Thermal and hydration properties of 3D printing gypsum materials incorporated with accelerators

3D printing technology, as a landmark technology for significant changes in modern manufacturing industry, has become an important means to lead the future of construction to achieve convenient, personalised, functional integration. In this study, alpha hemihydrate gypsum (alpha-HH) was used as the 3D printing matrix material, and the accelerators were introduced to match the slurry-based 3D printing process. The hydration heat and thermogravimetric changes were characterised to analyse the effect of accelerators on the thermal properties via thermogravimetry-differential scanning calorimetry (TG-DSC) analysis. Further, X-ray diffraction analysis (XRD) and morphological observations of the hardened gypsum were conducted to assess the impact of accelerators on the hydration process of alpha-HH. The results showed that all accelerators considerably reduced the hydration reaction time of alpha-HH, with the maximum exothermic peak observed in the order lithium sulphate (LS, 6.78 min) > sodium sulphate (NS, 11.33 min) > potassium sulphate (KS, 15.64 min) > control sample (26.43 min). Under the influence of KS, the proportion of dihydrate gypsum crystals reached 50.5% within 5 min of alpha-HH hydration. The addition of accelerators was shown to be effective for slurry-based 3D printing gypsum process.