Critical review of the properties of MgO - magnesium carbonate cements

MgO can be sourced from magnesium silicates or desalination brines with no direct CO 2 emissions from the raw materials. This paper critically reviews available literature on magnesium carbonate cements prepared from MgO, water and magnesium carbonates such as nesquehonite or hydromagnesite. Such MgO - magnesium carbonate cements develop high early strength due to the formation of hydrous carbonate-containing brucite (HCB), which incorporates both carbonate and H 2 O into its structure. Hydrated magnesium carbonate cements have a high potential to bind additional CO 2 . In the presence of SiO 2 , magnesium silicate hydrates (M-S-H) also form, which exhibit a high resistance to carbonation. The Mg/Si ratio governs the phase assemblage, as silica can react with HCB to form M-S-H. Magnesium carbonate and silicate hydrate cements have a pH value ranging from 10 to 11, demonstrate a high resistance to leaching, while the corrosion rate of steel rebars is comparable to PC.