Insights into phase assemblage in MgO-Al2O3-(SiO2)-CO2 systems

Abstract

Abstract

The decarbonization of the cement industry will require a versatile portfolio of different alternative cements. In contrast to other known and popular alternatives, cement based on MgO-rich hydrates remains an unexplored topic and little is known about the formation and stability of Mg-Al LDH as the main binding phase in a cement. In this work, we report on experimental work on the phase assemblage of MgO-Al2O3-(SiO2)-CO2-H2O system via the hydration of an amorphous magnesium aluminate (AMA) in the presence of different magnesium carbonates and metakaolin. The data reveal that hydrotalcite is the main hydrate of the cement with relatively fast reaction kinetics in which AMA is fully hydrated after 7 days of curing in ambient water. Additionally, a more detailed phase assemblage will be beneficial in the better understanding and in improving the thermodynamic data for the MgO-Al2O3-(SiO2)-CO2-H2O system and of interest to shed light on the long-term stability of this cement.