Abstract
Two kaolin ores with the almost same fineness and purity of original kaolinite but possessing different kaolinite crystallinity (Hinckley Index) were selected to study the influence of crystallinity and calcination conditions on the pozzolanic activity of metakaolin after dehydroxylation. The different calcination conditions were conducted by altering the calcination temperature and holding time to obtain different metakaolin samples with different degrees of dehydroxylation. Then pozzolanic activities of metakaolin samples were tested by the modified Chapelle test, Frattini test and strength evaluations. Additionally, the apparent activation energies of two kaolin ores were calculated to study the thermal properties of kaolinite by isoconversional methods followed by iterative computations. The results showed that pozzolanic activities were dependent on the degree of dehydroxylation, except for the metakaolins calcined at 900℃ due to the fact that recrystallization and high pozzolanic activity was conducted by complete dehydroxylation (degree of dehydroxylation ≥ 90%). Moreover, the lower crystallinity of original kaolinite favored the removal of the structural hydroxyls, leading to a reduction of apparent activation energy and increase of pozzolanic activity, indicating that the higher calcination temperature or longer holding time was required during calcination to reach the same degree of dehydroxylation and finally highly ordered kaolinite converted into the less active metakaolinite, which was confirmed by the lower Ca(OH)2 consumption in the modified Chapelle test, higher [CaO] and [OH] in the Frattini test and weaker compressive strength.
Go to article
Bibliography
1. Akahira, T. and Sunose, T. 1969. Trans. Joint Convention of Four Electrical Institutes. Paper No. 246. Research Report, Chiba Institute of Technology (Science Technology) 16, pp. 22.
2. ASTM C618:2013. Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete.
3. Badogiannis et al. 2005 – Badogiannis, E, Kakali, G. and Tsivilis, S. 2005. Metakaolin as supplementary cementitious material: Optimization of kaolin to metakaolin conversion. Journal of Thermal Analysis and Calorimetry 81(2), pp. 49–79.
4. Bich et al. 2009 – Bich, C., Ambroise, J. and Péra, J. 2009. Influence of degree of dehydroxylation on the pozzolanic activity of metakaolin. Applied Clay Science 44(3), pp. 194–200.
5. Cao et al. 2016 – Cao, Z., Cao, Y., Dong, H., Zhang, J. and Sun, C. 2016. Effect of calcination condition on the microstructure and pozzolanic activity of calcined coal gangue. International Journal of Mineral Processing 146, pp. 23–28.
6. Cyr et al. 2006 – Cyr, M., Lawrence, P. and Ringot, E. 2006. Efficiency of mineral admixtures in mortars: quantification of the physical and chemical effects of fine admixtures in relation with compressive strength. Cement and Concrete Research 36, pp. 264–277.
7. Donatello et al. 2010 – Donatello, S., Freeman-Pask, A., Tyrer, M. and Cheeseman, C.R. 2010. Effect of milling and acid washing on the pozzolanic activity of incinerator sewage sludge ash. Cement and Concrete Composites 32, pp. 54–61.
8. EN 196-1:2005. Methods of Testing Cement. Part 1: Determination of strength.
9. EN 196-5:2005. Methods of Testing Cement. Part 5: Pozzolanicity Test for Pozzolanic Cement.
10. Ferraz et al. 2015 – Ferraz, E., Andrejkovičová, S., Hajjaji, W., Velosa, A.L., Silva, A.S. and Rocha, F. 2015. Pozzolanic activity of metakaolins by the french standard of the modified chapelle test: a direct methodology. Acta Geodynamica et Geomaterialia 179, pp. 289–298.
11. Frías et al. 2000 – Frías, M., Sánchez de Rojas, M.I. and Cabrera, J. 2000. The effect that the pozzolanic reaction of metakaolin has on the heat evolution in metakaolin-cement mortars. Cement and Concrete Research 30, pp. 209–216.
12. Galos, K. 2011. Composition and ceramic properties of ball clays for porcelain stoneware tiles manufacture in Poland. Appled Clay Science 51(1), pp. 74–85.
13. Gao et al. 2001 – Gao, Z., Nakada, M. and Amasaki, I. 2001. A consideration of errors and accuracy in the isoconversional methods. Thermochimica Acta 369, pp. 137–142.
