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akadeemia kirjastus
SINCE 1984
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Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2020): 0.934


Full article in PDF format | doi: 10.3176/oil.2016.4.05



In this paper, the geopolymerization of the solid heat carrier (SHC) ash waste produced at Petroter shale oil plants, Viru Keemia Grupp (VKG), Estonia was studied. Different mixtures were prepared to study and evaluate the potential use of this SHC ash for geopolymer-type mortar and cement production and to compare alkali-activated black ash with the material having self-cemented upon hydration with plain water. Mixtures prepared with plain water and NaOH solution show comparable compressive strength development, but the mixture with NaOH affords significantly lower com­pressive strength values, which can be explained by the absence of an ettringite/monosulphate phase in the NaOH-activated samples. Hydro­calumite precipitated instead of ettringite in the NaOH-activated mixture does not provide the interlocking structure that is found in water mixtures, though the formation of an amorphous geopolymer phase is possibly observed in the NaOH-activated sample after 90 days of curing. Sodium silicate- and Na-silicate/NaOH-activated samples show a strong geopoly­meriza­tion and development of Ca-Na-Al-silicate gel formed in the pore space of the ash aggregate. However, due to strong shrinkage upon drying, the compressive strength obtained after 7 days of curing is lost in the pro­longed curing process, and further research into the causes and prevention of Ca-Na-Al-silicate gel shrinkage is needed.


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