Preparation and characterization of magnesium oxalate cement

Abstract

The production of portland cement causes CO₂ emissions. Alternative binders proposed in recent years often rely on scarce materials or use environment-threatening chemicals. Industrial waste CO₂ can be bound into carbonate-based construction materials but the process is slow, and the final product is often a precast block, making concrete lose its advantage of being cast on site. This paper introduces magnesium oxalate cement, a novel acid-base binder made at room temperature from oxalic acid salts and magnesium oxide. The oxalate ion (C₂O₄^2-) has twice the equivalent carbon content of the carbonate ion and oxalic acid (H₂C₂O₄) is one of the simplest multi-carbon chemicals to produce with captured CO₂ using electrochemistry. The direct use of oxalic acid and two different oxalate salts are compared. The strength development and water stability of different magnesium oxalate cements are discussed based on their mineralogies and microstructures. Glushinskite (MgC₂O₄.2H₂O) is the main reaction product in magnesium oxalate mortars, which are shown to reach 28-d compressive strengths up to 45 MPa.