Development of sustainable strain-hardening cementitious composites containing diatomite for 3D printing

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 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.