Skip to main content
SpringerLink
Log in

Effect of fly ash on the microstructure of cement mortar

  • Published:
Materials and Structures Aims and scope Submit manuscript

Abstract

A microstructural study of mortars prepared with a low-alkali, low-C3A cement and a Class F fly ash, both of Swedish origin, was carried out using the scanning electron microscopy-energy-dispersive X-ray analytical technique. Supplementary phase analyses were made by X-ray diffraction and thermogravimetry-differential thermal analysis. Normally, CH crystals in the transition zone grow with their c axis parallel (or the (0 0 1) cleavage plane perpendicular) to the aggregate surface. The encapsulation of the fly ash particles by the growing CH reduces the amount of orientated CH at the aggregate-paste interface. The growth mechanism of these crystals is discussed. The reduction of CH, most significant after 28 days of hydration, is mainly due to the reaction of CH with the fly ash glass phase. Initially, the replacement of cement by fly ash weakens the paste-aggregate interfacial zone due to reduction of contact points, and increases the local water-to-cement ratio. This, however, improves significantly when the fly ash has reacted. In order to enhance the reaction of fly ash, extra gypsum was added. The results show that gypsum can accelerate the fly ash reaction, but the products formed, and the beneficial effects of gypsum, are mainly determined by the total amount of gypsum in the paste.

Resume

Une étude microstructurale de mortiers préparés à partir de ciment à faible teneur en alcali et en C3A ainsi que de cendres volantes de classe F (tous deux d’origine suédoise) a été menée en se servant du microscope électronique à balayage et de la technique d’analyse de rayons X à dispersion d’énergie. Les phases supplémentaires étaient étudiées par thermogravimétrie et analyse thermique différentielle.

Normalement, les critaux de CH croissent dans la zone de transition en sorte que leur axe est parallèle à la surface du granulat (ou le plan de clivage (0 0 1) perpendiculaire à la surface). En croissant le CH recouvre les cendres volantes, ce qui réduit la quantité de CH orienté à l’interface pâte-granulat. La diminution de CH, très importante après 28 jours, semble dépendre surtout de la réaction entre les cristaux de CH et la phase vitreuse des cendres volantes.

Au début de l’hydratation, l’addition de cendres volantes affaiblit la zone d’interface entre la pâte et le granulat en réduisant les points de contact. Le rapport eau-ciment local est aussi augmenté. Une fois que la réaction des cendres volantes commence, la situation s’améliore de façon significative. Afin d’augmenter la réactivité des cendres volantes, on a ajouté du gypse. Les résultats démontrent que, bien que le gypse puisse accélérer la réaction des cendres volantes, la formation de produits de réaction, ainsi que les avantages, dépendent de la quantité totale de gypse dans la pâte.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Berry E. E. and Malhotra, V. M., ‘Fly Ash in Concrete’, CANMET, Ottawa; SP85-3 (1986).

    Google Scholar 

  2. Takemoto, K. and Uchikawa, H., ‘Hydration of pozzolanic cement’, in Proceedings of 7th International Congress on the Chemistry of Cement, Paris, 1980, Vol. I (Editions Septima, Paris) pp. IV-2–I-29.

    Google Scholar 

  3. Montgomery, D. G., Hughes, D. C. and Williams, R. I. T., y ‘Fly ash in concrete—a microstructure study’,Cem. Concr. Res. 11 (1981) 591–603.

    Article  Google Scholar 

  4. Kokubu, M., ‘Fly ash and fly ash cement’, in Proceedings of 5th International Congress on Chemistry of Cement, Tokyo, 1968, Vol. IV (Cement Association of Japan, Tokyo) pp. 75–113.

    Google Scholar 

  5. Gutteridge, W. A. and Dalziel, J. A., ‘Filler cement: the effect of secondary component on the hydration of Portland cement, Part 2. Fine hydraulic binders’,Cem. Concr. Res. 20 (1990) 853–861.

    Article  Google Scholar 

  6. Idem.,, ‘Filler cement: The effect of secondary component on the hydration of Portland cement, Part 1. A fine non-hydraulic filler’,ibid. 20 (1990) 778–782.

    Article  Google Scholar 

  7. Diamond, S., ‘The characterization of fly ashes’, in ‘Effects of Fly Ash Incorporation in Cement and Concrete’, Materials Research Society Symposium N, Boston, 1981, pp. 12–23.

  8. Cabrera, L. G. and Plowman, C., ‘The influence of pulverized fuel ash on the early and long term strength of concrete’, in Proceedings of 7th International Congress on the Chemistry of Cement, Paris, 1980, Vol. III (Editions Septima, Paris) pp. IV 84–92.

    Google Scholar 

  9. Huang, S., ‘Hydration of Fly Ash Cement and Microstructure of Fly Ash Cement Pastes’, CBI Research 2.81 (Swedish Cement and Concrete Research Institute, Stockholm, 1981).

    Google Scholar 

  10. Diamond, S., ‘Mimimal pozzolanic reaction in one year old fly ash pastes: an SEM evaluation’, in Proceedings of 11th International Conference on Cement Microscopy, New Orleans, 1989 (International Cement Microscopy Association, Duncanville, TX) pp. 263–274.

