This work aims to shape a hollow cylinder with a geopolymer and an additive manufacturing process (3D printing) without organic additives. The formulation of a geopolymer composite using only mineral parts is proposed and the parameters of the 3D printing process were optimized. The mechanical properties, the microstructure, and the adhesion of the layers of the printing material were analysed and compared with the literature.The results showed that the geopolymer composite could be printed with the addition of small ratios of wollastonite, glass fibers, or non-reactive aluminosilicate and by modifying the printing speed. The stacking layers exhibited a good adhesion between them, avoiding the socalled "cold joints" effect, and the fibers are flow-oriented during the process. Some hollow cylinders are successfully printed with a flexural strength of 15 MPa.

Highlights Geopolymer composites based on wollastonite and glass fibers were synthetized  Influence of the MK and additives on viscosity and working properties was studied  The wollastonite ensures a better dissolution of the metakaolin  The glass fibers act as an anchoring site during the geopolymerization reaction