Boosting MgO hydration through sodium bicarbonate: Enhancing the strength of MgO-calcined clay cementitious materials

Abstract

The slow early strength development of MgO-calcined clay cementitious materials poses significant challenges in meeting industrial requirements, thereby limiting their large-scale application. To address this issue, this study employed 1 wt% of sodium bicarbonate to activate the MgO-calcined clay cementitious materials and compared its effectiveness with that of two commonly used early strength agents: calcium chloride and sodium sulfate. The results demonstrated that sodium bicarbonate promoted strength development more effectively than both calcium chloride and sodium sulfate. This enhanced performance was attributed to the superior ability of sodium bicarbonate to facilitate the dissolution of the Mg(OH)2 surface layer formed during the hydration of MgO. Consequently, the reactivity of MgO was improved, leading to the formation of more hydration products. This study provides a pathway for the activation and application of MgO-calcined clay cementitious materials.