MgO/hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O, abbreviated as HY) blends are cementitious materials, which set and harden when mixed with water. These blends reach acceptable strengths and therefore can potentially be used as binders in mortars and concrete. In case MgO is derived from carbonation of magnesium silicates and subsequent calcination, MgO/HY blends offer the possibility to be used as alternative binders with reduced carbon footprint compared to normal portland cement-based products.
This study focuses on the characterization of hydration products and mechanical properties of MgO/HY blends. Hy-dration of solely MgO leads to formation of brucite (Mg(OH)₂) without any strength-building properties. In contrast, by blending MgO with hydromagnesite, it is possible to produce mortar samples with a strength of up to 11.0 ± 0.4 MPa (1595 ± 58 psi) after 28 d. Moreover, blending with hydromagnesite accelerates early hydration of MgO. XRD and TGA studies of hydrated blends revealed the presence of brucite and of a poorly crystalline, unidentified hydrate phase. The latter might play an important role in strength development.