Challenges in Enhancing Workability and Printability for 3D-Printable Geopolymer Mortar

Geopolymer concrete utilizing fly ash as an alternative to Portland cement is a focus in research aimed at reducing CO2 emissions. In some mix designs, geopolymer concrete sets rapidly limiting its open time which poses significant challenges to adoption. Furthermore, the use of 3D printing as a construction method has also seen increasing interest due to the potential time savings, but is not without its drawbacks. This paper explores the complexities associated with geopolymer concrete for 3D Concrete Printing (3DCP). The balance between workability and sustainability, essential for 3DCP success, necessitates precise mix designs. The global variations in aggregates, sizes, admixtures, and deposition methods add further intricacy to creating a standardized mix design.
The study addresses these challenges by developing a 3D printable mix design for geopolymer mortar. Specifically, the research formulates a geopolymer mortar with Class F fly ash for an air-pressurized 3DCP technique. Introducing sucrose as a set retarder enhances workability and printability in an intuitively developed mix design. Closer analysis, however, indicates sucrose reduces the fluidity of geopolymer mortar, and in some cases, results in drier mixes. Sucrose demonstrates the ability to modulate workability when properly paired with adequate water content and sand of an appropriate fineness ensuring successful application in the 3DCP process.
The findings offer valuable insights for future research and contribute to standardizing mix design methods for printable geopolymer mortars and concrete. This work aligns with broader initiatives to develop adaptable and alternative construction materials, specifically addressing challenges unique to 3DCP while promoting alternative materials that mitigate CO2 emissions.