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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


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

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.