Title:
Impact of OPC-Based Activation on Microstructure of Super Sulphated Slag Cement
Author(s):
Emmanuel Guillon and Catherine Bouillon
Publication:
Symposium Paper
Volume:
349
Issue:
Appears on pages(s):
522-532
Keywords:
activation, calorimetry, hydration, low carbon concrete, microstructure development, super sulphated slag cement
DOI:
10.14359/51732769
Date:
4/22/2021
Abstract:
The industrialization of Super Sulphated Slag Cement requires a strict control of the activation of slag. Optimal activator content is a compromise between early age and long term strengths. In particular, an excessive activator dosage leads to a strong decrease of final strength that could lead to non-conformities. Thanks to the coupled use of mechanical testing, SEM and isothermal calorimetry, this paper provides a clearer insight on how SSSC reacts. It is shown that excess of activation impacts mechanical strength twofold. First, it is observed after one or two days of hydration a decrease of hydration kinetics that could be attributed to a denser or thicker hydrate layer around slag particles. Second, overactivated SSSC exhibit heterogeneous porosity including defects that leads to a decrease of strength and lower mechanical efficiency. Finally, this paper highlights that the increase of strength observed when using hemihydrate is mainly due to the improvement of hydration kinetics, more than a gypsum setting effect.
Related References:
1. Shi C., Krivenko P. V., Roy D. (2006) Alkali-Activated Cements and Concretes, Taylor & Francis, ISBN10: 0–415–70004–3
2. Ouellet-Plamondon C., Habert G.(2015), Life Cycle Assessment (LCA) of alkali-activated cements and concretes, in Handbook of Alkali-Activated Cements, Mortars and Concretes, pp663-686, ed. F. Pacheco-Torgal & al, ISBN 978-1-78242-276-1.
3. Gruskovnjak A., Lothenbach B., Winnefeld F., Figi R., Ko S.C., Adler M., Mäder U. (2008) Hydration Mechanisms of Super Sulphated Slag Cement, in Cement and Concrete Research 38, pp. 983-992
4. Bellmann F., Stark J. (2009) Activation of Blast Furnace Slag by a New Method, in Cement and Concrete Resarch 39, pp644-650.
5. Bijen J., Nïel E. (1981) Supersulphated Cement from Blastfurnace Slag and Chemical Gypsum Available in the Netherlands and in Neighbouring Countries, in Cement and Concrete Research 11, pp. 307-322.
6. Denes N., Piesting M. (1998) Hydraulishes Bindermittel, patent AT408 983 B.
7. Maekawa K. Ishida T. Kishi (2009) Multi-Scale Modeling of Structural Concrete, Taylor & Francis, ISBN10: 0-415-46554-0
8. Han F. He, X. Zhang Z. Liu J. (2017) Hydration Heat of Slag or Fly-Ash in the composite Binder at different temperatures, in Thermochimica Acta 655, pp202-210.
9. Guillon E., Termkhajornkit P., Chen J. (2011), Analysis of chemical shrinkage experiments on blended cement paste via a coupled thermodynamic/kinetic hydration model, in Proceedings of Cementing a sustainable future : XIII ICCC International Congress on the Chemistry of Cement ; Madrid, 3-8 July, 2011
10. F. Tomosawa (1974), A Hydration model of cement, Proceedings of Annual Meeting on Cement Technology, Cement Association of Japan, Vol.28, 53-57
11. Malhotra V.P, Sai A.S.R, Kapur P.C. (1982), Plaster of Paris Activated Supersulfated Slag Cement, in Cement and Concrete Research 12, pp. 463-473.
12. Nishino T. (1996) Hydration of calcium sulfate hemihydrate in dilute aqueous suspension, J-Stage Inorganic Materials vol. 3 issue 260 pp10-16, doi: 10.11451/mukimate1994.3.10