Energy-saving calcination of hydromagnesite for sustainable magnesia-based cement: A new route towards MgO production

The MgO production worldwide is mainly achieved through the calcination of magnesite in the wake of higher energy requirements. This study proposes an energy-saving calcination strategy through low-temperature partially calcining hydromagnesite (4MgCO 3 ·Mg(OH) 2 ·4H 2 O). Furthermore, the feasibility of using the partially calcined hydromagnesite and slag to produce a sustainable cementitious material was investigated by various techniques. This approach requires relatively low temperature and short processing time with a potential energy saving of production and CO 2 emission of fuel combustion. Moreover, it accelerates the hydration rate due to amorphous magnesium carbonate. Results indicated that the amorphous magnesium carbonate is formed during the partial calcination of hydromagnesite. It tends to transform to nesquehonite (MgCO 3 ·3H 2 O) in the initial stage of hydration, which is responsible for promoting early hydration and excellent early compressive strength. Finally, the reaction mechanism of the partially calcined hydromagnesite-based cementitious materials has been established, demonstrating its enormous potential for preparing low-carbon cementitious materials.