eesti teaduste
akadeemia kirjastus
SINCE 1984
Oil Shale cover
Oil Shale
ISSN 1736-7492 (Electronic)
ISSN 0208-189X (Print)
Impact Factor (2021): 1.442
PDF | 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.


1.   Provis, J. L., Bernal, S. A. Geopolymers and related alkali-activated materials. Annu Rev Mater Res, 2014, 44, 299–327.

2.   Ots, A. Oil Shale Fuel Combustion. Tallinna Raamatutrükikoda, Tallinn, 2006.

3.   Kearns, J., Tuohy, E. Trends in Estonian oil shale utilization: October 2015. Analysis: International Centre for Defence and Security (Tuohy, E., ed.). Inter­national Centre for Defence and Security, Tallinn, 2015. Available at http://

4.   Liive, S. Oil shale energetics in Estonia. Oil Shale, 2007, 24(1), 1–4.

5.   Mõtlep, R., Kirsimäe, K., Talviste, P., Puura, E., Jürgenson, J. Mineral com­posi­tion of Estonian oil shale semi-coke sediments. Oil Shale, 2007, 24(3), 405–422.

6.   Siirde, A., Eldermann, M., Rohumaa, P., Gusca, J. Analysis of greenhouse gas emissions from Estonian oil shale based energy production processes. Life cycle energy analysis perspective. Oil Shale, 2013, 30(2S), 268–282.

7.   Bauert, H., Kattai, V. Kukersite oil shale. In: Geology and Mineral Resources of Estonia (Raukas, A., Teedumäe, A., eds.). Estonian Academy Publishers, Tal­linn, 1997, 313–327.

8.   Mõtlep, R., Sild, T., Puura, E., Kirsimäe, K. Composition, diagenetic trans­formation and alkalinity potential of oil shale ash sediments. J. Hazard. Mater., 2010, 184(1–3), 567–573.

9.   Reinik, J., Heinmaa, I., Mikkola, J.-P., Kirso, U. Hydrothermal alkaline treat­ment of oil shale ash for synthesis of tobermorites. Fuel, 2007, 86(5–6), 669–676.

10. Reinik, J., Heinmaa, I., Kirso, U., Kallaste, T., Ritamäki, J., Boström, D., Pongrácz, E., Huuhtanen, M., Larsson, W., Keiski, R., Kordás, K., Mikkola, J.-P. Alkaline modified oil shale fly ash: Optimal synthesis conditions and preliminary tests on CO2 adsorption. J. Hazard. Mater., 2011, 196, 180–186.

11. Richardson, I. G. Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate, beta-dicalcium silicate, Portland cement, and blends of Portland cement with blast-fumace slag, metakaolin, or silica fume. Cement Concrete Res., 2004, 34(9), 1733–1777.

12. Golubev, N. Solid oil shale heat carrier technology for oil shale retorting. Oil Shale, 2003, 20(3), 324–332.

13. Talviste, P., Sedman, A., Mõtlep, R., Kirsimäe, K. Self-cementing properties of oil shale solid heat carrier retorting residue. Waste Manage. Res., 2013, 31(6), 641–647.

14. Mindess, S., Young, J. F., Darwin, D. Concrete. Second Edition. Prentice Hall, Pearson Education, Inc., Upper Saddle River, NJ, 2003.

15. Sedman, A., Talviste, P., Kirsimäe, K. The study of hydration and carbonation reactions and corresponding changes in the physical properties of co-deposited oil shale ash and semicoke wastes in a small-scale field experiment. Oil Shale, 2012, 29(3), 279–294.

16. Sedman, A., Talviste, P., Mõtlep, R., Jõeleht, A., Kirsimäe, K. Geotechnical characterization of Estonian oil shale semi-coke deposits with prime emphasis on their shear strength. Eng. Geol., 2012, 131–132, 37–44.

17. Kuusik, R., Uibu, M., Kirsimäe, K., Mõtlep, R., Meriste, T. Open-air deposition of Estonian oil shale ash: formation, state of art, problems and prospects for the abatement of environmental impact. Oil Shale, 2012, 29(4), 376–403.

18. Baur, I., Keller, P., Mavrocordatos, D., Wehrli, B., Johnson, C. A. Dissolution-precipitation behaviour of ettringite, monosulfate, and calcium silicate hydrate. Cement Concrete Res., 2004, 34(2), 341–348.

19. Liira, M., Kirsimäe, K., Kuusik, R., Mõtlep, R. Transformation of calcareous oil-shale circulating fluidized-bed combustion boiler ashes under wet con­ditions. Fuel, 2009, 88(4), 712–718.

20. Clark, B. A., Brown, P. W. Formation of ettringite from monosubstituted calcium sulfoaluminate hydrate and gypsum. J. Am. Ceram. Soc., 1999, 82(10), 2900–2905.

21. Gilbert, I. Creep and shrinkage models for high strength concrete – Proposals for inclusion in AS3600. Aust. J. Struct. Eng., 2002, 4(2), 95–106.

22. Castel, A., Foster, S. J., Ng, T., Sanjayan, J. G., Gilbert, R. I. Creep and drying shrinkage of a blended slag and low calcium fly ash geopolymer Concrete. Mater. Struct., 2016, 68(5), 1619–1628.

23. Bažant, Z. P. Prediction of concrete creep and shrinkage: past, present and future. Nuc. Eng. Des., 2001, 203(1), 27–38.

24. Ridtirud, C., Chindaprasirt, P., Pimraksa, K. Factors affecting the shrinkage of fly ash geopolymers. Int. J. Min. Met. Mater., 2011, 18(1), 100–104.

Back to Issue