Recycling MgO from the waste magnesium oxychloride cement (MOC): Properties, CO₂ footprint and reuse in MOC

Recycled magnesia was prepared via using magnesium oxychloride cement (MOC)-based waste as the raw material instead of magnesite through calcination under the temperatures from 600 °C to 1000 °C. The effects of calcination temperature on the components, microstructures, and properties of recycled MgO, and its influence on the performance of MOC containing the recycled MgO were investigated. Results indicated that the reactivity of recycled MgO depended on the calcination conditions, the active MgO content approached 80 wt% through the calcination of MOC-based waste in the temperature range of 700 °C–900 °C. The MOC paste was prepared by using 30 wt% MgO recycled under 800 °C exhibited higher mechanical performance, denser microstructure and more stable volume. The carbon emissions of recycled MgO are 0.49 t/t of magnesia, which is only 31.2% of that emitted by the calcination of magnesite via conventional dry route. This study provides an efficient approach to reducing the consumption of non-renewable natural resources and the generation of construction waste to realize cleaner and sustainable production of reactive MgO.