Unlocking unexplained characteristics of MgO: a review by RILEM TC 311-MBC

Abstract MgO-based cements hold promises as alternatives to Portland cement with radically reduced carbon footprint. MgO plays a centric role in the reaction and formation of these cements. This review is a part of RILEM TC-311 MBC where we discussed the current understanding about the behaviors of MgO in magnesium carbonate (MC) and magnesium silicate (MS) cements. In addition, we reviewed practices in characterizing MgO and available processes to produce MgO in industrial scale. There are several unexpected and unexplained phenomena which likely link to the characteristics of MgO in both MC and MS cements. This distinguishes the MgO-cements from Portland cement and eventually several practices and know-how commonly used in cement research are not applicable and need further insights. Furthermore, the selection of MgO type and characteristics seems crucial to achieve the desired properties for both MC and MS cements. We also point out research needed in this topic to pave the way for MgO-based cements to progress toward their promises.