Preparation and characterization of gypsum-based materials used for 3D robocasting

In this study, gypsum-based materials (GM) comprising mainly α-hemihydrate gypsum, polycarboxylate, hydroxypropyl methyl cellulose and starch ether were prepared and used for 3D robocasting (3DR). The setting time and rheological properties of the GM slurry and the physical properties of the GM sample, including bulk density, porosity and mechanical strength, were investigated. The results indicate that the GM slurry exhibits an obvious shear thinning behavior and a good shape fidelity. The measured dynamic yield stress, final viscosity and initial storage modulus of the GM slurry are as high as 420.73 Pa, 7.29 Pa s and 273.86 kPa, respectively. Meanwhile, the GM slurry presents an adequate initial setting time of 68 min compared with a printing time of 14 min. In addition, the GM sample prepared by 3DR has a high compressive strength of 64.96?±?5.98 MPa and a bending strength of 15.24?±?1.58 MPa. These mechanical strengths are comparable with those of the GM and pure gypsum plaster sample prepared by traditional molding. Generally, the 3DR of GM is a promising method to improve the mechanical strength of printed gypsum products and presents great application prospects in the building of complex large-scale structures.