A 2 K strategy for 3D printing of metakaolin-based geopolymers

The application of 3D printing in construction has the potential to revolutionize the industry, offering cost-efficiency, reduced manual labor, and minimized material waste, particularly with cementitious materials. While significant progress has been made in printing with alternative binders, challenges persist, especially with high-viscosity materials like metakaolin-based geopolymers. This paper presents a novel approach to address these challenges by leveraging 2K (two-component) printing systems, which excel in handling high-viscosity mixtures. We propose a formulation strategy tailored to metakaolin-based geopolymers for 2K systems. Initially, a base formulation is developed using a blend of flash-calcined and rotary kiln-calcined metakaolin to balance reactivity and pumpability. Empirical tests identified sulfoaluminates and plaster as efficient accelerators for metakaolin-based geopolymers. Sand packing was optimized to decrease the geopolymer binder quantity. The resulting formulation, requiring no heating, is successfully printed using the 2K printing system, offering a sustainable alternative to fly-ash geopolymers. Refining the injection process, improving the injection hardware such as the needle design and suspension fluid will pave the way for full-scale industrial application.