Improvement of 3D Printing Properties of MgO Derived Binders by CO2 Curing in Hardened State (2025-05)¶

The cement industry uses energy resources intensively, resulting in significant carbon emissions. Magnesium-based binders, including the use of reactive MgO cement (RMC), are considered a promising alternative to cement. Three-dimensional (3D) printing technology has the advantages of unlimited flexibility, reduced cycle time, low labor cost and minimal waste. In this study, the improvement of 3D printing properties (rheological and mechanical) of MgO-derived binders by CO2 curing in hardened state was investigated. Rheological measurements (yield stress and viscosity) and compressive tests have been performed. The yield stress and viscosity of the reference sample were 173 Pa and 3.9 Pa.s, respectively, and 12.5%, 18.75%, 25% and 31.25% rMgO substitution increased the yield stress by 156%, 157%, 174%, and 224%, and viscosity by 105%, 156%, 269%, and 610%, respectively, compared to the reference sample. The reason for these increases is the improvement of hydration kinetics with the increase in the amount of rMgO with higher purity. As the rMgO ratio increases, the compressive strength also increases. CO2 curing has increased compressive strength compared to the curing with room conditions. The increase in rMgO, which acts as a hydration agent, and the carbonation of RMC have led to the formation of HMC by forming continuous networks, filling pores, densifying the matrix microstructure, and thus facilitating strength development. The rMgO substitution ratio with optimum properties in terms of 3D printability is 31.25% and the compressive strength, yield stress and viscosity are 11.8 MPa, 561 Pa and 27.7 Pa.s, respectively.