CO2-Driven Additive Manufacturing of Sustainable Steel-Slag-Mortars (2024-07)¶

This study presents a sustainable additive manufacturing approach for 3D printing in construction sector, leveraging steel slag as the primary carbonatable binder. Pintable steel slag mortars modified with xanthan gum (XG) as the viscosity modifying agents (VMA) demonstrate superior carbonation reactivity and strength development, thus regarded as the optimal formulation. After 24 h carbonation, the compressive strength of the printed samples generally exceeds 100 MPa and reaches up to 127.1 MPa, the characteristic interlayer bonding strength of the printed samples also reaches 5.5 MPa. Superior mechanical properties can be attributed to the densification and reinforcement mechanisms from the magnesium calcite products. Specifically, the larger magnesium calcite crystals intergrow to densify the matrix, while the tiny crystallites deposit on internal pore walls, repairing these defects. The carbonated printed samples exhibit typical mechanical property anisotropy which, associated with deposition molding process, is further amplified by heterogeneity in the carbonation reaction. Low carbon steel slag feedstock and CO2 capture from carbonation curing achieves net CO2 sequestration for the steel slag 3D printing mortar across the integrated manufacturing cycle, with a quantified carbon footprint of −86.77 kg CO2/m3.