Development of Sustainable Strain-Hardening Cementitious Composites Containing Diatomite for 3D Printing (2025-02)¶

3D concrete printing (3DCP) faces challenges in the automated integration of reinforcement. The use of strain-hardening cementitious composites (SHCCs) with high ductility offers a promising solution to this issue. However, the high cement content in printable SHCC increases the carbon footprint, contributing to heavy environmental burden. This study investigates using diatomite (DE), a natural sedimentary rock, to develop sustainable SHCC for 3DCP. Diatomite partially replaces ordinary Portland cement, and the effects of various DE replacement ratios (10%, 20%, 30%) on fresh properties, mechanical properties, hydration, and microstructure are experimentally examined. Sustainability analysis is conducted using life cycle assessment (LCA). Results show that a 30% DE replacement ratio increases the dynamic yield stress, static yield stress, and plastic viscosity by 31.7%, 79.7%, and 239.5%, respectively. A 10% DE replacement achieves the highest mechanical properties, with tensile, compressive, and flexural strengths increased by 54.6%, 14.0%, and 27.4%, respectively, compared to the reference group. A 10% DE replacement ratio enhances the hydration process with increased calcium silicate hydrate (C-S-H) gels formation and refines the microstructure. DE replacement ratio above 20% negatively impacts hydration due to insufficient portlandite, while the porous structure of unhydrated DE increases the total porosity by 18.4%. LCA results show a 25.8% reduction in global warming potential can be achieved. The findings reveal that the developed DE-SHCC has the potential to facilitate sustainability and enhance the mechanical properties in construction 3D printing.