14. Janotka et al. 2010 – Janotka, I., Puertas, F., Palacios, M., Kuliffayová, M. and Varga, C. 2010. Metakaolin sand- -blended-cement pastes: rheology, hydration process and mechanical properties. Construction and Building Materials 791, pp. 802–24.
15. Kakali et al. 2001 – Kakali, G., Perraki, T., Tsivilis, S. and Badogiannis, E. 2001. Thermal treatment of kaolin: the effect of mineralogy on the pozzolanic activity. Applied Clay Science 20, pp. 73–80.
16. Kissinger, HE. 1957. Reaction Kinetics in Differential Thermal Analysis. Analytical Chemistry 29(11), pp. 1702–1706.
17. Liu et al. 2000 – Liu, Q, Xu, H. and Zhang, P. 2000. Crystallinity difference for various origin of kaolinites in coal measures. Journal of China Coal Society 25(6), pp. 576–580 (in Chinese).
18. Murat, M. 1983. Hydration reaction and hardening of calcined clays and related minerals I. Preliminary investigation on metakaolinite. Cement and Concrete Research 13, pp. 259–266.
19. NF P18-513:2010. Metakaolin. Pozzolanic addition for concrete. Definitions, specifications and conformity criteria.
20. Ozawa, T. 1965. A New Method of Analyzing Thermogravimetric Data. Bulletin of the Chemical Society of Japan 38(11), pp. 1881–1886.
21. Qiu et al. 2014 – Qiu, X., Lei, X., Alshameri, A., Wang, H. and Yan, C. 2014. Comparison of the physicochemical properties and mineralogy of Chinese (Beihai) and Brazilian kaolin. Ceramics International 40, pp. 5397–5405.
22. Sabir et al. 2001 – Sabir, B.B., Wild, S. and Bai, J. 2001. Metakaolin and calcined clays as pozzolans for concrete: a review. Cement and Concrete Composites 23, pp. 441–454.
23. Saikia et al. 2002 – Saikia, N., Sengupta, P., Gogoi, P.K. and Borthakur, P.C. 2002. Kinetics of dehydroxylation of kaolin in presence of oil field effluent treatment plant sludge. Applied Clay Science 22, pp. 93–102.
24. Samet et al. 2007 – Samet, B., Mnif, T. and Chaabouni, M. 2007. Use of a kaolinitic clay as a pozzolanic material for cements: Formulation of blended cement. Cement and Concrete Composites 29(10), pp. 741–749.
25. Sinthaworn, S. and Nimityongskul, P. 2011. Effects of temperature and alkaline solution on electrical conductivity measurements of pozzolanic activity. Cement and Concrete Composites 33, pp. 622–627.
26. Tironi et al. 2012 – Tironi, A., Trezza, M.A., Irassar, E.F. and Scian, A.N. 2012. Thermal treatment of kaolin: effect on the pozzolanic activity. Procedia Materials Science 1, pp. 343–350.
27. Tironi et al. 2013 – Tironi, A., Trezza, M.A., Scian, A.N. and Irassar, E.F. 2013. Assessment of pozzolanic activity of different calcined clays. Cement and Concrete Composites 37, pp. 319–327.
28. Tironi et al. 2014 – Tironi, A., Trezza, M.A., Scian, A.N. and Irassar, E.F. 2014. Thermal analysis to assess pozzolanic activity of calcined kaolinitic clays. Journal of Thermal Analysis and Calorimetry 117, pp. 547–556.
29. Wild et al. 1996 – Wild, S., Khatib, J.M. and Jones, A. 1996. Relative strength, pozzolanic activity and cement hydration in superplasticised metakaolin concrete. Cement and Concrete Research 26, pp. 1537–1544.
30. Zhang et al. 2015 – Zhang, Y., Xu, L., Seetharaman, S., Liu, L., Wang, X. and Zhang, Z. 2015. Effects of chemistry and mineral on structural evolution and chemical reactivity of coal gangue during calcination: towards efficient utilization. Materials and Structures 48, pp. 2779–2793.
Go to article
en
pl
