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.