Effect of steel slag on rheological and mechanical properties of sulfoaluminate cement-based sustainable 3D printing concrete

The low utilisation of steel slag has led to a worsening of environmental problems. This study aims to use tri-potassium citrate (TPC) to activate the cementitious properties of steel slag and further apply sulfoaluminate cement (SAC) as supplement to design low-carbon composites. 3D printing technology can help to reduce materials consumption as well as labour cost; therefore, the advent of SS-SAC-3D printing concrete has the potential to enhance the utilisation of low-carbon composites and reduce process emissions. This study investigates the effects of steel slag and its activation on the properties of 3D-printed concrete. Workability, rheology, setting time and buildability tests were conducted. The strength differences and anisotropy between the printed and molded specimens were compared. The results demonstrate that adding aluminium-rich steel slag altered the ratios between aluminate and sulfate phases, shortened the setting time, and improved the fluidity and rheological properties of the mixture. The addition of 25 %–50 % steel slag can effectively promote the occurrence of composite hydration reactions, improve the strength to reach over 42.5 MPa (standard strength of SAC) at late ages, and significantly reduce carbon emissions. In conclusion, the SS-SAC-3DPC has the potential to become a significant building material owing to its cost-effectiveness and printability, which can meet the requirements of general building structures. More importantly, its application could contribute to a reduction in the carbon footprint of the construction industry. • Effect of steel slag on 3D printed concrete based on sulfoaluminate cement is revealed. • Mechanism of steel slag on fresh and mechanical properties of 3DPC is discussed. • Buildability of steel slag-sulfoaluminate cement-based 3DPC is tested. • Carbon emission and environmental benefit of the 3DPC are evaluated. • Optimal amount of steel slag in the 3DPC is proposed for reference.