Use of Magnesium Oxide-cement binders for the production of blocks with lightweight aggregates

Magnesium oxide (MgO)-cement (PC) systems are claimed to provide a sustainable alternative to PC, as MgO is produced by low-temperature f~750°C) calcination of naturally occurring minerals such as magnesite (MgCO₃) or brucite (Mg(OH)₂) precipitated from seawater and brines. In porous or semi porous materials such as blocks and pavers, magnesium oxide forms carbonates thus reabsorbing the carbon dioxide produced during calcining. This study has assessed the effect of reactive MgO and MgO-PC binders on the physical and mechanical properties of blocks made with lightweight aggregates. The blocks have been cured under either 98% relative humidity or wet-dry cycling to assess the effect of curing conditions on binder earbonation. MgO has been found to hydrate extensively to form MgiOHfj, which was partially carbonated to hydromagnesite (4MgC0₃.Mg(QH)₂.4H₂O). After 90 days curing, MgO samples achieved similar compressive strengths to those prepared using PC.