Magnesium-based cements for CO₂ capture and utilisation

Magnesium from reject desalination brine is reacted at atmospheric pressure and 25-65 °C with CO₂ from industrial effluent combustion gas, precipitating preferably nesquehonite, MgCO₃.3H₂O. Nesquehonite can be thermally activated so that, when remixed with water, it is self-cementing. At ambient temperature, cure durations are typically ∼ 1-3 days. The nesquehonite-based product contains ∼ 32 wt% sequestered carbon dioxide and, at end of use, can be recycled without loss of CO₂. As an application example, cast nesquehonite products are suitable to form lightweight, incombustible building materials with densities in the range 700-900 kg/m³. Compressive strengths of the cast products are low, ca 2-4 MPa, thus application is envisaged to be broadly similar to that of gypsum-based products.