Some microstructure properties at early age of ettringite binder based on rich C12A7 calcium aluminate cement

The mineral composition of calcium aluminate cements is traditionally based on CA (monocalcium aluminate-CaO·Al2O3). Recently, a new cement with the main compound of C12A7 (Mayenite) has been developed for rapid hardening binder. This cement is used in conjunction with a sulfate binder to form a new type binder called ettringite binder due to the high quantity of ettringite in the hydration product, opened new possibilities for mortar and concrete formulations. This paper focuses on some microstructure characteristics of the ettringite binder based on a C12A7 rich cement and a hemihydrate at early age. Some important characteristics of this binder were found, such as: short setting time (about 40–50 minutes), rapid expansion just after initial setting time, rapid evolution of porosity and bound water during the first 5 hours of hydration. The correlation between bound water and porosity of hardened binders was also found in this paper. Article history: Received 24 January 2018, Revised 04 April 2018, Accepted 27 April 2018