Abstract
Alkali sulphates are chemical products that can be used to activate and improve the performance of mineral additions, like Blast-Furnace Slag (BFS) and Fly Ash (FA). This study investigates the effect of two alkali sulphates (sodium sulphate and potassium sulphate) on delayed deformations of mortars containing a high content of BFS. Autogenous shrinkage is monitored after 2 days and basic creep tests are conducted on 28-day-old specimens loaded at 30% of their compressive strength. Their microstructure is characterized by using several experimentations, such as internal relative humidity measurements, thermogravimetry analysis and a water porosity test. A numerical model in terms of C-(A)-S-H content evolution is applied to quantify the degree of hydration advancement. The results show that the use of sodium sulphate leads to a higher autogenous shrinkage, but to a lower specific creep. This is linked to the fact that the mortars activated with sodium sulphate show a faster hydration rate and a lower porosity, which results in higher capillary pressures. However, this also limits the movement of water required for creep development.
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Acknowledgements
: The authors would like to show gratitude to Rennes Métropole which financed a part of the equipment used in the present study.
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Li, L., Hannawi, K., Darquennes, A. (2023). Delayed Deformations of Na- and K- Sulphates Activated Blast-Furnace Slag Mortars. In: Jędrzejewska, A., Kanavaris, F., Azenha, M., Benboudjema, F., Schlicke, D. (eds) International RILEM Conference on Synergising Expertise towards Sustainability and Robustness of Cement-based Materials and Concrete Structures. SynerCrete 2023. RILEM Bookseries, vol 44. Springer, Cham. https://doi.org/10.1007/978-3-031-33187-9_38
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