    Google Scholar 

  11. Xu, A. and Sarkar, S. L., ‘Gypsum activated fly ash hydration in cement pastes’,Cem. Concr. Res.,21 (1991) 1137–1147.

    Article  Google Scholar 

  12. Wendlandt, W. W., ‘Thermal Analysis’, 3rd Edn (Wiley, London, 1986).

    Google Scholar 

  13. Pope, M. I. and Judd, M. D., ‘Differential Thermal Analysis’ (Heyden, London, 1977).

    Google Scholar 

  14. Ramachandran, V. S., ‘Estimation of Ca(OH)2 and Mg(OH)2—implications in cement chemistry’,Israel J. Chem. 22 (1982) 240–246.

    Google Scholar 

  15. Schwiete, H. E. and Ludwig, U., ‘Crystal structures and properties of cement hydration products (hydrated calcium aluminates and ferrites)’, in Proceedings of 5th International Symposium on the Chemistry of Cement, Tokyo, 1968, Vol. II (Cement Association of Japan, Tokyo) pp. 37–67.

    Google Scholar 

  16. Grandet, J. and Ollivier, J. P., ‘Nouvelle méthode d’étude des interfaces ciment-granulats’, Proceedings of 7th International Congress on the Chemistry of Cement, Paris, 1980, Vol. III (Editions Septima, Paris) pp. VII 85–89 (in French).

  17. Larbi, J. A. and Bijen, J. M., ‘Evolution of lime and microstructural development in fly ash-Portland cement specimens’,Mater. Res. Soc. Symp. Proc. 178 (1990) 127–138.

    Google Scholar 

  18. Idem.,, ‘Orientation of calcium hydroxide at the Portland cement paste-aggregate interface in mortars in the presence of silica fume: a contribution’,Cem. Concr. Res. 20 (1990) 461–470.

    Article  Google Scholar 

  19. Grandet, J. and Ollivier, J. P., ‘Orientation des hydrates au contact des granulats’, in Proceedings of 7th International Congress on the Chemistry of Cement, Paris, 1980, Vol. III (Editions Septima, Paris) pp. VII 63–68 (in French).

  20. Barnes, B. D., Diamond, S. and Dolch, W. L., ‘The contact zone between Portland cement paste and glass “aggregate” surfaces’,Cem. Concr. Res. 8 (1978) 233–243.

    Article  Google Scholar 

  21. Massazza, F. and Costa, U., ‘Bond: paste-aggregate, paste-reinforcement and paste-fibres’, in Proceedings of 8th international Congress on the Chemistry of Cement, Rio de Janeiro, 1986, Vol. I (Finep Publications, Rio de Janeiro) pp. 158–180.

    Google Scholar 

  22. Buckley, H. E., ‘Crystal Growth’ (Wiley, London, 1951).

    Google Scholar 

  23. Taylor, H. F. W., ‘Chemistry of cement hydration’, in Proceedings of 8th International Congress on the Chemistry of Cement, Rio de Janeiro, 1986, Vol. I (Finep Publications, Rio de Janeiro) pp. 82–110.

    Google Scholar 

  24. Copeland, L. E. and Kantro, D. L., ‘Hydration of Portland cement’, in Proceedings of 5th International Symposium on the Chemistry of Cement, Tokyo, 1968, Vol. II (Cement Association of Japan, Tokyo) pp. 386–421.

    Google Scholar 

  25. Kondo, R. and Ueda, S., ‘Kinetics and mechanisms of the hydration of cements’,ibid. in pp. 203–255.

    Google Scholar 

  26. Larbi, J. A. and Bijen, J. M., ‘Effects of water-cement ratio, quantity and fineness of sand on the evolution of lime in set Portland cement systems’,Cem. Concr. Res. 20 (1990) 783–794.

    Article  Google Scholar 

  27. Berntsson, L., Chandra, S., and Kutti, T., ‘Principles and factors influencing high-strength concrete production’,Concr. Internatl 12(12) (1990) 59–62.

    Google Scholar 

  28. Ahmed, S. J., Glasser, L. S. D. and Taylor, H. F. W., ‘Crystal structures and reactions of C4AH12 and derived basic salts’, in Proceedings of 5th International Symposium on the Chemistry of Cement, Tokyo, 1968, Vol. II (Cement Association of Japan, Tokyo) pp. 118–127.

    Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Division of Building Materials, Chalmers University of Technology, Göteborg, Sweden

    A. Xu & L. O. Nilsson

  2. Faculty of Applied Sciences, University of Sherbrooke, J1K 2R1, Sherbrooke, Québec, Canada

    S. L. Sarkar

Authors
  1. A. Xu
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. S. L. Sarkar
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. L. O. Nilsson
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Xu, A., Sarkar, S.L. & Nilsson, L.O. Effect of fly ash on the microstructure of cement mortar. Materials and Structures 26, 414–424 (1993). https://doi.org/10.1007/BF02472942

Download citation

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF02472942

Keywords

Search

Navigation