duration of hydrothermal treatment influenced the formation of calcium aluminum silicate hydrates. The optimal conditions of these compounds hydrothermal synthesis are: the temperature of isothermal curing – 130 °C, duration – 8 h, and the molar A/(A+S) ratio of primary mixture – 0,15 (C/S = 0.55). It was examined, that the chemical nature of adsorptive had a significant influence on the intercalation rate of heavy metal ions: the highest adsorption capacity was reached for iron ions (49.99 mg Fe3+/g). It was determined and proved by the kinetical calculations, that substitution reactions characteristic to the mentioned compounds are irreversible, i. e. almost all Fe3+, Cu2+, Mn2+, Zn2+, Co2+ and Ni2+ ions was adsorbed by chemical interaction. Moreover, the selectivity sequence for heavy metals ions of calcium aluminum silicate hydrates can be written as follows: Fe3+> Cu2+> Mn2+> Zn2+> Co2+> Ni2+. It was found, that calcium aluminum silicate hydrates intercalated with heavy metal ions accelerate the early hydration of Portland cement, although the total amount of the heat evolution rate of Portland cement is higher (236 J/g) than in the samples with mentioned additives (230 J/g). |
