Effect of Calcium Nitrate on the Performance of Slag Blended Cement

Abstract:

Portland cement has been replaced with 50% ground, granulated blastfurnace slag (ggbs) of two types. The influence of 2 and 4% calcium nitrate accelerator on early hydration of such binders was investigated by isothermal calorimetry as well as X-ray diffraction and thermogravimetry. The strength development of mortar based on these binder blends has been followed up to 28 days and the influence of calcium nitrate discussed. One ggbs lower in SiO₂, A_l2O₃ and MgO yielded somewhat lower strength (about 90%) than the other. Addition of calcium nitrate led to lower strength at 1 day, but higher strength from 3 days on-wards. The blends with the two ggbs achieved similar strength at 7 and 28 days when blended with 4% calcium nitrate. Calcium nitrate led to more ettringite formation and AF_m phases (probably nitrate version) at 1-day sealed curing. However, the calcium hydroxide content was reduced. Potential explanations for calcium hydroxide reduction are discussed.

• Periodical: Advances in Science and Technology (Volume 145)
• Pages: 45-54
• DOI: https://doi.org/10.4028/p-feNFc4
• Online since: March 2024
• Authors: Harald Justnes*, Tobias Danner, Mehrdad Torabzadegan
• Keywords: Accelerator, Blastfurnace Slag, Calcium Nitrate, Calorimetry, Cement, Strength

References

[1] H. Justnes, How to Make Concrete More Sustainable, Journal of Advanced Concrete Technology, Vol. 13, March 2015, pp.147-154.

DOI: 10.3151/jact.13.147

[2] H. Justnes, H. and E.C. Nygaard, The Setting Accelerator Calcium Nitrate - Fundamentals, Performance and Applications, Proceedings of 3rd CANMET/ACI International Symposium on Advances in Concrete Technology, August 24-27, 1997, Auckland, New Zealand, ACI SP-171, pp.325-338.

DOI: 10.14359/6104

[3] J. Skibsted and R. Snellings, Reactivity of supplementary cementitious materials (SCMs) in cement blends, Cement and Concrete Research, Vol. 124, 2019, 105799.

DOI: 10.1016/j.cemconres.2019.105799

[4] Justnes, H.: "Alternative Setting Retarders for Portland Cement Clinker", Proceedings of the 20th International Conference on Superplasticizers and Other Chemical Admixtures in Concrete, ACI SP-329, Beijing, China, 28-31 October 2018, paper SP-329-17, pp.201-211 (ISBN-13: 978-1-64195-029-9).

DOI: 10.14359/51711215

[5] H. Justnes and E.C. Nygaard, Calcium Nitrate - A Multifunctional Admixture for High Performance Concrete, Proceedings of the International RILEM Conference "The Role of Admixtures in High Performance Concrete", Ed. J.G. Cabrera and R. Rivera-Villarreal, Monterrey, México, March 21-26, 1999, pp.199-212.

[6] M. Balonis, M. Medala and F.P. Glasser, Influence of calcium nitrate and nitrite on the constitution of AFm and Aft cement hydrates, Advances in Cement Research, Vol. 23, 2011, pp.129-143.

DOI: 10.1680/adcr.10.00002

[7] T.Dorn, T. Hirsch and D. Stephan, Working mechanism of calcium nitrate as an accelerator for Portland cement hydration, Journal of American Ceramic Society, Vol. 126, 2023,pp.725-766.

DOI: 10.1111/jace.18782

[8] H. Justnes, A Review of Chloride Binding in Cementitious Systems, Nordic Concrete Research, Publication no. 21, 1/98, 1998, pp.48-63.

[9] H. Basset and H. Taylor, The three component system: Calcium nitrate – lime-water, Journal of Chemical Society, Vol. 105, 1914, pp.1926-1941.

[10] T.I. Rozenberg, G.D. Kucheryaeva, G.D. Medvedeva, Investigation of new compounds formed in systems CaO-Ca(NO3)2-H2O and CaO-Ca(NO2)2-H2O and of their role in the process of hardening of cold concretes with admixtures on the base of calcium nitrate and nitrite (in Russian), in the book Eksperiment v oblasti tekhnicheskogo mineraloobrazovaniya, Moscow, Nauka, 1975, pp.119-122.