Development of CO2 curable 3D printing materials

In this paper, printable gamma-C2S slurries based on the carbonation of calcium silicate have been developed, and printability is demonstrated by the extrusion-based layer deposition. The gamma-C2S with low hydraulicity and uncondensed silica fume (SF) are used to prepare the slurry at a water/solid (w/s) ratio of 0.24. The printable behavior is controlled by three rheology modifying agent (RMA), including sodium carboxymethylcellulose (CMC), hydroxypropyl methylcellulose (HPMC), and polyacrylamide (PAM). The compressive strength and inter-layer bonding strength of the printed sample are 109.3 MPa and 4.9 MPa, respectively, after pre-drying to a w/s of 0.08 and 12 h carbonation under the CO2 pressure of 3 bar. The great mechanical property can be attributed to the diffusion of the carbonation reaction into the center of samples and the densification by the carbonation products. The printing-carbonation synergistic enhancement technique is proposed, where the printing process is carried out in a CO2 atmosphere, the carbonation reaction improves the yield stress of freshly printed structure and enhances the stability of the whole printed sample. Based on this technique, it is expected to achieve the independent design of extrudability and build-ability of printable slurry and significantly expand the diversity of the geometrical design of 3D printing structures.