Optimisation of mixture properties for 3D printing of geopolymer concrete

Freedom of design, customisation, automation, waste minimisation, reduced labour and building complex structures with cheaper materials are the main initiatives for developing 3D printed structures. The fresh properties of concrete are the most important aspects of a successful 3D printing. Concrete requires high workability for extrusion, optimum open time and high early strength in order to support the subsequent layers for 3D printing. Therefore, a mixture design that can satisfy these requirements is needed. Geopolymer concrete is a sustainable solution to traditional Portland cement-based concrete that uses waste materials. In addition, the controlled alkali-activation of geopolymer precursors in order to achieve optimum setting and workability compared to Portland cement provides freedom of mixture design for 3D printing. This paper will investigate the fresh properties of geopolymer mixtures in order to find an effective mixture that is compatible with 3D printing technology and can be also strong enough to stand as a structure. Rheology (workability), open time and compressive strength, as well as, printing parameters such as extrusion pressure and printhead speed was studied in order to achieve a successful geopolymer mixture for 3D printing.